How to Debug Bash Script: Simple Steps to Find Errors

To debug a bash script, run it with bash -x script.sh to see each command executed with its arguments. You can also add set -x inside the script to enable debugging from that point onward.

Why This Happens

Bash scripts often fail silently or behave unexpectedly because commands run without showing what is happening step-by-step. This makes it hard to see where the script goes wrong.

bash

#!/bin/bash

name=John
if [ "$name" = "John" ]
then
  echo "Hello, $name"
fi

The Fix

Enable debugging to see each command and its arguments as the script runs. Use bash -x script.sh from the terminal or add set -x inside the script before the code you want to debug.

bash

#!/bin/bash

set -x
name=John
if [ "$name" = "John" ]
then
  echo "Hello, $name"
fi

Output

+ name=John
+ '[' John = John ']'
+ echo 'Hello, John'
Hello, John

Prevention

Always quote variables in conditions to avoid errors from spaces or empty values. Use set -e to stop the script on errors and set -u to catch unset variables. Regularly run your script with bash -n to check syntax without executing.

Related Errors

Common errors include unquoted variables causing word splitting, missing fi for if blocks, and commands failing silently. Using set -x helps spot these quickly.

Key Takeaways

Use bash -x script.sh to see commands as they run for easy debugging.

Add set -x inside scripts to enable step-by-step tracing.

Quote variables in conditions to prevent unexpected errors.

Use set -e and set -u to catch errors early.

Run bash -n to check script syntax without running it.