$ PIPELINE_DEBUG=1 LC_ALL=C.UTF-8 MANROFFSEQ='' MANWIDTH=80 \
man --warnings=all,mac -E UTF-8 -l -Tutf8 -Z doc/man/emacs.1 >/dev/null                  
Starting pipeline: (echo .nh && echo .de hy && echo .. && echo .na && echo .de ad && echo .. && cat) [input: {0, doc/man/emacs.1}, output: {-1, NULL}]
Started "decompressor", pid 1636161
Started "echo .nh && echo .de hy && echo ..", pid 1636162
  "echo .nh && echo .de hy && echo .." (1636162) -> 0
Started "echo .na && echo .de ad && echo ..", pid 1636163
  "echo .na && echo .de ad && echo .." (1636163) -> 0
Started "cat", pid 1636164
Starting pipeline: /usr/libexec/man-db/zsoelim | preconv -e UTF-8 | groff -mandoc -Z -wall -wmac -Tutf8  "cat" (1636164) -> 0
 [input: {-1, NULL}, output: {0, NULL}]
Started "/usr/libexec/man-db/zsoelim", pid 1636165
Started "preconv", pid 1636166
Started "groff", pid 1636167
source pipeline 0 returned error or EOF
Waiting for pipeline: (echo .nh && echo .de hy && echo .. && echo .na && echo .de ad && echo .. && cat) [input: {0, doc/man/emacs.1}, output: {-1, NULL}]
Active processes (1):
  "decompressor" (1636161) -> 0
Waiting for pipeline: /usr/libexec/man-db/zsoelim | preconv -e UTF-8 | groff -mandoc -Z -wall -wmac -Tutf8 [input: {-1, NULL}, output: {0, NULL}]
Active processes (3):
  "/usr/libexec/man-db/zsoelim" (1636165) -> -1
  "preconv" (1636166) -> -1
  "groff" (1636167) -> -1
Starting pipeline: zcat [input: {3, NULL}, output: {-1, NULL}]
Started "zcat", pid 1636168
Waiting for pipeline: zcat [input: {3, NULL}, output: {-1, NULL}]
Active processes (1):
  "zcat" (1636168) -> -1
Active processes (1):
  "zcat" (1636168) -> 0
Active processes (3):
  "/usr/libexec/man-db/zsoelim" (1636165) -> 0
  "preconv" (1636166) -> -1
  "groff" (1636167) -> -1
Active processes (2):
  "preconv" (1636166) -> 0
  "groff" (1636167) -> -1
troff: <standard input>:18: warning: macro 'SHX' not defined (possibly missing space after 'SH')
Active processes (1):
  "groff" (1636167) -> 0