Question

I am writing a shell program that takes in three arguments:

• an integer to determine the function of the program
• a file used by the program

The command is of the form myProgram num file. However, I want the program to output an error if the command only has 0, 1, or more than 2 arguments. That is, if I type “myProgram”, “myProgram num”, or “myProgram num file anotherWord”, an error will be printed to the screen. Does anyone know how I could implement this into my existing code?

Answer 1

The built-in variable $# contains the number of arguments that were passed to the script. You use this to check if there are enough arguments like so:

#!/bin/bash

if [ $# -ne 2 ]; then
    echo "Usage: myProgram num file" >&2
    exit 1
fi

# The rest of your script.