Macintosh Terminal Pocket Guide

Creating and Running Shell Scripts

To create a shell script, simply put bash commands into a file as you would type them. For example, you could put these lines into a file called myscript:

echo "Here are your files:"
ls

When you run the script, its commands will run in order:

Here are your files:
file1.txt   file2.pdf

There are several ways to run a shell script:

Prepend #!/bin/bash and make the file executable

This is the most common way to run scripts. Add the following line to the top of the script file:

#!/bin/bash

It must be the first line of the file, left-justified. The result in our example looks like this:

#!/bin/bash
echo "Here are your files:"
ls

Then make the file executable:

➜ chmod +x myscript

Move it into a directory in your search path. Then run it like any other command:

➜ myscript

Alternatively, run the script from your current directory by prepending “./” (indicating the current directory) so the shell finds the script:

➜ ./myscript

The current directory is generally not in your search path for security reasons. You wouldn’t want a local script named, say, “ls” to override the real ls command unexpectedly.

Pass to bash

You can run bash directly as a command. It will interpret its argument as the name of a script and run it:

➜ bash myscript

Run in current shell with “.” or source

The preceding methods run your script as an independent entity that has no effect on your current shell.^[34] If you want your script to make changes to your current shell (setting variables, changing directory, ...