usage: command not found

Question

I have a file parsing option flags from command line input, and if you pass in -h, it's giving an error.

h)  
    usage
    exit 1
;;

returns: usage: command not found

Does anybody know what’s going on here? I've found many examples that use usage, so I would think it should work. I can’t seem to find any relevant info on it searching google.

Answer 1

What you are missing is a function definition of usage:

function usage {
    cat <<-USAGE
         Now you can define your usage here
         take as many lines as you want. When
         you finish, just put "USAGE" on a line
         by itself.
    USAGE
}

Put this BEFORE the call of usage. Remember that the line with USAGE must be preceded only by tabs.

Answer 2

You need add to your shell script before you call the usage the next:

usage() {
    echo  "$0: some help text"
}

Answer 3

Those working examples define a function called usage in their source.

As you see, it gets called, when you provide the -h flag.

The usual reason behind moving it to a function is that

• it doesn't clutter the code
• can be reused, e.g. when you provide invalid arguments.

Answer 4

usage is not a command, but the common name for a custom shell function you supply that outputs usage information for your script.