bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Thierry Volpiatto]

Hello all,

It is unclear how to use MODES argument of
file-modes-symbolic-to-number, actually the correct way to use it is the
second example below, I found it by reading the read-file-modes code and
saw it removes all "-" to setup MODES arg to pass to
file-modes-symbolic-to-number. I was surprized to see the first example
is not supported, thus the docstring of file-modes-symbolic-to-number is
pretty unclear:

,----
| MODES is the string to convert, it should match
| "[ugoa]*([+-=][rwxXstugo]*)+,...".
`----

At least an example in docstring or manual would be welcome.

(format "%o" (file-modes-symbolic-to-number "u=rwx,g=r-x,o=---"))
"740"
(format "%o" (file-modes-symbolic-to-number "u=rwx,g=rx,o="))
"750"

Thanks.


In GNU Emacs 28.2 (build 1, x86_64-pc-linux-gnu, Motif Version 2.3.8, cairo version 1.16.0)
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<#secure method=pgpmime mode=sign>

-- 
Thierry

bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Thierry Volpiatto]

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Here a simple patch to summarize what's wrong:

diff --git a/lisp/files.el b/lisp/files.el
index 5b989902bc3..576eb22c49f 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -8363,6 +8363,7 @@ If CHAR is in [Xugo], the value is taken from FROM (or 0 if omitted)."
   (cond ((eq char ?r) #o0444)
 	((eq char ?w) #o0222)
 	((eq char ?x) #o0111)
+        ((eq char ?-) #o0000)
 	((eq char ?s) #o6000)
 	((eq char ?t) #o1000)
 	;; Rights relative to the previous file modes.
@@ -8393,7 +8394,7 @@ as in \"og+rX-w\"."
       (let ((num-right 0)
 	    char-right)
 	(while (memq (setq char-right (pop list-rights))
-		     '(?r ?w ?x ?X ?s ?t ?u ?g ?o))
+		     '(?r ?w ?x ?X ?s ?t ?u ?g ?o ?-))
 	  (setq num-right
 		(logior num-right
 			(file-modes-char-to-right char-right num-rights))))

-- 
Thierry

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bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Andreas Schwab]

On Feb 22 2023, Thierry Volpiatto wrote:

> (format "%o" (file-modes-symbolic-to-number "u=rwx,g=r-x,o=---"))
> "740"

This is the correct interpretation of the mode string, with "g=r-x"
meaning the same as "g=r,g-x" or just "g=r".

See
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/chmod.html
for the full syntax.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Thierry Volpiatto]

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Andreas Schwab <schwab@suse.de> writes:

> On Feb 22 2023, Thierry Volpiatto wrote:
>
>> (format "%o" (file-modes-symbolic-to-number "u=rwx,g=r-x,o=---"))
>> "740"
>
> This is the correct interpretation of the mode string, with "g=r-x"
> meaning the same as "g=r,g-x" or just "g=r".

So how do you interpret this: "drwxr-x---" (from file-attributes)?
"u=?,g=?,o=?" to pass it to file-modes-symbolic-to-number?

(nth 8 (file-attributes "/home/user"))
"drwxr-x---"

(read-file-modes nil "/home/user")
#o750

Thanks.

> See
> https://pubs.opengroup.org/onlinepubs/9699919799/utilities/chmod.html
> for the full syntax.


-- 
Thierry

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bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Andreas Schwab]

On Feb 22 2023, Thierry Volpiatto wrote:

> So how do you interpret this: "drwxr-x---" (from file-attributes)?

This is not a symbolic mode.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Thierry Volpiatto]

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Andreas Schwab <schwab@suse.de> writes:

> On Feb 22 2023, Thierry Volpiatto wrote:
>
>> So how do you interpret this: "drwxr-x---" (from file-attributes)?
>
> This is not a symbolic mode.

(file-modes-number-to-symbolic #o750)
=>"-rwxr-x---"

I will reformulate my question:

How one convert the output of (nth 8 (file-attributes "/home/user")) to
numeric mode?

-- 
Thierry

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bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Gregory Heytings]

>
> How one convert the output of (nth 8 (file-attributes "/home/user")) to 
> numeric mode?
>

(file-modes "/home/user")

bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Thierry Volpiatto]

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Gregory Heytings <gregory@heytings.org> writes:

>>
>> How one convert the output of (nth 8 (file-attributes "/home/user"))
>> to numeric mode?
>>
>
> (file-modes "/home/user")

Yes, thanks I know this one, what I want to convert is e.g. "-rwxr-x---"
to number.

(file-modes-number-to-symbolic #o750)
"-rwxr-x---"
Means
"-|rwx|r-x|---"
rwx for user, rx for group and nothing for others.

What I mean is that file-modes-symbolic-to-number returns the right
value with MODES "u=rwx,g=rx,o=" but the wrong value with
"u=rwx,g=r-x,o=---".
This is why read-file-modes remove the "-" for passing the string as
MODES to file-modes-symbolic-to-number.

