which (1) - Linux Manuals
which: locate a command
NAME
which - locate a command
SYNOPSIS
which [-a] filename ...DESCRIPTION
which returns the pathnames of the files (or links) which would be executed in the current environment, had its arguments been given as commands in a strictly POSIX-conformant shell. It does this by searching the PATH for executable files matching the names of the arguments. It does not canonicalize path names.OPTIONS
- -a
 - print all matching pathnames of each argument
 
EXIT STATUS
- 0
 - if all specified commands are found and executable
 - 1
 - if one or more specified commands is nonexistent or not executable
 - 2
 - 
if an invalid option is specified