Bash — Debugging

Set options

#!/bin/bash
set -x  # Print commands before execution
set -e  # Exit on error
set -u  # Error on undefined variables
set -o pipefail  # Catch pipe errors

Trace execution

#!/bin/bash
set -x
# Commands will be printed before execution
echo "This will be traced"

Trap for debugging

#!/bin/bash
trap 'echo "Error on line $LINENO"' ERR
trap 'echo "Script interrupted"' INT

Debug functions

debug() {
    [[ "${DEBUG:-false}" == "true" ]] && echo "[DEBUG] $*"
}

DEBUG=true debug "Variable: $var"

Common errors

# Unquoted variables
# Bad:  rm $file
# Good: rm "$file"

# Missing shebang
# Always start with #!/bin/bash

# Unused variables
# Use set -u to catch

Mini Practice

Write Bash code that:

1. Uses set -x for tracing
2. Sets up trap for debugging
3. Creates a debug function
4. Demonstrates common error patterns

Up Next

In the next lesson, you'll learn about Security — writing secure scripts.