all messages for Emacs-related lists mirrored at yhetil.org
 help / color / mirror / code / Atom feed
blob 185d355ba7096f3ef2d610c65ae3f2246fe7a17f 110998 bytes (raw)
name: doc/lispref/minibuf.texi 	 # note: path name is non-authoritative(*)

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
 
@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
@c Copyright (C) 1990--1995, 1998--1999, 2001--2021 Free Software
@c Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@node Minibuffers
@chapter Minibuffers
@cindex arguments, reading
@cindex complex arguments
@cindex minibuffer

  A @dfn{minibuffer} is a special buffer that Emacs commands use to
read arguments more complicated than the single numeric prefix
argument.  These arguments include file names, buffer names, and
command names (as in @kbd{M-x}).  The minibuffer is displayed on the
bottom line of the frame, in the same place as the echo area
(@pxref{The Echo Area}), but only while it is in use for reading an
argument.

@menu
* Intro to Minibuffers::      Basic information about minibuffers.
* Text from Minibuffer::      How to read a straight text string.
* Object from Minibuffer::    How to read a Lisp object or expression.
* Minibuffer History::        Recording previous minibuffer inputs
                                so the user can reuse them.
* Initial Input::             Specifying initial contents for the minibuffer.
* Completion::                How to invoke and customize completion.
* Yes-or-No Queries::         Asking a question with a simple answer.
* Multiple Queries::          Asking complex questions.
* Reading a Password::        Reading a password from the terminal.
* Minibuffer Commands::       Commands used as key bindings in minibuffers.
* Minibuffer Windows::        Operating on the special minibuffer windows.
* Minibuffer Contents::       How such commands access the minibuffer text.
* Recursive Mini::            Whether recursive entry to minibuffer is allowed.
* Inhibiting Interaction::    Running Emacs when no interaction is possible.
* Minibuffer Misc::           Various customization hooks and variables.
@end menu

@node Intro to Minibuffers
@section Introduction to Minibuffers

  In most ways, a minibuffer is a normal Emacs buffer.  Most operations
@emph{within} a buffer, such as editing commands, work normally in a
minibuffer.  However, many operations for managing buffers do not apply
to minibuffers.  The name of a minibuffer always has the form @w{@samp{
*Minibuf-@var{number}*}}, and it cannot be changed.  Minibuffers are
displayed only in special windows used only for minibuffers; these
windows always appear at the bottom of a frame.  (Sometimes frames have
no minibuffer window, and sometimes a special kind of frame contains
nothing but a minibuffer window; see @ref{Minibuffers and Frames}.)

  The text in the minibuffer always starts with the @dfn{prompt string},
the text that was specified by the program that is using the minibuffer
to tell the user what sort of input to type.  This text is marked
read-only so you won't accidentally delete or change it.  It is also
marked as a field (@pxref{Fields}), so that certain motion functions,
including @code{beginning-of-line}, @code{forward-word},
@code{forward-sentence}, and @code{forward-paragraph}, stop at the
boundary between the prompt and the actual text.

@c See https://debbugs.gnu.org/11276
  The minibuffer's window is normally a single line; it grows
automatically if the contents require more space.  Whilst the minibuffer
is active, you can explicitly resize its window temporarily with the
window sizing commands; the window reverts to its normal size when the
minibuffer is exited.  When the minibuffer is not active, you can resize
its window permanently by using the window sizing commands in the
frame's other window, or dragging the mode line with the mouse.  (Due to
details of the current implementation, for this to work
@code{resize-mini-windows} must be @code{nil}.)  If the frame contains
just a minibuffer window, you can change its size by changing the
frame's size.

  Use of the minibuffer reads input events, and that alters the values
of variables such as @code{this-command} and @code{last-command}
(@pxref{Command Loop Info}).  Your program should bind them around the
code that uses the minibuffer, if you do not want that to change them.

  Under some circumstances, a command can use a minibuffer even if
there is an active minibuffer; such a minibuffer is called a
@dfn{recursive minibuffer}.  The first minibuffer is named
@w{@samp{ *Minibuf-1*}}.  Recursive minibuffers are named by
incrementing the number at the end of the name.  (The names begin with
a space so that they won't show up in normal buffer lists.)  Of
several recursive minibuffers, the innermost (or most recently
entered) is the @dfn{active minibuffer}--it is the one you can
terminate by typing @key{RET} (@code{exit-minibuffer}) in.  We usually
call this @emph{the} minibuffer.  You can permit or forbid recursive
minibuffers by setting the variable
@code{enable-recursive-minibuffers}, or by putting properties of that
name on command symbols (@xref{Recursive Mini}.)

  Like other buffers, a minibuffer uses a local keymap
(@pxref{Keymaps}) to specify special key bindings.  The function that
invokes the minibuffer also sets up its local map according to the job
to be done.  @xref{Text from Minibuffer}, for the non-completion
minibuffer local maps.  @xref{Completion Commands}, for the minibuffer
local maps for completion.

@cindex inactive minibuffer
  When a minibuffer is inactive, its major mode is
@code{minibuffer-inactive-mode}, with keymap
@code{minibuffer-inactive-mode-map}.  This is only really useful if
the minibuffer is in a separate frame.  @xref{Minibuffers and Frames}.

  When Emacs is running in batch mode, any request to read from the
minibuffer actually reads a line from the standard input descriptor that
was supplied when Emacs was started.  This supports only basic input:
none of the special minibuffer features (history, completion, etc.)@:
are available in batch mode.

@node Text from Minibuffer
@section Reading Text Strings with the Minibuffer
@cindex minibuffer input, reading text strings

  The most basic primitive for minibuffer input is
@code{read-from-minibuffer}, which can be used to read either a string
or a Lisp object in textual form.  The function @code{read-regexp} is
used for reading regular expressions (@pxref{Regular Expressions}),
which are a special kind of string.  There are also specialized
functions for reading commands, variables, file names, etc.@:
(@pxref{Completion}).

  In most cases, you should not call minibuffer input functions in the
middle of a Lisp function.  Instead, do all minibuffer input as part of
reading the arguments for a command, in the @code{interactive}
specification.  @xref{Defining Commands}.

@defun read-from-minibuffer prompt &optional initial keymap read history default inherit-input-method
This function is the most general way to get input from the
minibuffer.  By default, it accepts arbitrary text and returns it as a
string; however, if @var{read} is non-@code{nil}, then it uses
@code{read} to convert the text into a Lisp object (@pxref{Input
Functions}).

The first thing this function does is to activate a minibuffer and
display it with @var{prompt} (which must be a string) as the
prompt.  Then the user can edit text in the minibuffer.

When the user types a command to exit the minibuffer,
@code{read-from-minibuffer} constructs the return value from the text in
the minibuffer.  Normally it returns a string containing that text.
However, if @var{read} is non-@code{nil}, @code{read-from-minibuffer}
reads the text and returns the resulting Lisp object, unevaluated.
(@xref{Input Functions}, for information about reading.)

@cindex future history in minibuffer input
The argument @var{default} specifies default values to make available
through the history commands.  It should be a string, a list of
strings, or @code{nil}.  The string or strings become the minibuffer's
``future history'', available to the user with @kbd{M-n}.

If @var{read} is non-@code{nil}, then @var{default} is also used
as the input to @code{read}, if the user enters empty input.
If @var{default} is a list of strings, the first string is used as the input.
If @var{default} is @code{nil}, empty input results in an @code{end-of-file} error.
However, in the usual case (where @var{read} is @code{nil}),
@code{read-from-minibuffer} ignores @var{default} when the user enters
empty input and returns an empty string, @code{""}.  In this respect,
it differs from all the other minibuffer input functions in this chapter.

If @var{keymap} is non-@code{nil}, that keymap is the local keymap to
use in the minibuffer.  If @var{keymap} is omitted or @code{nil}, the
value of @code{minibuffer-local-map} is used as the keymap.  Specifying
a keymap is the most important way to customize the minibuffer for
various applications such as completion.

The argument @var{history} specifies a history list variable to use
for saving the input and for history commands used in the minibuffer.
It defaults to @code{minibuffer-history}.  You can optionally specify
a starting position in the history list as well.  @xref{Minibuffer History}.

If the variable @code{minibuffer-allow-text-properties} is
non-@code{nil}, then the string that is returned includes whatever text
properties were present in the minibuffer.  Otherwise all the text
properties are stripped when the value is returned.

@vindex minibuffer-prompt-properties
The text properties in @code{minibuffer-prompt-properties} are applied
to the prompt.  By default, this property list defines a face to use
for the prompt.  This face, if present, is applied to the end of the
face list and merged before display.

If the user wants to completely control the look of the prompt, the
most convenient way to do that is to specify the @code{default} face
at the end of all face lists.  For instance:

@lisp
(read-from-minibuffer
 (concat
  (propertize "Bold" 'face '(bold default))
  (propertize " and normal: " 'face '(default))))
@end lisp

If the argument @var{inherit-input-method} is non-@code{nil}, then the
minibuffer inherits the current input method (@pxref{Input Methods}) and
the setting of @code{enable-multibyte-characters} (@pxref{Text
Representations}) from whichever buffer was current before entering the
minibuffer.

Use of @var{initial} is mostly deprecated; we recommend using
a non-@code{nil} value only in conjunction with specifying a cons cell
for @var{history}.  @xref{Initial Input}.
@end defun

@defun read-string prompt &optional initial history default inherit-input-method
This function reads a string from the minibuffer and returns it.  The
arguments @var{prompt}, @var{initial}, @var{history} and
@var{inherit-input-method} are used as in @code{read-from-minibuffer}.
The keymap used is @code{minibuffer-local-map}.

The optional argument @var{default} is used as in
@code{read-from-minibuffer}, except that, if non-@code{nil}, it also
specifies a default value to return if the user enters null input.  As
in @code{read-from-minibuffer} it should be a string, a list of
strings, or @code{nil}, which is equivalent to an empty string.  When
@var{default} is a string, that string is the default value.  When it
is a list of strings, the first string is the default value.  (All
these strings are available to the user in the ``future minibuffer
history''.)

This function works by calling the
@code{read-from-minibuffer} function:

@smallexample
@group
(read-string @var{prompt} @var{initial} @var{history} @var{default} @var{inherit})
@equiv{}
(let ((value
       (read-from-minibuffer @var{prompt} @var{initial} nil nil
                             @var{history} @var{default} @var{inherit})))
  (if (and (equal value "") @var{default})
      (if (consp @var{default}) (car @var{default}) @var{default})
    value))
@end group
@end smallexample
@end defun

@defun read-regexp prompt &optional defaults history
This function reads a regular expression as a string from the
minibuffer and returns it.  If the minibuffer prompt string
@var{prompt} does not end in @samp{:} (followed by optional
whitespace), the function adds @samp{: } to the end, preceded by the
default return value (see below), if that is non-empty.

The optional argument @var{defaults} controls the default value to
return if the user enters null input, and should be one of: a string;
@code{nil}, which is equivalent to an empty string; a list of strings;
or a symbol.

If @var{defaults} is a symbol, @code{read-regexp} consults the value
of the variable @code{read-regexp-defaults-function} (see below), and
if that is non-@code{nil} uses it in preference to @var{defaults}.
The value in this case should be either:

@itemize @minus
@item
@code{regexp-history-last}, which means to use the first element of
the appropriate minibuffer history list (see below).

@item
A function of no arguments, whose return value (which should be
@code{nil}, a string, or a list of strings) becomes the value of
@var{defaults}.
@end itemize

@code{read-regexp} now ensures that the result of processing
@var{defaults} is a list (i.e., if the value is @code{nil} or a
string, it converts it to a list of one element).  To this list,
@code{read-regexp} then appends a few potentially useful candidates for
input.  These are:

@itemize @minus
@item
The word or symbol at point.
@item
The last regexp used in an incremental search.
@item
The last string used in an incremental search.
@item
The last string or pattern used in query-replace commands.
@end itemize

The function now has a list of regular expressions that it passes to
@code{read-from-minibuffer} to obtain the user's input.  The first
element of the list is the default result in case of empty input.  All
elements of the list are available to the user as the ``future
minibuffer history'' list (@pxref{Minibuffer History, future list,,
emacs, The GNU Emacs Manual}).

