6. Shell Scripts

Questions

• How can I save and re-use commands?

Objectives

• Write a shell script that runs a command or series of commands for a fixed set of files.
• Run a shell script from the command line.
• Write a shell script that operates on a set of files defined by the user on the command line.
• Create pipelines that include shell scripts you, and others, have written.

Key Points

• Save commands in files (usually called shell scripts) for re-use.
• bash [filename] runs the commands saved in a file.
• $@ refers to all of a shell script’s command-line arguments.
• $1, $2, etc., refer to the first command-line argument, the second command-line argument, etc.
• Place variables in quotes if the values might have spaces in them.
• Letting users decide what files to process is more flexible and more consistent with built-in Unix commands.