AW: [PATCH] environ.7: Document the valid values of pathnames for SHELL, PAGER and EDITOR/VISUAL

[Walter Harms <wharms@bfs.de>]

FYI:
i took a dive into busybox to see what is expected for SHELL there.
According to the code the value is used like the path in
struct passwd.  In the end the value was executed via execv.

I have to admit that i always use a absolute value and was curious.

jm2c,
 wh
________________________________________
Von: Alejandro Colomar <alx.manpages@gmail.com>
Gesendet: Dienstag, 19. Januar 2021 21:45:00
An: mtk.manpages@gmail.com
Cc: roucaries.bastien@gmail.com; Bastien Roucariès; linux-man@vger.kernel.org; Dr . Tobias Quathamer; Vincent Lefevre; Alejandro Colomar
Betreff: [PATCH] environ.7: Document the valid values of pathnames for SHELL, PAGER and EDITOR/VISUAL

From: Bastien Roucariès <rouca@debian.org>

The environ(7) man page says:

       SHELL  The pathname of the user's login shell.

       PAGER  The user's preferred utility to display text files.

       EDITOR/VISUAL
              The user's preferred utility to edit text files.

but doesn't say whether the pathnames must be absolute or they can
be resolved using $PATH, or whether they can have options.

Note that at least for SHELL, this is not specified by POSIX.
This issue was raised in the Austin Group mailing-list, and the answer
is that "what constitutes a valid value for a platform
should be documented" [1].

Since OpenSSH assumes that $SHELL is an absolute pathname (when set),
it is supposed that the documentation should be:

       SHELL  The absolute pathname of the user's login shell.

For PAGER, POSIX says: "Any string acceptable as a command_string
operand to the sh -c command shall be valid."

For EDITOR, it does not need to be an absolute pathname since POSIX
gives the example:

  EDITOR=vi fc

and since it is specified as "the name of a utility", It assumes that
arguments (options) must not be provided. Page 3013 about "more", it
is said: "If the last pathname component in EDITOR is either vi or ex,
[...]", thus again, it is assumed to be a pathname.

For VISUAL, POSIX says: "Determine a pathname of a utility to invoke
when the visual command [...]", thus it is also a pathname. It is not
clear whether the pathname must be absolute, but for consistency with
EDITOR, it will be resolved using $PATH.

[1] https://www.mail-archive.com/austin-group-l@opengroup.org/msg01399.html

Reported-by: Vincent Lefevre <vincent@vinc17.net>
Signed-off-by: Bastien Roucaries <rouca@debian.org>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
---
 man7/environ.7 | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/man7/environ.7 b/man7/environ.7
index 7d2bc5a86..b30f9a38e 100644
--- a/man7/environ.7
+++ b/man7/environ.7
@@ -113,16 +113,22 @@ The current working directory.
 Set by some shells.
 .TP
 .B SHELL
-The pathname of the user's login shell.
+The absolute pathname of the user's login shell.
 .TP
 .B TERM
 The terminal type for which output is to be prepared.
 .TP
 .B PAGER
 The user's preferred utility to display text files.
+Any string acceptable as a command_string operand to the
+.I sh -c
+command shall be valid.
 .TP
 .BR EDITOR / VISUAL
 The user's preferred utility to edit text files.
+Any string acceptable as a command_string operand to the
+.I sh -c
+command shall be valid.
 .\" .TP
 .\" .B BROWSER
 .\" The user's preferred utility to browse URLs. Sequence of colon-separated
--
2.30.0