The optional argument @var{history}, if non-@code{nil}, is a symbol
specifying a minibuffer history list to use (@pxref{Minibuffer
History}).  If it is omitted or @code{nil}, the history list defaults
to @code{regexp-history}.
@end defun

@defopt read-regexp-defaults-function
The function @code{read-regexp} may use the value of this variable to
determine its list of default regular expressions.  If non-@code{nil},
the value of this variable should be either:

@itemize @minus
@item
The symbol @code{regexp-history-last}.

@item
A function of no arguments that returns either @code{nil}, a string,
or a list of strings.
@end itemize

@noindent
See @code{read-regexp} above for details of how these values are used.
@end defopt

@defvar minibuffer-allow-text-properties
If this variable is @code{nil}, then @code{read-from-minibuffer}
and @code{read-string} strip all text properties from the minibuffer
input before returning it.  However,
@code{read-no-blanks-input} (see below), as well as
@code{read-minibuffer} and related functions (@pxref{Object from
Minibuffer,, Reading Lisp Objects With the Minibuffer}), and all
functions that do minibuffer input with completion, remove the @code{face}
property unconditionally, regardless of the value of this variable.

If this variable is non-@code{nil}, most text properties on strings
from the completion table are preserved---but only on the part of the
strings that were completed.

@lisp
(let ((minibuffer-allow-text-properties t))
  (completing-read "String: " (list (propertize "foobar" 'data 'zot))))
=> #("foobar" 3 6 (data zot))
@end lisp

In this example, the user typed @samp{foo} and then hit the @kbd{TAB}
key, so the text properties are only preserved on the last three
characters.
@end defvar

@defvar minibuffer-local-map
This
@anchor{Definition of minibuffer-local-map}
@c avoid page break at anchor; work around Texinfo deficiency
is the default local keymap for reading from the minibuffer.  By
default, it makes the following bindings:

@table @asis
@item @kbd{C-j}
@code{exit-minibuffer}

@item @key{RET}
@code{exit-minibuffer}

@item @kbd{M-<}
@code{minibuffer-beginning-of-buffer}

@item @kbd{C-g}
@code{abort-recursive-edit}

@item @kbd{M-n}
@itemx @key{DOWN}
@code{next-history-element}

@item @kbd{M-p}
@itemx @key{UP}
@code{previous-history-element}

@item @kbd{M-s}
@code{next-matching-history-element}

@item @kbd{M-r}
@code{previous-matching-history-element}

@ignore
@c Does not seem worth/appropriate mentioning.
@item @kbd{C-@key{TAB}}
@code{file-cache-minibuffer-complete}
@end ignore
@end table
@end defvar

@c In version 18, initial is required
@c Emacs 19 feature
@defun read-no-blanks-input prompt &optional initial inherit-input-method
This function reads a string from the minibuffer, but does not allow
whitespace characters as part of the input: instead, those characters
terminate the input.  The arguments @var{prompt}, @var{initial}, and
@var{inherit-input-method} are used as in @code{read-from-minibuffer}.

This is a simplified interface to the @code{read-from-minibuffer}
function, and passes the value of the @code{minibuffer-local-ns-map}
keymap as the @var{keymap} argument for that function.  Since the keymap
@code{minibuffer-local-ns-map} does not rebind @kbd{C-q}, it @emph{is}
possible to put a space into the string, by quoting it.

This function discards text properties, regardless of the value of
@code{minibuffer-allow-text-properties}.

@smallexample
@group
(read-no-blanks-input @var{prompt} @var{initial})
@equiv{}
(let (minibuffer-allow-text-properties)
  (read-from-minibuffer @var{prompt} @var{initial} minibuffer-local-ns-map))
@end group
@end smallexample
@end defun

@c Slightly unfortunate name, suggesting it might be related to the
@c Nextstep port...
@defvar minibuffer-local-ns-map
This built-in variable is the keymap used as the minibuffer local keymap
in the function @code{read-no-blanks-input}.  By default, it makes the
following bindings, in addition to those of @code{minibuffer-local-map}:

@table @asis
@item @key{SPC}
@cindex @key{SPC} in minibuffer
@code{exit-minibuffer}

@item @key{TAB}
@cindex @key{TAB} in minibuffer
@code{exit-minibuffer}

@item @kbd{?}
@cindex @kbd{?} in minibuffer
@code{self-insert-and-exit}
@end table
@end defvar

@vindex minibuffer-default-prompt-format
@defun format-prompt prompt default &rest format-args
Format @var{prompt} with default value @var{default} according to the
@code{minibuffer-default-prompt-format} variable.

@code{minibuffer-default-prompt-format} is a format string (defaulting
to @samp{" (default %s)"} that says how the ``default'' bit in prompts
like @samp{"Local filename (default somefile): "} are to be formatted.

To allow the users to customize how this is displayed, code that
prompts the user for a value (and has a default) should look something
along the lines of this code snippet:

@lisp
(read-file-name
 (format-prompt "Local filename" file)
 nil file)
@end lisp

If @var{format-args} is @code{nil}, @var{prompt} is used as a literal
string.  If @var{format-args} is non-@code{nil}, @var{prompt} is used
as a format control string, and @var{prompt} and @var{format-args} are
passed to @code{format} (@pxref{Formatting Strings}).

@code{minibuffer-default-prompt-format} can be @samp{""}, in which
case no default values are displayed.

If @var{default} is @code{nil}, there is no default value, and
therefore no ``default value'' string is included in the result value.
If @var{default} is a non-@code{nil} list, the first element of the
list is used in the prompt.
@end defun

@node Object from Minibuffer
@section Reading Lisp Objects with the Minibuffer
@cindex minibuffer input, reading lisp objects

  This section describes functions for reading Lisp objects with the
minibuffer.

@defun read-minibuffer prompt &optional initial
This function reads a Lisp object using the minibuffer, and returns it
without evaluating it.  The arguments @var{prompt} and @var{initial} are
used as in @code{read-from-minibuffer}.

This is a simplified interface to the
@code{read-from-minibuffer} function:

@smallexample
@group
(read-minibuffer @var{prompt} @var{initial})
@equiv{}
(let (minibuffer-allow-text-properties)
  (read-from-minibuffer @var{prompt} @var{initial} nil t))
@end group
@end smallexample

Here is an example in which we supply the string @code{"(testing)"} as
initial input:

@smallexample
@group
(read-minibuffer
 "Enter an expression: " (format "%s" '(testing)))

;; @r{Here is how the minibuffer is displayed:}
@end group

@group
---------- Buffer: Minibuffer ----------
Enter an expression: (testing)@point{}
---------- Buffer: Minibuffer ----------
@end group
@end smallexample

@noindent
The user can type @key{RET} immediately to use the initial input as a
default, or can edit the input.
@end defun

@defun eval-minibuffer prompt &optional initial
This function reads a Lisp expression using the minibuffer, evaluates
it, then returns the result.  The arguments @var{prompt} and
@var{initial} are used as in @code{read-from-minibuffer}.

This function simply evaluates the result of a call to
@code{read-minibuffer}:

@smallexample
@group
(eval-minibuffer @var{prompt} @var{initial})
@equiv{}
(eval (read-minibuffer @var{prompt} @var{initial}))
@end group
@end smallexample
@end defun

@defun edit-and-eval-command prompt form
This function reads a Lisp expression in the minibuffer, evaluates it,
then returns the result.  The difference between this command and
@code{eval-minibuffer} is that here the initial @var{form} is not
optional and it is treated as a Lisp object to be converted to printed
representation rather than as a string of text.  It is printed with
@code{prin1}, so if it is a string, double-quote characters (@samp{"})
appear in the initial text.  @xref{Output Functions}.

In the following example, we offer the user an expression with initial
text that is already a valid form:

@smallexample
@group
(edit-and-eval-command "Please edit: " '(forward-word 1))

;; @r{After evaluation of the preceding expression,}
;;   @r{the following appears in the minibuffer:}
@end group

@group
---------- Buffer: Minibuffer ----------
Please edit: (forward-word 1)@point{}
---------- Buffer: Minibuffer ----------
@end group
@end smallexample

@noindent
Typing @key{RET} right away would exit the minibuffer and evaluate the
expression, thus moving point forward one word.
@end defun

@node Minibuffer History
@section Minibuffer History
@cindex minibuffer history
@cindex history list

  A @dfn{minibuffer history list} records previous minibuffer inputs
so the user can reuse them conveniently.  It is a variable whose value
is a list of strings (previous inputs), most recent first.

  There are many separate minibuffer history lists, used for different
kinds of inputs.  It's the Lisp programmer's job to specify the right
history list for each use of the minibuffer.

  You specify a minibuffer history list with the optional @var{history}
argument to @code{read-from-minibuffer} or @code{completing-read}.
Here are the possible values for it:

@table @asis
@item @var{variable}
Use @var{variable} (a symbol) as the history list.

@item (@var{variable} . @var{startpos})
Use @var{variable} (a symbol) as the history list, and assume that the
initial history position is @var{startpos} (a nonnegative integer).

Specifying 0 for @var{startpos} is equivalent to just specifying the
symbol @var{variable}.  @code{previous-history-element} will display
the most recent element of the history list in the minibuffer.  If you
specify a positive @var{startpos}, the minibuffer history functions
behave as if @code{(elt @var{variable} (1- @var{startpos}))} were the
history element currently shown in the minibuffer.

For consistency, you should also specify that element of the history
as the initial minibuffer contents, using the @var{initial} argument
to the minibuffer input function (@pxref{Initial Input}).
@end table

  If you don't specify @var{history}, then the default history list
@code{minibuffer-history} is used.  For other standard history lists,
see below.  You can also create your own history list variable; just
initialize it to @code{nil} before the first use.  If the variable is
buffer local, then each buffer will have its own input history list.

  Both @code{read-from-minibuffer} and @code{completing-read} add new
elements to the history list automatically, and provide commands to
allow the user to reuse items on the list.  The only thing your program
needs to do to use a history list is to initialize it and to pass its
name to the input functions when you wish.  But it is safe to modify the
list by hand when the minibuffer input functions are not using it.

  Emacs functions that add a new element to a history list can also
delete old elements if the list gets too long.  The variable
@code{history-length} specifies the maximum length for most history
lists.  To specify a different maximum length for a particular history
list, put the length in the @code{history-length} property of the
history list symbol.  The variable @code{history-delete-duplicates}
specifies whether to delete duplicates in history.

@defun add-to-history history-var newelt &optional maxelt keep-all
This function adds a new element @var{newelt}, if it isn't the empty
string, to the history list stored in the variable @var{history-var},
and returns the updated history list.  It limits the list length to
the value of @var{maxelt} (if non-@code{nil}) or @code{history-length}
(described below).  The possible values of @var{maxelt} have the same
meaning as the values of @code{history-length}.
@var{history-var} cannot refer to a lexical variable.

