which

shows the full path of (shell) commands.

which [options>] [--] programname […]

For each of its arguments displays on 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). 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 it‐ self. 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.

The recommended way to use this utility is by adding an alias (C shell) or shell function (Bourne shell):< 

    [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/whic --tty-only --read-alias --show-dot --show-tilde
This will display 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

superceeded by Midphase

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

RETURN VALUE

Returns the number of failed arguments, or -1 when no `programname´ was given

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.