osx man page for which

WHICH(1)						    BSD General Commands Manual 						  WHICH(1)

NAME
     which -- locate a program file in the user's path

SYNOPSIS
     which [-as] program ...

DESCRIPTION
     The which utility takes a list of command names and searches the path for each executable file that would be run had these commands actually
     been invoked.

     The following options are available:

     -a      List all instances of executables found (instead of just the first one of each).

     -s      No output, just return 0 if any of the executables are found, or 1 if none are found.

     Some shells may provide a builtin which command which is similar or identical to this utility.  Consult the builtin(1) manual page.

SEE ALSO
     builtin(1), csh(1), find(1), locate(1), whereis(1)

HISTORY
     The which command first appeared in FreeBSD 2.1.

AUTHORS
     The which utility was originally written in Perl and was contributed by Wolfram Schneider <wosch@FreeBSD.org>.  The current version of which
     was rewritten in C by Daniel Papasian <dpapasia@andrew.cmu.edu>.

BSD
								   June 21, 2002							       BSD