Normally, @code{add-to-history} removes duplicate members from the
history list if @code{history-delete-duplicates} is non-@code{nil}.
However, if @var{keep-all} is non-@code{nil}, that says not to remove
duplicates, and to add @var{newelt} to the list even if it is empty.
@end defun

@defvar history-add-new-input
If the value of this variable is @code{nil}, standard functions that
read from the minibuffer don't add new elements to the history list.
This lets Lisp programs explicitly manage input history by using
@code{add-to-history}.  The default value is @code{t}.
@end defvar

@defopt history-length
The value of this variable specifies the maximum length for all
history lists that don't specify their own maximum lengths.  If the
value is @code{t}, that means there is no maximum (don't delete old
elements).  If a history list variable's symbol has a non-@code{nil}
@code{history-length} property, it overrides this variable for that
particular history list.
@end defopt

@defopt history-delete-duplicates
If the value of this variable is @code{t}, that means when adding a
new history element, all previous identical elements are deleted.
@end defopt

  Here are some of the standard minibuffer history list variables:

@defvar minibuffer-history
The default history list for minibuffer history input.
@end defvar

@defvar query-replace-history
A history list for arguments to @code{query-replace} (and similar
arguments to other commands).
@end defvar

@defvar file-name-history
A history list for file-name arguments.
@end defvar

@defvar buffer-name-history
A history list for buffer-name arguments.
@end defvar

@defvar regexp-history
A history list for regular expression arguments.
@end defvar

@defvar extended-command-history
A history list for arguments that are names of extended commands.
@end defvar

@defvar shell-command-history
A history list for arguments that are shell commands.
@end defvar

@defvar read-expression-history
A history list for arguments that are Lisp expressions to evaluate.
@end defvar

@defvar face-name-history
A history list for arguments that are faces.
@end defvar

@findex read-variable@r{, history list}
@defvar custom-variable-history
A history list for variable-name arguments read by
@code{read-variable}.
@end defvar

@defvar read-number-history
A history list for numbers read by @code{read-number}.
@end defvar

@defvar goto-line-history
A history list for arguments to @code{goto-line}.  This variable is
buffer local.
@end defvar

@c Less common: coding-system-history, input-method-history,
@c command-history, grep-history, grep-find-history,
@c read-envvar-name-history, setenv-history, yes-or-no-p-history.

@node Initial Input
@section Initial Input

Several of the functions for minibuffer input have an argument called
@var{initial}.  This is a mostly-deprecated
feature for specifying that the minibuffer should start out with
certain text, instead of empty as usual.

If @var{initial} is a string, the minibuffer starts out containing the
text of the string, with point at the end, when the user starts to
edit the text.  If the user simply types @key{RET} to exit the
minibuffer, it will use the initial input string to determine the
value to return.

@strong{We discourage use of a non-@code{nil} value for
@var{initial}}, because initial input is an intrusive interface.
History lists and default values provide a much more convenient method
to offer useful default inputs to the user.

There is just one situation where you should specify a string for an
@var{initial} argument.  This is when you specify a cons cell for the
@var{history} argument.  @xref{Minibuffer History}.

@var{initial} can also be a cons cell of the form @code{(@var{string}
. @var{position})}.  This means to insert @var{string} in the
minibuffer but put point at @var{position} within the string's text.

As a historical accident, @var{position} was implemented
inconsistently in different functions.  In @code{completing-read},
@var{position}'s value is interpreted as origin-zero; that is, a value
of 0 means the beginning of the string, 1 means after the first
character, etc.  In @code{read-minibuffer}, and the other
non-completion minibuffer input functions that support this argument,
1 means the beginning of the string, 2 means after the first character,
etc.

Use of a cons cell as the value for @var{initial} arguments is deprecated.

@node Completion
@section Completion
@cindex completion

  @dfn{Completion} is a feature that fills in the rest of a name
starting from an abbreviation for it.  Completion works by comparing the
user's input against a list of valid names and determining how much of
the name is determined uniquely by what the user has typed.  For
example, when you type @kbd{C-x b} (@code{switch-to-buffer}) and then
@c "This is the sort of English up with which I will not put."
type the first few letters of the name of the buffer to which you wish
to switch, and then type @key{TAB} (@code{minibuffer-complete}), Emacs
extends the name as far as it can.

  Standard Emacs commands offer completion for names of symbols, files,
buffers, and processes; with the functions in this section, you can
implement completion for other kinds of names.

  The @code{try-completion} function is the basic primitive for
completion: it returns the longest determined completion of a given
initial string, with a given set of strings to match against.

  The function @code{completing-read} provides a higher-level interface
for completion.  A call to @code{completing-read} specifies how to
determine the list of valid names.  The function then activates the
minibuffer with a local keymap that binds a few keys to commands useful
for completion.  Other functions provide convenient simple interfaces
for reading certain kinds of names with completion.

@menu
* Basic Completion::       Low-level functions for completing strings.
* Minibuffer Completion::  Invoking the minibuffer with completion.
* Completion Commands::    Minibuffer commands that do completion.
* High-Level Completion::  Convenient special cases of completion
                             (reading buffer names, variable names, etc.).
* Reading File Names::     Using completion to read file names and
                             shell commands.
* Completion Variables::   Variables controlling completion behavior.
* Programmed Completion::  Writing your own completion function.
* Completion in Buffers::  Completing text in ordinary buffers.
@end menu

@node Basic Completion
@subsection Basic Completion Functions

  The following completion functions have nothing in themselves to do
with minibuffers.  We describe them here to keep them near the
higher-level completion features that do use the minibuffer.

@defun try-completion string collection &optional predicate
This function returns the longest common substring of all possible
completions of @var{string} in @var{collection}.

@cindex completion table
@var{collection} is called the @dfn{completion table}.  Its value must
be a list of strings or cons cells, an obarray, a hash table, or a
completion function.

@code{try-completion} compares @var{string} against each of the
permissible completions specified by the completion table.  If no
permissible completions match, it returns @code{nil}.  If there is
just one matching completion, and the match is exact, it returns
@code{t}.  Otherwise, it returns the longest initial sequence common
to all possible matching completions.

If @var{collection} is a list, the permissible completions are
specified by the elements of the list, each of which should be either
a string, or a cons cell whose @sc{car} is either a string or a symbol
(a symbol is converted to a string using @code{symbol-name}).  If the
list contains elements of any other type, those are ignored.

@cindex obarray in completion
If @var{collection} is an obarray (@pxref{Creating Symbols}), the names
of all symbols in the obarray form the set of permissible completions.

If @var{collection} is a hash table, then the keys that are strings or
symbols are the possible completions.  Other keys are ignored.

You can also use a function as @var{collection}.  Then the function is
solely responsible for performing completion; @code{try-completion}
returns whatever this function returns.  The function is called with
three arguments: @var{string}, @var{predicate} and @code{nil} (the
third argument is so that the same function can be used
in @code{all-completions} and do the appropriate thing in either
case).  @xref{Programmed Completion}.

If the argument @var{predicate} is non-@code{nil}, then it must be a
function of one argument, unless @var{collection} is a hash table, in
which case it should be a function of two arguments.  It is used to
test each possible match, and the match is accepted only if
@var{predicate} returns non-@code{nil}.  The argument given to
@var{predicate} is either a string or a cons cell (the @sc{car} of
which is a string) from the alist, or a symbol (@emph{not} a symbol
name) from the obarray.  If @var{collection} is a hash table,
@var{predicate} is called with two arguments, the string key and the
associated value.

In addition, to be acceptable, a completion must also match all the
regular expressions in @code{completion-regexp-list}.  (Unless
@var{collection} is a function, in which case that function has to
handle @code{completion-regexp-list} itself.)

In the first of the following examples, the string @samp{foo} is
matched by three of the alist @sc{car}s.  All of the matches begin with
the characters @samp{fooba}, so that is the result.  In the second
example, there is only one possible match, and it is exact, so the
return value is @code{t}.

@smallexample
@group
(try-completion
 "foo"
 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4)))
     @result{} "fooba"
@end group

@group
(try-completion "foo" '(("barfoo" 2) ("foo" 3)))
     @result{} t
@end group
@end smallexample

In the following example, numerous symbols begin with the characters
@samp{forw}, and all of them begin with the word @samp{forward}.  In
most of the symbols, this is followed with a @samp{-}, but not in all,
so no more than @samp{forward} can be completed.

@smallexample
@group
(try-completion "forw" obarray)
     @result{} "forward"
@end group
@end smallexample

Finally, in the following example, only two of the three possible
matches pass the predicate @code{test} (the string @samp{foobaz} is
too short).  Both of those begin with the string @samp{foobar}.

@smallexample
@group
(defun test (s)
  (> (length (car s)) 6))
     @result{} test
@end group
@group
(try-completion
 "foo"
 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
 'test)
     @result{} "foobar"
@end group
@end smallexample
@end defun

@c Removed obsolete argument nospace.
@defun all-completions string collection &optional predicate
This function returns a list of all possible completions of
@var{string}.  The arguments to this function
@c (aside from @var{nospace})
are the same as those of @code{try-completion}, and it
uses @code{completion-regexp-list} in the same way that
@code{try-completion} does.

@ignore
The optional argument @var{nospace} is obsolete.  If it is
non-@code{nil}, completions that start with a space are ignored unless
@var{string} starts with a space.
@end ignore

If @var{collection} is a function, it is called with three arguments:
@var{string}, @var{predicate} and @code{t}; then @code{all-completions}
returns whatever the function returns.  @xref{Programmed Completion}.

Here is an example, using the function @code{test} shown in the
example for @code{try-completion}:

@smallexample
@group
(defun test (s)
  (> (length (car s)) 6))
     @result{} test
@end group

@group
(all-completions
 "foo"
 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
 'test)
     @result{} ("foobar1" "foobar2")
@end group
@end smallexample
@end defun

@defun test-completion string collection &optional predicate
@anchor{Definition of test-completion}
This function returns non-@code{nil} if @var{string} is a valid
completion alternative specified by @var{collection} and
@var{predicate}.  The arguments are the same as in
@code{try-completion}.  For instance, if @var{collection} is a list of
strings, this is true if @var{string} appears in the list and
@var{predicate} is satisfied.

This function uses @code{completion-regexp-list} in the same
way that @code{try-completion} does.

If @var{predicate} is non-@code{nil} and if @var{collection} contains
several strings that are equal to each other, as determined by
@code{compare-strings} according to @code{completion-ignore-case},
then @var{predicate} should accept either all or none of them.
Otherwise, the return value of @code{test-completion} is essentially
unpredictable.

If @var{collection} is a function, it is called with three arguments,
the values @var{string}, @var{predicate} and @code{lambda}; whatever
it returns, @code{test-completion} returns in turn.
@end defun

@defun completion-boundaries string collection predicate suffix
This function returns the boundaries of the field on which @var{collection}
will operate, assuming that @var{string} holds the text before point
and @var{suffix} holds the text after point.

Normally completion operates on the whole string, so for all normal
collections, this will always return @code{(0 . (length
@var{suffix}))}.  But more complex completion such as completion on
files is done one field at a time.  For example, completion of
@code{"/usr/sh"} will include @code{"/usr/share/"} but not
@code{"/usr/share/doc"} even if @code{"/usr/share/doc"} exists.
Also @code{all-completions} on @code{"/usr/sh"} will not include
@code{"/usr/share/"} but only @code{"share/"}.  So if @var{string} is
@code{"/usr/sh"} and @var{suffix} is @code{"e/doc"},
@code{completion-boundaries} will return @code{(5 . 1)} which tells us
that the @var{collection} will only return completion information that
pertains to the area after @code{"/usr/"} and before @code{"/doc"}.
@end defun

If you store a completion alist in a variable, you should mark the
variable as risky by giving it a non-@code{nil}
@code{risky-local-variable} property.  @xref{File Local Variables}.

@defvar completion-ignore-case
If the value of this variable is non-@code{nil}, case is not
considered significant in completion.  Within @code{read-file-name},
this variable is overridden by
@code{read-file-name-completion-ignore-case} (@pxref{Reading File
Names}); within @code{read-buffer}, it is overridden by
@code{read-buffer-completion-ignore-case} (@pxref{High-Level
Completion}).
@end defvar

@defvar completion-regexp-list
This is a list of regular expressions.  The completion functions only
consider a completion acceptable if it matches all regular expressions
in this list, with @code{case-fold-search} (@pxref{Searching and Case})
bound to the value of @code{completion-ignore-case}.
@end defvar

@defmac lazy-completion-table var fun
This macro provides a way to initialize the variable @var{var} as a
collection for completion in a lazy way, not computing its actual
contents until they are first needed.  You use this macro to produce a
value that you store in @var{var}.  The actual computation of the
proper value is done the first time you do completion using @var{var}.
It is done by calling @var{fun} with no arguments.  The
value @var{fun} returns becomes the permanent value of @var{var}.

