Bash

Bourne Again SHell, the standard shell for Linux and macOS.

When to Use

• Automating system tasks
• CI/CD pipelines
• File manipulation
• Glue code between CLIs

Quick Start

#!/bin/bash

NAME="World"
echo "Hello, $NAME!"

if [ -f "file.txt" ]; then
    echo "File exists"
else
    echo "File not found"
fi

Core Concepts

Variables

No data types. Everything is a string.

count=10
echo $count

Pipes and Redirection

• |: Pipe output of one command to input of next.
• >: Redirect output to file (overwrite).
• >>: Redirect output to file (append).

cat file.txt | grep "error" > errors.log

Exit Codes

Commands return 0 for success and non-zero for failure. Check with $?.

Best Practices

Do:

• Use set -e (e)xit on error
• Use set -u (u)nset variable usage is error
• Use set -o pipefail to catch errors in pipes
• Quote variables "$VAR" to handle spaces

Don’t:

• Parse ls output (use globs *)
• Use simple [ vs [[ (double brackets are safer)

References

• ShellCheck
• Google Shell Style Guide