Re: [PATCH] exec: Print absolute paths for command location queries

On 06/06/2026 16:36, Kerin Millar wrote:
> POSIX requires that, when reporting the location of a utility found by
> searching PATH (or one named with a slash), the pathname written by
> type, command -v and command -V be absolute:
> 
>      Executable utilities, regular built-in utilities, command_names
>      including a <slash> character, and any implementation-provided
>      functions that are found using the PATH variable [...] shall be
>      written as absolute pathnames.
> 
> Presently, dash fails to conform in this regard. Address this issue by
> incorporating a helper function that prefixes relative pathnames with
> the shell's cached current working directory.

Hi,

Although this ensures that the written path is absolute whenever 
possible, it does not ensure that the written path corresponds to the 
command that would be executed. Although curdir cannot be altered by the 
user, that does not mean it should be trusted for this purpose, because 
the file system may have changed after the current directory was set.

Consider:

   cd /tmp
   mkdir a
   cd a
   ln -s /bin/ls
   PATH=. command -v ls # should print /tmp/a/ls or /tmp/a/./ls
   mv /tmp/a /tmp/b
   PATH=. command -v ls # must not print /tmp/a/ls or /tmp/a/./ls

Printing /tmp/a/ls for that last line is worse than printing ./ls: ./ls 
may not be absolute but at least resolves to the command that would be 
executed.

bash does not appear to consider this requirement useful, so in 
non-POSIX mode just prints ./ls. In POSIX mode it prints /tmp/a/./ls twice.

ksh prints /tmp/a/ls twice, regardless of POSIX mode.

zsh prints ./ls twice, regardless of sh mode.

yash correctly prints /tmp/a/./ls, followed by /tmp/b/./ls.

My shell, gwsh, also prints /tmp/a/./ls, followed by /tmp/b/./ls.

I think leaving it as printing a correct relative path is better than 
printing a possibly wrong absolute path, personally. A change to print a 
correct absolute path would have my support though, for whatever that is 
worth.

Cheers,
Harald van Dijk