Here is an example:

@smallexample
(defvar foo (lazy-completion-table foo make-my-alist))
@end smallexample
@end defmac

@c FIXME?  completion-table-with-context?
@findex completion-table-case-fold
@findex completion-table-in-turn
@findex completion-table-merge
@findex completion-table-subvert
@findex completion-table-with-quoting
@findex completion-table-with-predicate
@findex completion-table-with-terminator
@cindex completion table, modifying
@cindex completion tables, combining
There are several functions that take an existing completion table and
return a modified version.  @code{completion-table-case-fold} returns
a case-insensitive table.  @code{completion-table-in-turn} and
@code{completion-table-merge} combine multiple input tables in
different ways.  @code{completion-table-subvert} alters a table to use
a different initial prefix.  @code{completion-table-with-quoting}
returns a table suitable for operating on quoted text.
@code{completion-table-with-predicate} filters a table with a
predicate function.  @code{completion-table-with-terminator} adds a
terminating string.


@node Minibuffer Completion
@subsection Completion and the Minibuffer
@cindex minibuffer completion
@cindex reading from minibuffer with completion

  This section describes the basic interface for reading from the
minibuffer with completion.

@defun completing-read prompt collection &optional predicate require-match initial history default inherit-input-method
This function reads a string in the minibuffer, assisting the user by
providing completion.  It activates the minibuffer with prompt
@var{prompt}, which must be a string.

The actual completion is done by passing the completion table
@var{collection} and the completion predicate @var{predicate} to the
function @code{try-completion} (@pxref{Basic Completion}).  This
happens in certain commands bound in the local keymaps used for
completion.  Some of these commands also call @code{test-completion}.
Thus, if @var{predicate} is non-@code{nil}, it should be compatible
with @var{collection} and @code{completion-ignore-case}.
@xref{Definition of test-completion}.

@xref{Programmed Completion}, for detailed requirements when
@var{collection} is a function.

The value of the optional argument @var{require-match} determines how
the user may exit the minibuffer:

@itemize @bullet
@item
If @code{nil}, the usual minibuffer exit commands work regardless of
the input in the minibuffer.

@item
If @code{t}, the usual minibuffer exit commands won't exit unless the
input completes to an element of @var{collection}.

@item
If @code{confirm}, the user can exit with any input, but is asked for
confirmation if the input is not an element of @var{collection}.

@item
If @code{confirm-after-completion}, the user can exit with any input,
but is asked for confirmation if the preceding command was a
completion command (i.e., one of the commands in
@code{minibuffer-confirm-exit-commands}) and the resulting input is
not an element of @var{collection}.  @xref{Completion Commands}.

@item
Any other value of @var{require-match} behaves like @code{t}, except
that the exit commands won't exit if it performs completion.
@end itemize

However, empty input is always permitted, regardless of the value of
@var{require-match}; in that case, @code{completing-read} returns the
first element of @var{default}, if it is a list; @code{""}, if
@var{default} is @code{nil}; or @var{default}.  The string or strings
in @var{default} are also available to the user through the history
commands.

The function @code{completing-read} uses
@code{minibuffer-local-completion-map} as the keymap if
@var{require-match} is @code{nil}, and uses
@code{minibuffer-local-must-match-map} if @var{require-match} is
non-@code{nil}.  @xref{Completion Commands}.

The argument @var{history} specifies which history list variable to use for
saving the input and for minibuffer history commands.  It defaults to
@code{minibuffer-history}.  @xref{Minibuffer History}.

The argument @var{initial} is mostly deprecated; we recommend using a
non-@code{nil} value only in conjunction with specifying a cons cell
for @var{history}.  @xref{Initial Input}.  For default input, use
@var{default} instead.

If the argument @var{inherit-input-method} is non-@code{nil}, then the
minibuffer inherits the current input method (@pxref{Input
Methods}) and the setting of @code{enable-multibyte-characters}
(@pxref{Text Representations}) from whichever buffer was current before
entering the minibuffer.

If the variable @code{completion-ignore-case} is
non-@code{nil}, completion ignores case when comparing the input
against the possible matches.  @xref{Basic Completion}.  In this mode
of operation, @var{predicate} must also ignore case, or you will get
surprising results.

Here's an example of using @code{completing-read}:

@smallexample
@group
(completing-read
 "Complete a foo: "
 '(("foobar1" 1) ("barfoo" 2) ("foobaz" 3) ("foobar2" 4))
 nil t "fo")
@end group

@group
;; @r{After evaluation of the preceding expression,}
;;   @r{the following appears in the minibuffer:}

---------- Buffer: Minibuffer ----------
Complete a foo: fo@point{}
---------- Buffer: Minibuffer ----------
@end group
@end smallexample

@noindent
If the user then types @kbd{@key{DEL} @key{DEL} b @key{RET}},
@code{completing-read} returns @code{barfoo}.

The @code{completing-read} function binds variables to pass
information to the commands that actually do completion.
They are described in the following section.
@end defun

@defvar completing-read-function
The value of this variable must be a function, which is called by
@code{completing-read} to actually do its work.  It should accept the
same arguments as @code{completing-read}.  This can be bound to a
different function to completely override the normal behavior of
@code{completing-read}.
@end defvar

@node Completion Commands
@subsection Minibuffer Commands that Do Completion

  This section describes the keymaps, commands and user options used
in the minibuffer to do completion.

@defvar minibuffer-completion-table
The value of this variable is the completion table (@pxref{Basic
Completion}) used for completion in the minibuffer.  This is the
global variable that contains what @code{completing-read} passes to
@code{try-completion}.  It is used by minibuffer completion commands
such as @code{minibuffer-complete-word}.
@end defvar

@defvar minibuffer-completion-predicate
This variable's value is the predicate that @code{completing-read}
passes to @code{try-completion}.  The variable is also used by the other
minibuffer completion functions.
@end defvar

@defvar minibuffer-completion-confirm
This variable determines whether Emacs asks for confirmation before
exiting the minibuffer; @code{completing-read} binds this variable,
and the function @code{minibuffer-complete-and-exit} checks the value
before exiting.  If the value is @code{nil}, confirmation is not
required.  If the value is @code{confirm}, the user may exit with an
input that is not a valid completion alternative, but Emacs asks for
confirmation.  If the value is @code{confirm-after-completion}, the
user may exit with an input that is not a valid completion
alternative, but Emacs asks for confirmation if the user submitted the
input right after any of the completion commands in
@code{minibuffer-confirm-exit-commands}.
@end defvar

@defvar minibuffer-confirm-exit-commands
This variable holds a list of commands that cause Emacs to ask for
confirmation before exiting the minibuffer, if the @var{require-match}
argument to @code{completing-read} is @code{confirm-after-completion}.
The confirmation is requested if the user attempts to exit the
minibuffer immediately after calling any command in this list.
@end defvar

@deffn Command minibuffer-complete-word
This function completes the minibuffer contents by at most a single
word.  Even if the minibuffer contents have only one completion,
@code{minibuffer-complete-word} does not add any characters beyond the
first character that is not a word constituent.  @xref{Syntax Tables}.
@end deffn

@deffn Command minibuffer-complete
This function completes the minibuffer contents as far as possible.
@end deffn

@deffn Command minibuffer-complete-and-exit
This function completes the minibuffer contents, and exits if
confirmation is not required, i.e., if
@code{minibuffer-completion-confirm} is @code{nil}.  If confirmation
@emph{is} required, it is given by repeating this command
immediately---the command is programmed to work without confirmation
when run twice in succession.
@end deffn

@deffn Command minibuffer-completion-help
This function creates a list of the possible completions of the
current minibuffer contents.  It works by calling @code{all-completions}
using the value of the variable @code{minibuffer-completion-table} as
the @var{collection} argument, and the value of
@code{minibuffer-completion-predicate} as the @var{predicate} argument.
The list of completions is displayed as text in a buffer named
@file{*Completions*}.
@end deffn

@defun display-completion-list completions
This function displays @var{completions} to the stream in
@code{standard-output}, usually a buffer.  (@xref{Read and Print}, for more
information about streams.)  The argument @var{completions} is normally
a list of completions just returned by @code{all-completions}, but it
does not have to be.  Each element may be a symbol or a string, either
of which is simply printed.  It can also be a list of two strings,
which is printed as if the strings were concatenated.  The first of
the two strings is the actual completion, the second string serves as
annotation.

This function is called by @code{minibuffer-completion-help}.  A
common way to use it is together with
@code{with-output-to-temp-buffer}, like this:

@example
(with-output-to-temp-buffer "*Completions*"
  (display-completion-list
    (all-completions (buffer-string) my-alist)))
@end example
@end defun

@defopt completion-auto-help
If this variable is non-@code{nil}, the completion commands
automatically display a list of possible completions whenever nothing
can be completed because the next character is not uniquely determined.
@end defopt

@defvar minibuffer-local-completion-map
@code{completing-read} uses this value as the local keymap when an
exact match of one of the completions is not required.  By default, this
keymap makes the following bindings:

@table @asis
@item @kbd{?}
@code{minibuffer-completion-help}

@item @key{SPC}
@code{minibuffer-complete-word}

@item @key{TAB}
@code{minibuffer-complete}
@end table

@noindent
and uses @code{minibuffer-local-map} as its parent keymap
(@pxref{Definition of minibuffer-local-map}).
@end defvar

@defvar minibuffer-local-must-match-map
@code{completing-read} uses this value as the local keymap when an
exact match of one of the completions is required.  Therefore, no keys
are bound to @code{exit-minibuffer}, the command that exits the
minibuffer unconditionally.  By default, this keymap makes the following
bindings:

@table @asis
@item @kbd{C-j}
@code{minibuffer-complete-and-exit}

@item @key{RET}
@code{minibuffer-complete-and-exit}
@end table

@noindent
and uses @code{minibuffer-local-completion-map} as its parent keymap.
@end defvar

@defvar minibuffer-local-filename-completion-map
This is a sparse keymap that simply unbinds @key{SPC}; because
filenames can contain spaces.  The function @code{read-file-name}
combines this keymap with either @code{minibuffer-local-completion-map}
or @code{minibuffer-local-must-match-map}.
@end defvar

@defvar minibuffer-beginning-of-buffer-movement
If non-@code{nil}, the @kbd{M-<} command will move to the end of the
prompt if point is after the end of the prompt.  If point is at or
before the end of the prompt, move to the start of the buffer.  If
this variable is @code{nil}, the command behaves like
@code{beginning-of-buffer}.
@end defvar


@node High-Level Completion
@subsection High-Level Completion Functions

  This section describes the higher-level convenience functions for
reading certain sorts of names with completion.

  In most cases, you should not call these functions in the middle of a
Lisp function.  When possible, do all minibuffer input as part of
reading the arguments for a command, in the @code{interactive}
specification.  @xref{Defining Commands}.

@defun read-buffer prompt &optional default require-match predicate
This function reads the name of a buffer and returns it as a string.
It prompts with @var{prompt}.  The argument @var{default} is the
default name to use, the value to return if the user exits with an
empty minibuffer.  If non-@code{nil}, it should be a string, a list of
strings, or a buffer.  If it is a list, the default value is the first
element of this list.  It is mentioned in the prompt, but is not
inserted in the minibuffer as initial input.

The argument @var{prompt} should be a string ending with a colon and a
space.  If @var{default} is non-@code{nil}, the function inserts it in
@var{prompt} before the colon to follow the convention for reading from
the minibuffer with a default value (@pxref{Programming Tips}).

The optional argument @var{require-match} has the same meaning as in
@code{completing-read}.  @xref{Minibuffer Completion}.

The optional argument @var{predicate}, if non-@code{nil}, specifies a
function to filter the buffers that should be considered: the function
will be called with every potential candidate as its argument, and
should return @code{nil} to reject the candidate, non-@code{nil} to
accept it.

In the following example, the user enters @samp{minibuffer.t}, and
then types @key{RET}.  The argument @var{require-match} is @code{t},
and the only buffer name starting with the given input is
@samp{minibuffer.texi}, so that name is the value.

