Locate a program file in the user's path.
For each of its arguments which prints to stdout the full path of the executable(s). It does this by searching the directories listed in the environment variable PATH.
Syntax which [options] [--] program_name [...] 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 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 "./program_name" 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 A useful way to use this utility is by adding an alias for which like the following: alias which='which --tty-only --show-tilde --show-dot' 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 Aliases are also supported, through the use of an alias for which itself. An example alias for which that is using this feature is as follows: alias which='alias | which --tty-only --read-alias --show-tilde --show-dot' This will print the output of alias for each alias that matches one of the given arguments. For example, using this alias on itself in a tcsh: $ alias which alias \| /usr/bin/which -i !\* $ which which which (alias | ./which -i !*) /usr/bin/which 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.
Some shells may provide a builtin which command which is similar or identical to this utility.
"A man should never be ashamed to own he has been in the wrong, which is saying in other words, that he is wiser today than he was yesterday" ~ Alexander Pope (thoughts on various subjects)
Related linux commands:
pwd - Print Working Directory
hash - Remember the full pathname of a name argument
pathchk - Check file name portability
whereis - Search the user's $path, man pages and source files for a program
Equivalent Windows commands: WHERE - Locate and display files in a directory tree.
Equivalent PowerShell cmdlet: (get-command $file).Definition
Equivalents in Batch/Perl/VBScript - WHICH Scripts