Linux Shell Scripting Best Practices For Writing Scripts

Shell scripting best practices

A shell script is rarely a “one-off” activity in the DevOps world. Colleagues will read it, incorporate it into CI/CD pipelines, and compare it to production infrastructure. Writing a script that “just works” is insufficient; it needs to be professional, safe, and maintainable.

The following lists the essential procedures that set production-grade automation apart from a script created for fun.

Writing Readable Scripts

Readability is about reducing the “cognitive load” for the next person (or your future self) who reads the code.

• Descriptive Naming: Avoid variables like f or temp. Use SOURCE_FILE or BACKUP_TIMESTAMP.
• Modularize with Functions: If a block of code performs a specific task (like authenticating to an API), wrap it in a function. This makes the main logic of the script read like a story.
• Consistency: Use a consistent indentation style (usually 2 or 4 spaces, never mix tabs and spaces).
• Long Options: In scripts, use the long version of command flags (e.g., curl --request instead of curl -X). It makes the code self-documenting.

Also Read About Shell Script Compiler SHC: Features, Usage, And Examples

Documentation and Commenting

Comments should explain why something is being done, not what the code is doing (the code should be clear enough to explain the “what”).

• Header Ceremony: Every script should start with a header block:

#!/bin/bash
# Purpose: Automates weekly database backups to S3.
# Author: DevOps Team
# Dependencies: aws-cli, jq

• Usage Function: Always include a -h or --help flag that prints instructions on how to use the script, including required arguments and examples.
• Inline Complexity: If you use a complex Regex or a dense awk command, add a comment above it explaining the logic.

Version Control Best Practices

Scripts are code and should be respected like application source.

• Do not combine 10 fixes into one Git commit. Logical changes must be committed individually.
• Linting: ShellCheck before committing. It is the industry standard for bug, quotation, and non-portable syntax detection.
• Environment Variables: Never version control passwords or API credentials. Git ignores.env files, therefore use HashiCorp Vault or AWS Secrets Manager.

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Production Safety and Error Handling

Production scripts must be “defensive.” They should assume things will go wrong and fail gracefully.

The Strict Mode Header:

Bash

set -euo pipefail

• -e: Exit on error.
• -u: Exit on unset variables.
• -o pipefail: Catch errors hidden inside pipes.

Dry Run Mode: Implement a --dry-run flag that prints the commands it would execute without actually changing the system.

Atomic Operations: If your script moves files, ensure it verifies the move was successful before deleting the source.

Testing Your Scripts

Testing shell scripts is difficult but necessary for CI/CD dependability.

• Manually test on a production-like “staging” or “vagrant” VM.
• Mocking: Use “mocks” or “stubs” to test a cloud API script without spending money or changing infrastructure.
• Automated Frameworks: Bats-core (Bash Automated Testing System) is one testing framework that may be useful for sophisticated logic. As with Python or Java, it enables you to create test cases for your scripts.

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