@example
(read-buffer "Buffer name: " "foo" t)
@group
;; @r{After evaluation of the preceding expression,}
;;   @r{the following prompt appears,}
;;   @r{with an empty minibuffer:}
@end group

@group
---------- Buffer: Minibuffer ----------
Buffer name (default foo): @point{}
---------- Buffer: Minibuffer ----------
@end group

@group
;; @r{The user types @kbd{minibuffer.t @key{RET}}.}
     @result{} "minibuffer.texi"
@end group
@end example
@end defun

@defopt read-buffer-function
This variable, if non-@code{nil}, specifies a function for reading
buffer names.  @code{read-buffer} calls this function instead of doing
its usual work, with the same arguments passed to @code{read-buffer}.
@end defopt

@defopt read-buffer-completion-ignore-case
If this variable is non-@code{nil}, @code{read-buffer} ignores case
when performing completion while reading the buffer name.
@end defopt

@defun read-command prompt &optional default
This function reads the name of a command and returns it as a Lisp
symbol.  The argument @var{prompt} is used as in
@code{read-from-minibuffer}.  Recall that a command is anything for
which @code{commandp} returns @code{t}, and a command name is a symbol
for which @code{commandp} returns @code{t}.  @xref{Interactive Call}.

The argument @var{default} specifies what to return if the user enters
null input.  It can be a symbol, a string or a list of strings.  If it
is a string, @code{read-command} interns it before returning it.
If it is a list, @code{read-command} interns the first element of this list.
If @var{default} is @code{nil}, that means no default has been
specified; then if the user enters null input, the return value is
@code{(intern "")}, that is, a symbol whose name is an empty string,
and whose printed representation is @code{##} (@pxref{Symbol Type}).

@example
(read-command "Command name? ")

@group
;; @r{After evaluation of the preceding expression,}
;;   @r{the following prompt appears with an empty minibuffer:}
@end group

@group
---------- Buffer: Minibuffer ----------
Command name?
---------- Buffer: Minibuffer ----------
@end group
@end example

@noindent
If the user types @kbd{forward-c @key{RET}}, then this function returns
@code{forward-char}.

The @code{read-command} function is a simplified interface to
@code{completing-read}.  It uses the variable @code{obarray} so as to
complete in the set of extant Lisp symbols, and it uses the
@code{commandp} predicate so as to accept only command names:

@cindex @code{commandp} example
@example
@group
(read-command @var{prompt})
@equiv{}
(intern (completing-read @var{prompt} obarray
                         'commandp t nil))
@end group
@end example
@end defun

@defun read-variable prompt &optional default
@anchor{Definition of read-variable}
This function reads the name of a customizable variable and returns it
as a symbol.  Its arguments have the same form as those of
@code{read-command}.  It behaves just like @code{read-command}, except
that it uses the predicate @code{custom-variable-p} instead of
@code{commandp}.
@end defun

@deffn Command read-color &optional prompt convert allow-empty display
This function reads a string that is a color specification, either the
color's name or an RGB hex value such as @code{#RRRGGGBBB}.  It
prompts with @var{prompt} (default: @code{"Color (name or #RGB triplet):"})
and provides completion for color names, but not for hex RGB values.
In addition to names of standard colors, completion candidates include
the foreground and background colors at point.

Valid RGB values are described in @ref{Color Names}.

The function's return value is the string typed by the user in the
minibuffer.  However, when called interactively or if the optional
argument @var{convert} is non-@code{nil}, it converts any input color
name into the corresponding RGB value string and instead returns that.
This function requires a valid color specification to be input.
Empty color names are allowed when @var{allow-empty} is
non-@code{nil} and the user enters null input.

Interactively, or when @var{display} is non-@code{nil}, the return
value is also displayed in the echo area.
@end deffn

  See also the functions @code{read-coding-system} and
@code{read-non-nil-coding-system}, in @ref{User-Chosen Coding Systems},
and @code{read-input-method-name}, in @ref{Input Methods}.

@node Reading File Names
@subsection Reading File Names
@cindex read file names
@cindex prompt for file name

  The high-level completion functions @code{read-file-name},
@code{read-directory-name}, and @code{read-shell-command} are designed
to read file names, directory names, and shell commands, respectively.
They provide special features, including automatic insertion of the
default directory.

@defun read-file-name prompt &optional directory default require-match initial predicate
This function reads a file name, prompting with @var{prompt} and
providing completion.

As an exception, this function reads a file name using a graphical
file dialog instead of the minibuffer, if all of the following are
true:

@enumerate
@item
It is invoked via a mouse command.

@item
The selected frame is on a graphical display supporting such dialogs.

@item
The variable @code{use-dialog-box} is non-@code{nil}.
@xref{Dialog Boxes,, Dialog Boxes, emacs, The GNU Emacs Manual}.

@item
The @var{directory} argument, described below, does not specify a
remote file.  @xref{Remote Files,, Remote Files, emacs, The GNU Emacs Manual}.
@end enumerate

@noindent
The exact behavior when using a graphical file dialog is
platform-dependent.  Here, we simply document the behavior when using
the minibuffer.

@code{read-file-name} does not automatically expand the returned file
name.  You can call @code{expand-file-name} yourself if an absolute
file name is required.

The optional argument @var{require-match} has the same meaning as in
@code{completing-read}.  @xref{Minibuffer Completion}.

The argument @var{directory} specifies the directory to use for
completing relative file names.  It should be an absolute directory
name.  If the variable @code{insert-default-directory} is non-@code{nil},
@var{directory} is also inserted in the minibuffer as initial input.
It defaults to the current buffer's value of @code{default-directory}.

If you specify @var{initial}, that is an initial file name to insert
in the buffer (after @var{directory}, if that is inserted).  In this
case, point goes at the beginning of @var{initial}.  The default for
@var{initial} is @code{nil}---don't insert any file name.  To see what
@var{initial} does, try the command @kbd{C-x C-v} in a buffer visiting
a file.  @strong{Please note:} we recommend using @var{default} rather
than @var{initial} in most cases.

If @var{default} is non-@code{nil}, then the function returns
@var{default} if the user exits the minibuffer with the same non-empty
contents that @code{read-file-name} inserted initially.  The initial
minibuffer contents are always non-empty if
@code{insert-default-directory} is non-@code{nil}, as it is by
default.  @var{default} is not checked for validity, regardless of the
value of @var{require-match}.  However, if @var{require-match} is
non-@code{nil}, the initial minibuffer contents should be a valid file
(or directory) name.  Otherwise @code{read-file-name} attempts
completion if the user exits without any editing, and does not return
@var{default}.  @var{default} is also available through the history
commands.

If @var{default} is @code{nil}, @code{read-file-name} tries to find a
substitute default to use in its place, which it treats in exactly the
same way as if it had been specified explicitly.  If @var{default} is
@code{nil}, but @var{initial} is non-@code{nil}, then the default is
the absolute file name obtained from @var{directory} and
@var{initial}.  If both @var{default} and @var{initial} are @code{nil}
and the buffer is visiting a file, @code{read-file-name} uses the
absolute file name of that file as default.  If the buffer is not
visiting a file, then there is no default.  In that case, if the user
types @key{RET} without any editing, @code{read-file-name} simply
returns the pre-inserted contents of the minibuffer.

If the user types @key{RET} in an empty minibuffer, this function
returns an empty string, regardless of the value of
@var{require-match}.  This is, for instance, how the user can make the
current buffer visit no file using @kbd{M-x set-visited-file-name}.

If @var{predicate} is non-@code{nil}, it specifies a function of one
argument that decides which file names are acceptable completion
alternatives.  A file name is an acceptable value if @var{predicate}
returns non-@code{nil} for it.

Here is an example of using @code{read-file-name}:

@example
@group
(read-file-name "The file is ")

;; @r{After evaluation of the preceding expression,}
;;   @r{the following appears in the minibuffer:}
@end group

@group
---------- Buffer: Minibuffer ----------
The file is /gp/gnu/elisp/@point{}
---------- Buffer: Minibuffer ----------
@end group
@end example

@noindent
Typing @kbd{manual @key{TAB}} results in the following:

@example
@group
---------- Buffer: Minibuffer ----------
The file is /gp/gnu/elisp/manual.texi@point{}
---------- Buffer: Minibuffer ----------
@end group
@end example

@c Wordy to avoid overfull hbox in smallbook mode.
@noindent
If the user types @key{RET}, @code{read-file-name} returns the file name
as the string @code{"/gp/gnu/elisp/manual.texi"}.
@end defun

@defvar read-file-name-function
If non-@code{nil}, this should be a function that accepts the same
arguments as @code{read-file-name}.  When @code{read-file-name} is
called, it calls this function with the supplied arguments instead of
doing its usual work.
@end defvar

@defopt read-file-name-completion-ignore-case
If this variable is non-@code{nil}, @code{read-file-name} ignores case
when performing completion.
@end defopt

@defun read-directory-name prompt &optional directory default require-match initial
This function is like @code{read-file-name} but allows only directory
names as completion alternatives.

If @var{default} is @code{nil} and @var{initial} is non-@code{nil},
@code{read-directory-name} constructs a substitute default by
combining @var{directory} (or the current buffer's default directory
if @var{directory} is @code{nil}) and @var{initial}.  If both
@var{default} and @var{initial} are @code{nil}, this function uses
@var{directory} as substitute default, or the current buffer's default
directory if @var{directory} is @code{nil}.
@end defun

@defopt insert-default-directory
This variable is used by @code{read-file-name}, and thus, indirectly,
by most commands reading file names.  (This includes all commands that
use the code letters @samp{f} or @samp{F} in their interactive form.
@xref{Interactive Codes,, Code Characters for interactive}.)  Its
value controls whether @code{read-file-name} starts by placing the
name of the default directory in the minibuffer, plus the initial file
name, if any.  If the value of this variable is @code{nil}, then
@code{read-file-name} does not place any initial input in the
minibuffer (unless you specify initial input with the @var{initial}
argument).  In that case, the default directory is still used for
completion of relative file names, but is not displayed.

If this variable is @code{nil} and the initial minibuffer contents are
empty, the user may have to explicitly fetch the next history element
to access a default value.  If the variable is non-@code{nil}, the
initial minibuffer contents are always non-empty and the user can
always request a default value by immediately typing @key{RET} in an
unedited minibuffer.  (See above.)

For example:

@example
@group
;; @r{Here the minibuffer starts out with the default directory.}
(let ((insert-default-directory t))
  (read-file-name "The file is "))
@end group

@group
---------- Buffer: Minibuffer ----------
The file is ~lewis/manual/@point{}
---------- Buffer: Minibuffer ----------
@end group

@group
;; @r{Here the minibuffer is empty and only the prompt}
;;   @r{appears on its line.}
(let ((insert-default-directory nil))
  (read-file-name "The file is "))
@end group

@group
---------- Buffer: Minibuffer ----------
The file is @point{}
---------- Buffer: Minibuffer ----------
@end group
@end example
@end defopt

@defun read-shell-command prompt &optional initial history &rest args
This function reads a shell command from the minibuffer, prompting
with @var{prompt} and providing intelligent completion.  It completes
the first word of the command using candidates that are appropriate
for command names, and the rest of the command words as file names.

This function uses @code{minibuffer-local-shell-command-map} as the
keymap for minibuffer input.  The @var{history} argument specifies the
history list to use; if is omitted or @code{nil}, it defaults to
@code{shell-command-history} (@pxref{Minibuffer History,
shell-command-history}).  The optional argument @var{initial}
specifies the initial content of the minibuffer (@pxref{Initial
Input}).  The rest of @var{args}, if present, are used as the
@var{default} and @var{inherit-input-method} arguments in
@code{read-from-minibuffer} (@pxref{Text from Minibuffer}).
@end defun

@defvar minibuffer-local-shell-command-map
This keymap is used by @code{read-shell-command} for completing
command and file names that are part of a shell command.  It uses
@code{minibuffer-local-map} as its parent keymap, and binds @key{TAB}
to @code{completion-at-point}.
@end defvar

@node Completion Variables
@subsection Completion Variables

  Here are some variables that can be used to alter the default
completion behavior.

