In my previous blog posts, we covered the basics of using the shell and introduced shell scripting for beginners. Now that you have a solid foundation in shell scripting, it’s time to explore some advanced techniques and best practices that will help you write more efficient, robust, and maintainable scripts. In this blog post, we will discuss error handling, command substitution, process management, and best practices for writing shell scripts. We will also provide some resources for further learning.

Error Handling

Error handling is an essential aspect of writing robust shell scripts. By default, shell scripts continue to execute subsequent commands even if an error occurs. To change this behavior and make your script exit immediately if a command fails, you can use the set -e option:

set -e

# Your script here

You can also use the trap command to define custom error handling behavior. For example, you can create a cleanup function that will be called if your script exits unexpectedly:


function cleanup() {
  echo "Cleaning up before exiting..."
  # Your cleanup code here

trap cleanup EXIT

# Your script here

Command Substitution

Command substitution allows you to capture the output of a command and store it in a variable. This can be useful for processing the output of a command within your script. There are two ways to perform command substitution:

  1. Using backticks (` `):
  1. Using $():

The $() syntax is preferred because it is more readable and can be easily nested.

Process Management

Shell scripts often need to manage background processes, such as starting, stopping, or monitoring them. Here are some useful commands for process management:

  • &: Run a command in the background by appending an ampersand (&) to the command.
long_running_command &
  • wait: Wait for a background process to complete before continuing with the script.
long_running_command &
  • kill: Terminate a process by sending a signal to it.
kill -9 process_id
  • ps: List running processes and their process IDs.
ps aux

Best Practices

Here are some best practices for writing shell scripts:

  • Use meaningful variable and function names.
  • Add comments to explain complex or non-obvious code.
  • Use indentation and whitespace to improve readability.
  • Keep your scripts modular by breaking them into smaller functions.
  • Use the local keyword to limit the scope of variables within functions.
  • Always quote your variables to prevent issues with spaces and special characters.
  • Use the [[ ]] syntax for conditional expressions, as it is more robust than [ ].


To further improve your shell scripting skills, here are some resources:

  • Google Shell Style Guide: A comprehensive style guide for writing shell scripts, created by Google.
  • ShellCheck: A static analysis tool for shell scripts that can help you identify and fix potential issues in your code.
  • Awesome Shell: A curated list of awesome command-line frameworks, toolkits, guides, and other resources for shell scripting.

In conclusion, mastering advanced techniques and best practices in shell scripting will help you write more efficient, robust, and maintainable scripts. By understanding error handling, command substitution, process management, and following best practices, you will be well on your way to becoming a shell scripting expert.