So shouldn't file-modes-symbolic-to-number supports "u=rwx,g=r-x,o=---"
and "u=rwx,g=rx,o=" in the same way.

I ask because I had to read code to understand this as I can't
understand the docstring.

-- 
Thierry

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bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Gregory Heytings]

>>> How one convert the output of (nth 8 (file-attributes "/home/user")) 
>>> to numeric mode?
>>
>> (file-modes "/home/user")
>
> Yes, thanks I know this one, what I want to convert is e.g. "-rwxr-x---" 
> to number.
>

(defun symbolic-mode-to-number (mode)
   (string-to-number
    (replace-regexp-in-string
     "[^0]" "1"
     (string-replace "-" "0" mode))
    2))

bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Thierry Volpiatto]

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Gregory Heytings <gregory@heytings.org> writes:

>>>> How one convert the output of (nth 8 (file-attributes
>>>> "/home/user")) to numeric mode?
>>>
>>> (file-modes "/home/user")
>>
>> Yes, thanks I know this one, what I want to convert is
>> e.g. "-rwxr-x---" to number.
>>
>
> (defun symbolic-mode-to-number (mode)
>   (string-to-number
>    (replace-regexp-in-string
>     "[^0]" "1"
>     (string-replace "-" "0" mode))
>    2))

Nice! I never used the BASE argument of string-to-number probably due to
my catastrophic math level :-), however this is very basic and doesn't
cover modes like "-rwxrwxrwt" or "-rwsr-xr-x".

I already wrote the needed functions for my needs (helm), however what I
had like is to clarify the usage of `file-modes-symbolic-to-number' in
docstring (examples?).
As Andrea pointed the MODES argument handle (+-=) like chmod would do
i.e. the function returns the numeric mode that for example chmod would set on
a file. Once you know it that's fine , you remove the "-" in MODES like
read-file-modes does otherwise you may think it interpret the mode that
a file already has.

Thanks.

-- 
Thierry

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bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Eli Zaretskii]

> Cc: Andreas Schwab <schwab@suse.de>, 61708@debbugs.gnu.org
> Date: Wed, 22 Feb 2023 21:40:21 +0000
> From: Gregory Heytings <gregory@heytings.org>
> 
> 
> >>> How one convert the output of (nth 8 (file-attributes "/home/user")) 
> >>> to numeric mode?
> >>
> >> (file-modes "/home/user")
> >
> > Yes, thanks I know this one, what I want to convert is e.g. "-rwxr-x---" 
> > to number.
> >
> 
> (defun symbolic-mode-to-number (mode)
>    (string-to-number
>     (replace-regexp-in-string
>      "[^0]" "1"
>      (string-replace "-" "0" mode))
>     2))

Maybe we should have a knob in file-attributes or in
file-attribute-modes to return the modes as either a number or in
symbolic form suitable for file-modes-symbolic-to-number?

bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Thierry Volpiatto]

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Eli Zaretskii <eliz@gnu.org> writes:

>> Cc: Andreas Schwab <schwab@suse.de>, 61708@debbugs.gnu.org
>> Date: Wed, 22 Feb 2023 21:40:21 +0000
>> From: Gregory Heytings <gregory@heytings.org>
>> 
>> 
>> >>> How one convert the output of (nth 8 (file-attributes "/home/user")) 
>> >>> to numeric mode?
>> >>
>> >> (file-modes "/home/user")
>> >
>> > Yes, thanks I know this one, what I want to convert is e.g. "-rwxr-x---" 
>> > to number.
>> >
>> 
>> (defun symbolic-mode-to-number (mode)
>>    (string-to-number
>>     (replace-regexp-in-string
>>      "[^0]" "1"
>>      (string-replace "-" "0" mode))
>>     2))
>
> Maybe we should have a knob in file-attributes or in
> file-attribute-modes to return the modes as either a number or in
> symbolic form suitable for file-modes-symbolic-to-number?

That's a good idea.

-- 
Thierry

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bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Andreas Schwab]

On Feb 22 2023, Thierry Volpiatto wrote:

> (file-modes-number-to-symbolic #o750)

This function is misnamed.  It doesn't return a symbolic mode, but a
different text representation, and certainly isn't the inverse of
file-modes-symbolic-to-number.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Andreas Schwab]

On Feb 22 2023, Gregory Heytings wrote:

> (defun symbolic-mode-to-number (mode)
>   (string-to-number
>    (replace-regexp-in-string
>     "[^0]" "1"
>     (string-replace "-" "0" mode))
>    2))

Apart from being misnamed, it doesn't handle tTsS.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

bug#61708: 28.2; file-modes-symbolic-to-number inconsistency

[Gregory Heytings]

>> (defun symbolic-mode-to-number (mode)
>>   (string-to-number
>>    (replace-regexp-in-string
>>     "[^0]" "1"
>>     (string-replace "-" "0" mode))
>>    2))
>
> Apart from being misnamed, it doesn't handle tTsS.
>

Yes, that was just a quick PoC.  It doesn't handle the leading letter, 
either.