@cindex completion styles
@defopt completion-styles
The value of this variable is a list of completion style (symbols) to
use for performing completion.  A @dfn{completion style} is a set of
rules for generating completions.  Each symbol occurring this list
must have a corresponding entry in @code{completion-styles-alist}.
@end defopt

@defvar completion-styles-alist
This variable stores a list of available completion styles.  Each
element in the list has the form

@example
(@var{style} @var{try-completion} @var{all-completions} @var{doc})
@end example

@noindent
Here, @var{style} is the name of the completion style (a symbol),
which may be used in the @code{completion-styles} variable to refer to
this style; @var{try-completion} is the function that does the
completion; @var{all-completions} is the function that lists the
completions; and @var{doc} is a string describing the completion
style.

The @var{try-completion} and @var{all-completions} functions should
each accept four arguments: @var{string}, @var{collection},
@var{predicate}, and @var{point}.  The @var{string}, @var{collection},
and @var{predicate} arguments have the same meanings as in
@code{try-completion} (@pxref{Basic Completion}), and the @var{point}
argument is the position of point within @var{string}.  Each function
should return a non-@code{nil} value if it performed its job, and
@code{nil} if it did not (e.g., if there is no way to complete
@var{string} according to the completion style).

When the user calls a completion command like
@code{minibuffer-complete} (@pxref{Completion Commands}), Emacs looks
for the first style listed in @code{completion-styles} and calls its
@var{try-completion} function.  If this function returns @code{nil},
Emacs moves to the next listed completion style and calls its
@var{try-completion} function, and so on until one of the
@var{try-completion} functions successfully performs completion and
returns a non-@code{nil} value.  A similar procedure is used for
listing completions, via the @var{all-completions} functions.

@xref{Completion Styles,,, emacs, The GNU Emacs Manual}, for a
description of the available completion styles.
@end defvar

@defopt completion-category-overrides
This variable specifies special completion styles and other completion
behaviors to use when completing certain types of text.  Its value
should be an alist with elements of the form @code{(@var{category}
. @var{alist})}.  @var{category} is a symbol describing what is being
completed; currently, the @code{buffer}, @code{file}, and
@code{unicode-name} categories are defined, but others can be defined
via specialized completion functions (@pxref{Programmed Completion}).
@var{alist} is an association list describing how completion should
behave for the corresponding category.  The following alist keys are
supported:

@table @code
@item styles
The value should be a list of completion styles (symbols).

@item cycle
The value should be a value for @code{completion-cycle-threshold}
(@pxref{Completion Options,,, emacs, The GNU Emacs Manual}) for this
category.
@end table

@noindent
Additional alist entries may be defined in the future.
@end defopt

@defvar completion-extra-properties
This variable is used to specify extra properties of the current
completion command.  It is intended to be let-bound by specialized
completion commands.  Its value should be a list of property and value
pairs.  The following properties are supported:

@table @code
@item :annotation-function
The value should be a function to add annotations in the completions
buffer.  This function must accept one argument, a completion, and
should either return @code{nil} or a string to be displayed next to
the completion.  Unless this function puts own face on the annotation
suffix string, the @code{completions-annotations} face is added by
default to that string.

@item :affixation-function
The value should be a function to add prefixes and suffixes to
completions.  This function must accept one argument, a list of
completions, and should return such a list of completions where
each element contains a list of three elements: a completion,
a prefix string, and a suffix string.  When this function
returns a list of two elements, it is interpreted as a list
of a completion and a suffix string like in @code{:annotation-function}.
This function takes priority over @code{:annotation-function}.

@item :exit-function
The value should be a function to run after performing completion.
The function should accept two arguments, @var{string} and
@var{status}, where @var{string} is the text to which the field was
completed, and @var{status} indicates what kind of operation happened:
@code{finished} if text is now complete, @code{sole} if the text
cannot be further completed but completion is not finished, or
@code{exact} if the text is a valid completion but may be further
completed.
@end table
@end defvar

@node Programmed Completion
@subsection Programmed Completion
@cindex programmed completion

  Sometimes it is not possible or convenient to create an alist or
an obarray containing all the intended possible completions ahead
of time.  In such a case, you can supply your own function to compute
the completion of a given string.  This is called @dfn{programmed
completion}.  Emacs uses programmed completion when completing file
names (@pxref{File Name Completion}), among many other cases.

  To use this feature, pass a function as the @var{collection}
argument to @code{completing-read}.  The function
@code{completing-read} arranges to pass your completion function along
to @code{try-completion}, @code{all-completions}, and other basic
completion functions, which will then let your function do all
the work.

  The completion function should accept three arguments:

@itemize @bullet
@item
The string to be completed.

@item
A predicate function with which to filter possible matches, or
@code{nil} if none.  The function should call the predicate for each
possible match, and ignore the match if the predicate returns
@code{nil}.

@item
A flag specifying the type of completion operation to perform; see
@ref{Basic Completion}, for the details of those operations.  This
flag may be one of the following values.

@table @code
@item nil
This specifies a @code{try-completion} operation.  The function should
return @code{nil} if there are no matches; it should return @code{t}
if the specified string is a unique and exact match; and it should
return the longest common prefix substring of all matches otherwise.

@item t
This specifies an @code{all-completions} operation.  The function
should return a list of all possible completions of the specified
string.

@item lambda
This specifies a @code{test-completion} operation.  The function
should return @code{t} if the specified string is an exact match for
some completion alternative; @code{nil} otherwise.

@item (boundaries . @var{suffix})
This specifies a @code{completion-boundaries} operation.  The function
should return @code{(boundaries @var{start} . @var{end})}, where
@var{start} is the position of the beginning boundary in the specified
string, and @var{end} is the position of the end boundary in
@var{suffix}.

@item metadata
This specifies a request for information about the state of the
current completion.  The return value should have the form
@code{(metadata . @var{alist})}, where @var{alist} is an alist whose
elements are described below.
@end table

@noindent
If the flag has any other value, the completion function should return
@code{nil}.
@end itemize

The following is a list of metadata entries that a completion function
may return in response to a @code{metadata} flag argument:

@table @code
@item category
The value should be a symbol describing what kind of text the
completion function is trying to complete.  If the symbol matches one
of the keys in @code{completion-category-overrides}, the usual
completion behavior is overridden.  @xref{Completion Variables}.

@item annotation-function
The value should be a function for @dfn{annotating} completions.  The
function should take one argument, @var{string}, which is a possible
completion.  It should return a string, which is displayed after the
completion @var{string} in the @file{*Completions*} buffer.
Unless this function puts own face on the annotation suffix string,
the @code{completions-annotations} face is added by default to
that string.

@item affixation-function
The value should be a function for adding prefixes and suffixes to
completions.  The function should take one argument,
@var{completions}, which is a list of possible completions.  It should
return such a list of @var{completions} where each element contains a list
of three elements: a completion, a prefix which is displayed before
the completion string in the @file{*Completions*} buffer, and
a suffix displayed after the completion string.  When this function
returns a list of two elements, it is interpreted as a list of
a completion and a suffix string like in @code{annotation-function}.
This function takes priority over @code{annotation-function}.

@item display-sort-function
The value should be a function for sorting completions.  The function
should take one argument, a list of completion strings, and return a
sorted list of completion strings.  It is allowed to alter the input
list destructively.

@item cycle-sort-function
The value should be a function for sorting completions, when
@code{completion-cycle-threshold} is non-@code{nil} and the user is
cycling through completion alternatives.  @xref{Completion Options,,,
emacs, The GNU Emacs Manual}.  Its argument list and return value are
the same as for @code{display-sort-function}.
@end table

@defun completion-table-dynamic function &optional switch-buffer
This function is a convenient way to write a function that can act as
a programmed completion function.  The argument @var{function} should
be a function that takes one argument, a string, and returns a
completion table (@pxref{Basic Completion}) containing all the
possible completions.  The table returned by @var{function} can also
include elements that don't match the string argument; they are
automatically filtered out by @code{completion-table-dynamic}.  In
particular, @var{function} can ignore its argument and return a full
list of all possible completions.  You can think of
@code{completion-table-dynamic} as a transducer between @var{function}
and the interface for programmed completion functions.

If the optional argument @var{switch-buffer} is non-@code{nil}, and
completion is performed in the minibuffer, @var{function} will be
called with current buffer set to the buffer from which the minibuffer
was entered.

The return value of @code{completion-table-dynamic} is a function that
can be used as the 2nd argument to @code{try-completion} and
@code{all-completions}.  Note that this function will always return
empty metadata and trivial boundaries (@pxref{Programmed Completion}).
@end defun

@defun completion-table-with-cache function &optional ignore-case
This is a wrapper for @code{completion-table-dynamic} that saves the
last argument-result pair.  This means that multiple lookups with the
same argument only need to call @var{function} once.  This can be useful
when a slow operation is involved, such as calling an external process.
@end defun

@node Completion in Buffers
@subsection Completion in Ordinary Buffers
@cindex inline completion

@findex completion-at-point
  Although completion is usually done in the minibuffer, the
completion facility can also be used on the text in ordinary Emacs
buffers.  In many major modes, in-buffer completion is performed by
the @kbd{C-M-i} or @kbd{M-@key{TAB}} command, bound to
@code{completion-at-point}.  @xref{Symbol Completion,,, emacs, The GNU
Emacs Manual}.  This command uses the abnormal hook variable
@code{completion-at-point-functions}:

@defvar completion-at-point-functions
The value of this abnormal hook should be a list of functions, which
are used to compute a completion table (@pxref{Basic Completion}) for
completing the text at point.  It can be used by major modes to
provide mode-specific completion tables (@pxref{Major Mode
Conventions}).

When the command @code{completion-at-point} runs, it calls the
functions in the list one by one, without any argument.  Each function
should return @code{nil} unless it can and wants to take
responsibility for the completion data for the text at point.
Otherwise it should return a list of the following form:

@example
(@var{start} @var{end} @var{collection} . @var{props})
@end example

@noindent
@var{start} and @var{end} delimit the text to complete (which should
enclose point).  @var{collection} is a completion table for completing
that text, in a form suitable for passing as the second argument to
@code{try-completion} (@pxref{Basic Completion}); completion
alternatives will be generated from this completion table in the usual
way, via the completion styles defined in @code{completion-styles}
(@pxref{Completion Variables}).  @var{props} is a property list for
additional information; any of the properties in
@code{completion-extra-properties} are recognized (@pxref{Completion
Variables}), as well as the following additional ones:

@table @code
@item :predicate
The value should be a predicate that completion candidates need to
satisfy.

@item :exclusive
If the value is @code{no}, then if the completion table fails to match
the text at point, @code{completion-at-point} moves on to the
next function in @code{completion-at-point-functions} instead of
reporting a completion failure.
@end table

The functions on this hook should generally return quickly, since they
may be called very often (e.g., from @code{post-command-hook}).
Supplying a function for @var{collection} is strongly recommended if
generating the list of completions is an expensive operation.  Emacs
may internally call functions in @code{completion-at-point-functions}
many times, but care about the value of @var{collection} for only some
of these calls.  By supplying a function for @var{collection}, Emacs
can defer generating completions until necessary.  You can use
@code{completion-table-dynamic} to create a wrapper function:

@smallexample
;; Avoid this pattern.
(let ((beg ...) (end ...) (my-completions (my-make-completions)))
  (list beg end my-completions))

;; Use this instead.
(let ((beg ...) (end ...))
  (list beg
        end
        (completion-table-dynamic
          (lambda (_)
            (my-make-completions)))))
@end smallexample

Additionally, the @var{collection} should generally not be
pre-filtered based on the current text between @var{start} and
@var{end}, because that is the responsibility of the caller of
@code{completion-at-point-functions} to do that according to the
completion styles it decides to use.

A function in @code{completion-at-point-functions} may also return a
function instead of a list as described above.  In that case, that
returned function is called, with no argument, and it is entirely
responsible for performing the completion.  We discourage this usage;
it is only intended to help convert old code to using
@code{completion-at-point}.

The first function in @code{completion-at-point-functions} to return a
non-@code{nil} value is used by @code{completion-at-point}.  The
remaining functions are not called.  The exception to this is when
there is an @code{:exclusive} specification, as described above.
@end defvar

  The following function provides a convenient way to perform
completion on an arbitrary stretch of text in an Emacs buffer:

@defun completion-in-region start end collection &optional predicate
This function completes the text in the current buffer between the
positions @var{start} and @var{end}, using @var{collection}.  The
argument @var{collection} has the same meaning as in
@code{try-completion} (@pxref{Basic Completion}).

