Re: [Buildroot] [PATCH 0/1] Build issue related to "command -v"

Hi all,

...

quoted

Meanwhile, 'which' is not standard, and right now, it misbehaves on
Debian by filling the screen with warnings.

'which' is a shell script that is trying to emulate a csh builtin.
I've NFI why people keep using it :-)

FYI Yes, version from the Debian's debianutils package was a shell script, but
other distros had GNU which [2], which is C code.

The equivalent bourne shell command is 'type'.

I also knew 'type' and was suspicious about 'command -v' support across
implemented shell, until I asked [3], because checkbashisms.pl [4] complains
about 'type' and it's ok with 'command -v'.

'type' is part of POSIX, but as part of the X/Open Systems Interfaces option
(XSI) [5] thus it might not be implemented on very small systems.
'command -v' is POSIX but not extension [6] thus it should be everywhere.

I tested 'command -v' is supported by commonly used shells (bash, dash, busybox
ash, zsh). Although so does 'type' thus I prefer to use 'command -v' instead of
'type' in shell scripts thus I can check them with checkbashisms.pl.

As for 'command -v' no idea what the POSIX committee had
for lunch that day :-)
It was probably they same day they added 'fc' (from ksh??)

I cannot comment that, but if you read their definition [5] and [6] has slightly
different purpose.

Kind regards,
Petr

[1] https://salsa.debian.org/debian/debianutils/-/commit/3a8dd10b4502f7bae8fc6973c13ce23fc9da7efb
[2] https://ftp.gnu.org/gnu/which/which-2.21.tar.gz
[3] https://unix.stackexchange.com/a/667293
[4] https://salsa.debian.org/debian/devscripts/-/blob/master/scripts/checkbashisms.pl
[5] https://pubs.opengroup.org/onlinepubs/9699919799/utilities/type.html
[6] https://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html

	David

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