LinuxGuide.it > Linux Man Page: "which"

 

 
Search with Google

 

The Linux Documentation Project maintains an archive of snaphots of the (English language) core Linux manual pages that are maintained by Michael Kerrisk. Corrections and additions are welcome, but review the "Help Wanted" list, first.

Man pages belonging to programs are usually distributed together with those programs. Therefore, the core Linux man-pages mainly contains the pages for system calls and library routines, special devices, and file formats. However, it also contains documentation for a few programs, in cases where the authors or maintainers of the program do not distribute man pages themselves.

This page is part of release 3.11 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages

 

man page(1) manual page Table of Contents

Name

which - shows the full path of (shell) commands.

Synopsis

which [options] [--] programname [...]

Description

Which takes one or more arguments. For each of its arguments it prints to stdout the full path of the executables that would have been executed when this argument had been entered at the shell prompt. It does this by searching for an executable or script in the directories listed in the environment variable PATH using the same algorithm as bash(1) .

This man page is generated from the file which.texinfo.

Options

--all, -a
Print all matching executables in PATH, not just the first.

--read-alias, -i
Read aliases from stdin, reporting matching ones on stdout. This is useful in combination with using an alias for which itself. For example alias which=¬´¬´alias | which -i¬´¬´.

--skip-alias
Ignore option ‘--read-alias¬´, if any. This is useful to explicity search for normal binaries, while using the ‘--read-alias¬´ option in an alias or function for which.

--read-functions
Read shell function definitions from stdin, reporting matching ones on stdout. This is useful in combination with using a shell function for which itself. For example: which() { declare -f | which --read-functions $@ } export -f which

--skip-functions
Ignore option ‘--read-functions¬´, if any. This is useful to explicity search for normal binaries, while using the ‘--read-functions¬´ option in an alias or function for which.

--skip-dot
Skip directories in PATH that start with a dot.

--skip-tilde
Skip directories in PATH that start with a tilde and executables which reside in the HOME directory.

--show-dot
If a directory in PATH starts with a dot and a matching executable was found for that path, then print “./programname” rather than the full path.

--show-tilde
Output a tilde when a directory matches the HOME directory. This option is ignored when which is invoked as root.

--tty-only
Stop processing options on the right if not on tty.

--version,-v,-V
Print version information on standard output then exit successfully.

--help
Print usage information on standard output then exit successfully.

Return Value

Which returns the number of failed arguments, or -1 when no ‘programname¬´ was given.

Example

The recommended way to use this utility is by adding an alias (C shell) or shell function (Bourne shell) for which like the following:

[ba]sh:

which ()
{
(alias; declare -f) | /usr/bin/which --tty-only --read-alias --read-functions --show-tilde --show-dot $@ }
export -f which

[t]csh:

alias which ¬´alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde¬´

This will print the readable ~/ and ./ when starting which from your prompt, while still printing the full path when used from a script:

> which q2
~/bin/q2
> echo ‘which q2‘
/home/carlo/bin/q2

Bugs

The HOME directory is determined by looking for the HOME environment variable, which aborts when this variable doesn¬´t exist. Which will consider two equivalent directories to be different when one of them contains a path with a symbolic link.

Author

Carlo Wood <carlo@gnu.org>

See Also

bash(1)


Table of Contents

use open software!