This function inserts the completion text directly into the current
buffer.  Unlike @code{completing-read} (@pxref{Minibuffer
Completion}), it does not activate the minibuffer.

For this function to work, point must be somewhere between @var{start}
and @var{end}.
@end defun


@node Yes-or-No Queries
@section Yes-or-No Queries
@cindex asking the user questions
@cindex querying the user
@cindex yes-or-no questions

  This section describes functions used to ask the user a yes-or-no
question.  The function @code{y-or-n-p} can be answered with a single
character; it is useful for questions where an inadvertent wrong answer
will not have serious consequences.  @code{yes-or-no-p} is suitable for
more momentous questions, since it requires three or four characters to
answer.

   If either of these functions is called in a command that was invoked
using the mouse---more precisely, if @code{last-nonmenu-event}
(@pxref{Command Loop Info}) is either @code{nil} or a list---then it
uses a dialog box or pop-up menu to ask the question.  Otherwise, it
uses keyboard input.  You can force use either of the mouse or of keyboard
input by binding @code{last-nonmenu-event} to a suitable value around
the call.

  Both @code{yes-or-no-p} and @code{y-or-n-p} use the minibuffer.

@defun y-or-n-p prompt
This function asks the user a question, expecting input in the minibuffer.
It returns @code{t} if the user types @kbd{y}, @code{nil} if the user
types @kbd{n}.  This function also accepts @key{SPC} to mean yes and
@key{DEL} to mean no.  It accepts @kbd{C-]} and @kbd{C-g} to quit,
because the question uses the minibuffer and for that reason the user
might try to use @kbd{C-]} to get out.  The answer is a single
character, with no @key{RET} needed to terminate it.  Upper and lower
case are equivalent.

``Asking the question'' means printing @var{prompt} in the minibuffer,
followed by the string @w{@samp{(y or n) }}.  If the input is not one of
the expected answers (@kbd{y}, @kbd{n}, @kbd{@key{SPC}},
@kbd{@key{DEL}}, or something that quits), the function responds
@samp{Please answer y or n.}, and repeats the request.

This function actually uses the minibuffer, but does not allow editing
of the answer.  The cursor moves to the minibuffer while the question
is being asked.

The answers and their meanings, even @samp{y} and @samp{n}, are not
hardwired, and are specified by the keymap @code{query-replace-map}
(@pxref{Search and Replace}).  In particular, if the user enters the
special responses @code{recenter}, @code{scroll-up},
@code{scroll-down}, @code{scroll-other-window}, or
@code{scroll-other-window-down} (respectively bound to @kbd{C-l},
@kbd{C-v}, @kbd{M-v}, @kbd{C-M-v} and @kbd{C-M-S-v} in
@code{query-replace-map}), this function performs the specified window
recentering or scrolling operation, and poses the question again.

If you bind @code{help-form} (@pxref{Help Functions}) to
a non-@code{nil} value while calling @code{y-or-n-p}, then pressing
@code{help-char} causes it to evaluate @code{help-form} and display
the result.  @code{help-char} is automatically added to @var{prompt}.
@end defun

@defun y-or-n-p-with-timeout prompt seconds default
Like @code{y-or-n-p}, except that if the user fails to answer within
@var{seconds} seconds, this function stops waiting and returns
@var{default}.  It works by setting up a timer; see @ref{Timers}.
The argument @var{seconds} should be a number.
@end defun

@defun yes-or-no-p prompt
This function asks the user a question, expecting input in the
minibuffer.  It returns @code{t} if the user enters @samp{yes},
@code{nil} if the user types @samp{no}.  The user must type @key{RET} to
finalize the response.  Upper and lower case are equivalent.

@code{yes-or-no-p} starts by displaying @var{prompt} in the minibuffer,
followed by @w{@samp{(yes or no) }}.  The user must type one of the
expected responses; otherwise, the function responds @samp{Please answer
yes or no.}, waits about two seconds and repeats the request.

@code{yes-or-no-p} requires more work from the user than
@code{y-or-n-p} and is appropriate for more crucial decisions.

Here is an example:

@smallexample
@group
(yes-or-no-p "Do you really want to remove everything? ")

;; @r{After evaluation of the preceding expression,}
;;   @r{the following prompt appears,}
;;   @r{with an empty minibuffer:}
@end group

@group
---------- Buffer: minibuffer ----------
Do you really want to remove everything? (yes or no)
---------- Buffer: minibuffer ----------
@end group
@end smallexample

@noindent
If the user first types @kbd{y @key{RET}}, which is invalid because this
function demands the entire word @samp{yes}, it responds by displaying
these prompts, with a brief pause between them:

@smallexample
@group
---------- Buffer: minibuffer ----------
Please answer yes or no.
Do you really want to remove everything? (yes or no)
---------- Buffer: minibuffer ----------
@end group
@end smallexample
@end defun

@node Multiple Queries
@section Asking Multiple-Choice Questions

  This section describes facilities for asking the user more complex
questions or several similar questions.

@cindex multiple yes-or-no questions
  When you have a series of similar questions to ask, such as ``Do you
want to save this buffer?'' for each buffer in turn, you should use
@code{map-y-or-n-p} to ask the collection of questions, rather than
asking each question individually.  This gives the user certain
convenient facilities such as the ability to answer the whole series at
once.

@defun map-y-or-n-p prompter actor list &optional help action-alist no-cursor-in-echo-area
This function asks the user a series of questions, reading a
single-character answer in the echo area for each one.

The value of @var{list} specifies the objects to ask questions about.
It should be either a list of objects or a generator function.  If it is
a function, it should expect no arguments, and should return either the
next object to ask about, or @code{nil}, meaning to stop asking questions.

The argument @var{prompter} specifies how to ask each question.  If
@var{prompter} is a string, the question text is computed like this:

@example
(format @var{prompter} @var{object})
@end example

@noindent
where @var{object} is the next object to ask about (as obtained from
@var{list}).

If not a string, @var{prompter} should be a function of one argument
(the next object to ask about) and should return the question text.  If
the value is a string, that is the question to ask the user.  The
function can also return @code{t}, meaning do act on this object (and
don't ask the user), or @code{nil}, meaning ignore this object (and don't
ask the user).

The argument @var{actor} says how to act on the answers that the user
gives.  It should be a function of one argument, and it is called with
each object that the user says yes for.  Its argument is always an
object obtained from @var{list}.

If the argument @var{help} is given, it should be a list of this form:

@example
(@var{singular} @var{plural} @var{action})
@end example

@noindent
where @var{singular} is a string containing a singular noun that
describes the objects conceptually being acted on, @var{plural} is the
corresponding plural noun, and @var{action} is a transitive verb
describing what @var{actor} does.

If you don't specify @var{help}, the default is @code{("object"
"objects" "act on")}.

Each time a question is asked, the user may enter @kbd{y}, @kbd{Y}, or
@key{SPC} to act on that object; @kbd{n}, @kbd{N}, or @key{DEL} to skip
that object; @kbd{!} to act on all following objects; @key{ESC} or
@kbd{q} to exit (skip all following objects); @kbd{.} (period) to act on
the current object and then exit; or @kbd{C-h} to get help.  These are
the same answers that @code{query-replace} accepts.  The keymap
@code{query-replace-map} defines their meaning for @code{map-y-or-n-p}
as well as for @code{query-replace}; see @ref{Search and Replace}.

You can use @var{action-alist} to specify additional possible answers
and what they mean.  It is an alist of elements of the form
@code{(@var{char} @var{function} @var{help})}, each of which defines one
additional answer.  In this element, @var{char} is a character (the
answer); @var{function} is a function of one argument (an object from
@var{list}); @var{help} is a string.

When the user responds with @var{char}, @code{map-y-or-n-p} calls
@var{function}.  If it returns non-@code{nil}, the object is considered
acted upon, and @code{map-y-or-n-p} advances to the next object in
@var{list}.  If it returns @code{nil}, the prompt is repeated for the
same object.

Normally, @code{map-y-or-n-p} binds @code{cursor-in-echo-area} while
prompting.  But if @var{no-cursor-in-echo-area} is non-@code{nil}, it
does not do that.

If @code{map-y-or-n-p} is called in a command that was invoked using the
mouse---more precisely, if @code{last-nonmenu-event} (@pxref{Command
Loop Info}) is either @code{nil} or a list---then it uses a dialog box
or pop-up menu to ask the question.  In this case, it does not use
keyboard input or the echo area.  You can force use either of the mouse or
of keyboard input by binding @code{last-nonmenu-event} to a suitable
value around the call.

The return value of @code{map-y-or-n-p} is the number of objects acted on.
@end defun
@c FIXME  An example of this would be more useful than all the
@c preceding examples of simple things.

If you need to ask the user a question that might have more than just
2 answers, use @code{read-answer}.

@defun read-answer question answers
@vindex read-answer-short
This function prompts the user with text in @var{question}, which
should end in the @samp{SPC} character.  The function includes in the
prompt the possible responses in @var{answers} by appending them to
the end of @var{question}.  The possible responses are provided in
@var{answers} as an alist whose elements are of the following form:

@lisp
(@var{long-answer} @var{short-answer} @var{help-message})
@end lisp

@noindent
where @var{long-answer} is the complete text of the user response, a
string; @var{short-answer} is a short form of the same response, a
single character or a function key; and @var{help-message} is the text
that describes the meaning of the answer.  If the variable
@code{read-answer-short} is non-@code{nil}, the prompt will show the
short variants of the possible answers and the user is expected to
type the single characters/keys shown in the prompt; otherwise the
prompt will show the long variants of the answers, and the user is
expected to type the full text of one of the answers and end by
pressing @key{RET}.  If @code{use-dialog-box} is non-@code{nil}, and
this function was invoked by mouse events, the question and the
answers will be displayed in a GUI dialog box.

The function returns the text of the @var{long-answer} selected by the
user, regardless of whether long or short answers were shown in the
prompt and typed by the user.

Here is an example of using this function:

@lisp
(let ((read-answer-short t))
  (read-answer "Foo "
     '(("yes"  ?y "perform the action")
       ("no"   ?n "skip to the next")
       ("all"  ?! "perform for the rest without more questions")
       ("help" ?h "show help")
       ("quit" ?q "exit"))))
@end lisp
@end defun

@defun read-char-from-minibuffer prompt &optional chars history
This function uses the minibuffer to read and return a single
character.  Optionally, it ignores any input that is not a member of
@var{chars}, a list of accepted characters.  The @var{history}
argument specifies the history list symbol to use; if it is omitted or
@code{nil}, this function doesn't use the history.

If you bind @code{help-form} (@pxref{Help Functions}) to
a non-@code{nil} value while calling @code{read-char-from-minibuffer},
then pressing @code{help-char} causes it to evaluate @code{help-form}
and display the result.
@end defun

@node Reading a Password
@section Reading a Password
@cindex passwords, reading

  To read a password to pass to another program, you can use the
function @code{read-passwd}.

@vindex read-hide-char
@defun read-passwd prompt &optional confirm default
This function reads a password, prompting with @var{prompt}.  It does
not echo the password as the user types it; instead, it echoes
@samp{*}  for each character in the password.  If you want to apply
another character to hide the password, let-bind the variable
@code{read-hide-char} with that character.

The optional argument @var{confirm}, if non-@code{nil}, says to read the
password twice and insist it must be the same both times.  If it isn't
the same, the user has to type it over and over until the last two
times match.

The optional argument @var{default} specifies the default password to
return if the user enters empty input.  If @var{default} is @code{nil},
then @code{read-passwd} returns the null string in that case.
@end defun

@node Minibuffer Commands
@section Minibuffer Commands

  This section describes some commands meant for use in the
minibuffer.

