Macintosh Terminal Pocket Guide

Command-Line Arguments

Shell scripts can accept command-line arguments just like other commands.^[37] Within a shell script, you can refer to these arguments as $1, $2, $3, and so on:

➜ cat myscript
#!/bin/bash
echo "My name is $1 and I come from $2"

➜ ./myscript Johnson Wisconsin
My name is Johnson and I come from Wisconsin
➜ ./myscript Bob
My name is Bob and I come from

Your script can test the number of arguments it received with $#:

if [ $# -lt 2 ]
then
  echo "$0 error: you must supply two arguments"
else
  echo "My name is $1 and I come from $2"
fi

The special value $0 contains the name of the script, and is handy for usage and error messages:

➜ ./myscript Bob
./myscript error: you must supply two arguments

To iterate over all command-line arguments, use a for loop with the special variable $@, which holds all arguments:

for arg in $@
do
  echo "I found the argument $arg"
done

^[37] To a shell script, there is no difference between an option and an argument. They are all considered arguments.