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Date: Thu, 23 May 2024 15:45:10 +0200
From: Leah Neukirchen <>
To: Rich Felker <>
Cc: Collin Funk <>,
Subject: Re: getusershell should ignore comments and empty lines.

Rich Felker <> writes:

> It says:
>     "A hash mark (``#'') indicates the beginning of a comment;
>     subsequent characters up to the end of the line are not
>     interpreted by the routines which search the file."
> This isn't very clear whether # is only a comment on the beginning of
> a line (after potential whitespace?) or whether # appearing in a line
> with a shell pathname is a comment or part of the pathname. If it's a
> comment, it's not clear if whitespace before it is part of the shell
> pathname -- e.g. does "/bin/sh # best shell" define "/bin/sh" or
> "/bin/sh " as the shell pathname?
> It sounds like nobody ever thought about whitespace, quoting, or
> rigorous comment syntax here...


OpenBSD drops the rest of the line with "#" and ignores lines not
starting with a "/".

glibc drops the rest of the line with "#", elides spaces after the
entry, and skips everything before the first "/" (quite bold).

pam_shells skips all lines that don't start with a "/" and doesn't
handle "#" specially.

gnome-terminal just tries to find one line that matches exactly the
the shell

util-linux skips lines from getusershell that start with "#".
Likewise "seunshare".

Leah Neukirchen  <>

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