@deffn Command exit-minibuffer
This command exits the active minibuffer.  It is normally bound to
keys in minibuffer local keymaps.  The command throws an error if the
current buffer is not the active minibuffer.
@end deffn

@deffn Command self-insert-and-exit
This command exits the active minibuffer after inserting the last
character typed on the keyboard (found in @code{last-command-event};
@pxref{Command Loop Info}).
@end deffn

@deffn Command previous-history-element n
This command replaces the minibuffer contents with the value of the
@var{n}th previous (older) history element.
@end deffn

@deffn Command next-history-element n
This command replaces the minibuffer contents with the value of the
@var{n}th more recent history element.  The position in the history
can go beyond the current position and invoke ``future history''
(@pxref{Text from Minibuffer}).
@end deffn

@deffn Command previous-matching-history-element pattern n
This command replaces the minibuffer contents with the value of the
@var{n}th previous (older) history element that matches @var{pattern} (a
regular expression).
@end deffn

@deffn Command next-matching-history-element pattern n
This command replaces the minibuffer contents with the value of the
@var{n}th next (newer) history element that matches @var{pattern} (a
regular expression).
@end deffn

@deffn Command previous-complete-history-element n
This command replaces the minibuffer contents with the value of the
@var{n}th previous (older) history element that completes the current
contents of the minibuffer before the point.
@end deffn

@deffn Command next-complete-history-element n
This command replaces the minibuffer contents with the value of the
@var{n}th next (newer) history element that completes the current
contents of the minibuffer before the point.
@end deffn

@deffn Command goto-history-element nabs
This function puts element of the minibuffer history in the
minibuffer.  The argument @var{nabs} specifies the absolute history
position in descending order, where 0 means the current element and a
positive number @var{n} means the @var{n}th previous element.  NABS
being a negative number -@var{n} means the @var{n}th entry of ``future
history.''
@end deffn

@node Minibuffer Windows
@section Minibuffer Windows
@cindex minibuffer windows

These functions access and select minibuffer windows, test whether they
are active and control how they get resized.

@defun minibuffer-window &optional frame
@anchor{Definition of minibuffer-window}
This function returns the minibuffer window used for frame @var{frame}.
If @var{frame} is @code{nil}, that stands for the selected frame.

Note that the minibuffer window used by a frame need not be part of that
frame---a frame that has no minibuffer of its own necessarily uses some
other frame's minibuffer window.  The minibuffer window of a
minibuffer-less frame can be changed by setting that frame's
@code{minibuffer} frame parameter (@pxref{Buffer Parameters}).
@end defun

@defun set-minibuffer-window window
This function specifies @var{window} as the minibuffer window to use.
This affects where the minibuffer is displayed if you put text in it
without invoking the usual minibuffer commands.  It has no effect on the
usual minibuffer input functions because they all start by choosing the
minibuffer window according to the selected frame.
@end defun

@c Emacs 19 feature
@defun window-minibuffer-p &optional window
This function returns @code{t} if @var{window} is a minibuffer window.
@var{window} defaults to the selected window.
@end defun

The following function returns the window showing the currently active
minibuffer.

@defun active-minibuffer-window
This function returns the window of the currently active minibuffer, or
@code{nil} if there is no active minibuffer.
@end defun

It is not sufficient to determine whether a given window shows the
currently active minibuffer by comparing it with the result of
@code{(minibuffer-window)}, because there can be more than one
minibuffer window if there is more than one frame.

@defun minibuffer-window-active-p window
This function returns non-@code{nil} if @var{window} shows the currently
active minibuffer.
@end defun

The following two options control whether minibuffer windows are resized
automatically and how large they can get in the process.

@defopt resize-mini-windows
This option specifies whether minibuffer windows are resized
automatically.  The default value is @code{grow-only}, which means that
a minibuffer window by default expands automatically to accommodate the
text it displays and shrinks back to one line as soon as the minibuffer
gets empty.  If the value is @code{t}, Emacs will always try to fit the
height of a minibuffer window to the text it displays (with a minimum of
one line).  If the value is @code{nil}, a minibuffer window never
changes size automatically.  In that case the window resizing commands
(@pxref{Resizing Windows}) can be used to adjust its height.
@end defopt

@defopt max-mini-window-height
This option provides a maximum height for resizing minibuffer windows
automatically.  A floating-point number specifies the maximum height
as a fraction of the frame's height; an integer specifies the maximum
height in units of the frame's canonical character height
(@pxref{Frame Font}).  The default value is 0.25.
@end defopt

Note that the values of the above two variables take effect at display
time, so let-binding them around code which produces echo-area messages
will not work.  If you want to prevent resizing of minibuffer windows
when displaying long messages, bind the @code{message-truncate-lines}
variable instead (@pxref{Echo Area Customization}).

The option @code{resize-mini-windows} does not affect the behavior of
minibuffer-only frames (@pxref{Frame Layout}).  The following option
allows to automatically resize such frames as well.

@defopt resize-mini-frames
If this is @code{nil}, minibuffer-only frames are never resized
automatically.

If this is a function, that function is called with the
minibuffer-only frame to be resized as sole argument.  At the time
this function is called, the buffer of the minibuffer window of that
frame is the buffer whose contents will be shown the next time that
window is redisplayed.  The function is expected to fit the frame to
the buffer in some appropriate way.

Any other non-@code{nil} value means to resize minibuffer-only frames by
calling @code{fit-mini-frame-to-buffer}, a function that behaves like
@code{fit-frame-to-buffer} (@pxref{Resizing Windows}) but does not strip
leading or trailing empty lines from the buffer text.
@end defopt


@node Minibuffer Contents
@section Minibuffer Contents
@cindex access minibuffer contents
@cindex minibuffer contents, accessing

  These functions access the minibuffer prompt and contents.

@defun minibuffer-prompt
This function returns the prompt string of the currently active
minibuffer.  If no minibuffer is active, it returns @code{nil}.
@end defun

@defun minibuffer-prompt-end
This function returns the current
position of the end of the minibuffer prompt, if a minibuffer is
current.  Otherwise, it returns the minimum valid buffer position.
@end defun

@defun minibuffer-prompt-width
This function returns the current display-width of the minibuffer
prompt, if a minibuffer is current.  Otherwise, it returns zero.
@end defun

@defun minibuffer-contents
This function returns the editable
contents of the minibuffer (that is, everything except the prompt) as
a string, if a minibuffer is current.  Otherwise, it returns the
entire contents of the current buffer.
@end defun

@defun minibuffer-contents-no-properties
This is like @code{minibuffer-contents}, except that it does not copy text
properties, just the characters themselves.  @xref{Text Properties}.
@end defun

@deffn Command delete-minibuffer-contents
This command erases the editable contents of the minibuffer (that is,
everything except the prompt), if a minibuffer is current.  Otherwise,
it erases the entire current buffer.
@end deffn

@node Recursive Mini
@section Recursive Minibuffers
@cindex recursive minibuffers

  These functions and variables deal with recursive minibuffers
(@pxref{Recursive Editing}):

@defun minibuffer-depth
This function returns the current depth of activations of the
minibuffer, a nonnegative integer.  If no minibuffers are active, it
returns zero.
@end defun

@defopt enable-recursive-minibuffers
If this variable is non-@code{nil}, you can invoke commands (such as
@code{find-file}) that use minibuffers even while the minibuffer is
active.  Such invocation produces a recursive editing level for a new
minibuffer.  By default, the outer-level minibuffer is invisible while
you are editing the inner one.  If you have
@code{minibuffer-follows-selected-frame} set to @code{nil}, you can
have minibuffers visible on several frames at the same time.
@xref{Basic Minibuffer,,, emacs}.

If this variable is @code{nil}, you cannot invoke minibuffer commands
when the minibuffer is active, not even if you switch to another window
to do it.
@end defopt

@c Emacs 19 feature
If a command name has a property @code{enable-recursive-minibuffers}
that is non-@code{nil}, then the command can use the minibuffer to read
arguments even if it is invoked from the minibuffer.  A command can
also achieve this by binding @code{enable-recursive-minibuffers}
to @code{t} in the interactive declaration (@pxref{Using Interactive}).
The minibuffer command @code{next-matching-history-element} (normally
@kbd{M-s} in the minibuffer) does the latter.

@node Inhibiting Interaction
@section Inhibiting Interaction

It's sometimes useful to be able to run Emacs as a headless server
process that responds to commands given over a network connection.
However, Emacs is primarily a platform for interactive usage, so many
commands prompt the user for feedback in certain anomalous situations.
This makes this use case more difficult, since the server process will
just hang waiting for user input.

@vindex inhibit-interaction
Binding the @code{inhibit-interaction} variable to something
non-@code{nil} makes Emacs signal a @code{inhibited-interaction} error
instead of prompting, which can then be used by the server process to
handle these situations.

Here's a typical use case:

@lisp
(let ((inhibit-interaction t))
  (respond-to-client
   (condition-case err
       (my-client-handling-function)
     (inhibited-interaction err))))
@end lisp

If @code{my-client-handling-function} ends up calling something that
asks the user for something (via @code{y-or-n-p} or
@code{read-from-minibuffer} or the like), an
@code{inhibited-interaction} error is signalled instead.  The server
code then catches that error and reports it to the client.

@node Minibuffer Misc
@section Minibuffer Miscellany

@defun minibufferp &optional buffer-or-name live
This function returns non-@code{nil} if @var{buffer-or-name} is a
minibuffer.  If @var{buffer-or-name} is omitted or @code{nil}, it
tests the current buffer.  When @var{live} is non-@code{nil}, the
function returns non-@code{nil} only when @var{buffer-or-name} is an
active minibuffer.
@end defun

@defvar minibuffer-setup-hook
This is a normal hook that is run whenever a minibuffer is entered.
@xref{Hooks}.
@end defvar

@defmac minibuffer-with-setup-hook function &rest body
This macro executes @var{body} after arranging for the specified
@var{function} to be called via @code{minibuffer-setup-hook}.  By
default, @var{function} is called before the other functions in the
@code{minibuffer-setup-hook} list, but if @var{function} is of the
form @w{@code{(:append @var{func})}}, @var{func} will be called
@emph{after} the other hook functions.

The @var{body} forms should not use the minibuffer more than once.  If
the minibuffer is re-entered recursively, @var{function} will only be
called once, for the outermost use of the minibuffer.
@end defmac

@defvar minibuffer-exit-hook
This is a normal hook that is run whenever a minibuffer is exited.
@xref{Hooks}.
@end defvar

@defvar minibuffer-help-form
@anchor{Definition of minibuffer-help-form}
The current value of this variable is used to rebind @code{help-form}
locally inside the minibuffer (@pxref{Help Functions}).
@end defvar

@defvar minibuffer-scroll-window
@anchor{Definition of minibuffer-scroll-window}
If the value of this variable is non-@code{nil}, it should be a window
object.  When the function @code{scroll-other-window} is called in the
minibuffer, it scrolls this window (@pxref{Textual Scrolling}).
@end defvar

@defun minibuffer-selected-window
This function returns the window that was selected just before the
minibuffer window was selected.  If the selected window is not a
minibuffer window, it returns @code{nil}.
@end defun

@vindex minibuffer-message-timeout
@defun minibuffer-message string &rest args
This function displays @var{string} temporarily at the end of the
minibuffer text, for a few seconds, or until the next input event
arrives, whichever comes first.  The variable
@code{minibuffer-message-timeout} specifies the number of seconds to
wait in the absence of input.  It defaults to 2.  If @var{args} is
non-@code{nil}, the actual message is obtained by passing @var{string}
and @var{args} through @code{format-message}.  @xref{Formatting Strings}.
@end defun

@deffn Command minibuffer-inactive-mode
This is the major mode used in inactive minibuffers.  It uses
keymap @code{minibuffer-inactive-mode-map}.  This can be useful
if the minibuffer is in a separate frame.  @xref{Minibuffers and Frames}.
@end deffn

debug log:

solving 185d355ba7 ...
found 185d355ba7 in https://git.savannah.gnu.org/cgit/emacs.git

(*) Git path names are given by the tree(s) the blob belongs to.
    Blobs themselves have no identifier aside from the hash of its contents.^

Code repositories for project(s) associated with this external index

	https://git.savannah.gnu.org/cgit/emacs.git
	https://git.savannah.gnu.org/cgit/emacs/org-mode.git

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.