ls -0 > /dev/null 2>&1

[anneng]

suppressing the error output (stderr) of the ls -0 command, redirect it to standard output (stdout), writing it to /dev/null thereby immediately discarding it.

This technique is commonly used to tell whether a command exists, which you can use for handling different operating systems, automatically installing packages, downloading files, and most importantly defending your scripts and systems from unexpected exceptions.

function cmd_exists() {
command -v $1 > /dev/null 2>&1
}

cmd_exists ls; echo $?

cmd_exists sl; echo $?