Shell Scripting: Expert Recipes for Linux, Bash, and More

Summary

Wildcards can be very flexible and useful, but the price of this is vigilance; whenever using any kind of nonstandard character, you will need to consider how it will be treated by the shell. In some cases it will be passed through; in others it will be interpreted as having special meaning. It is not always obvious which is which — the rules are complex and not always easy to understand.

It is very important to be sure of how you process user-generated or externally sourced input strings. For example, if you do all of your testing expecting the user to provide nice filenames without spaces in them, your script will break when the user passes it a filename including spaces if you have not quoted the filename.

The next chapter deals with Conditional Execution, which uses a variety of tests of the state of the environment to control the flow of a shell script.