[ACCEPTED]-Find out if a command exists on POSIX system-posix

Accepted answer
Score: 33

command -v is a POSIX specified command that does 3 what which does.

It is defined to to return 2 >0 when the command is not found or an error 1 occurs.

Score: 3

You could read the stdout/stderr of "which" into 9 a variable or an array (using backticks) rather 8 than checking for an exit code.

If the system 7 does not have a "which" or "where" command, you 6 could also grab the contents of the $PATH 5 variable, then loop over all the directories 4 and search for the given executable. That's 3 essentially what which does (although it 2 might use some caching/optimization of $PATH 1 results).

Score: 0

Actually, which is a shell script available in 11 git repository. The script seems to be POSIX compatible 10 and you could use it, if you take into account 9 copyright and license.

command -v as such is problematic 8 as it may output a shell function name, an 7 alias definition, a keyword, a builtin or 6 a non-executable file path. On the other 5 hand some path(s) output by which would not be 4 executed by shell if you run the respective 3 argument as such or as an argument for command.

A 2 POSIX shell function using command -v could be something 1 like

# $1 should be the basename of the command to be found.
# Outputs the absolute path of the command, or returns 1, if there is no
# such command in PATH executable by the caller and not shadowed by
# alias, builtin, keyword or shell function.
executable() {
    if cmd=$(unset -f -- "$1"; unalias -a; command -v -- "$1") \
        && [ -z "${cmd##/*}" ] && [ -x "$cmd" ]; then
        printf '%s\n' "$cmd"
        return 1

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