Detect if executable file is on user's PATH [duplicate]

Answer 1

You can use the command builtin, which is POSIX compatible:

if [ -x "$(command -v "$cmd")" ]; then
    echo "$cmd is in \$PATH"
fi

The executable check is needed because command -v detects functions and aliases as well as executables.

In Bash, you can also use type with the -P option, which forces a PATH search:

if type -P "$cmd" &>/dev/null; then
    echo "$cmd is in \$PATH"
fi

As already mentioned in the comments, avoid which as it requires launching an external process and might give you incorrect output in some cases.