What does 'set -e' mean in a Bash script?

set -e is a Bash option that instructs the shell to exit immediately if any command returns a non-zero status. In other words, if any command in your script fails, the script stops rather than continuing with subsequent commands.

This behavior is useful for:

1. Detecting Errors Early: By halting on the first failure, you avoid executing dependent operations that rely on a successful outcome of earlier steps.
2. Safer Scripts: Helps prevent silently ignoring errors that might lead to corrupted data, incomplete installations, or misconfigurations.

Example

#!/usr/bin/env bash
set -e

echo "Starting script..."
some_command_that_might_fail
echo "If the above command fails, this line won't be executed."

• If some_command_that_might_fail returns a non-zero status, the script exits immediately, and you won’t see the “this line won’t be executed” message.

Cautions

• Exceptions: Certain commands like if statements, loops, and logical operators (||, &&) can override the “fail on error” behavior depending on how they’re used.
• Traps or Cleanup: If you need to perform cleanup even on failure, consider using traps or conditional logic around critical sections.

Further Learning

For a deeper understanding of Unix shell scripting and better coding patterns, consider these courses from DesignGurus.io:

1. Grokking Data Structures & Algorithms for Coding Interviews – Strengthen your algorithmic thinking, ensuring you write efficient scripts and handle edge cases gracefully.

2. Grokking the Coding Interview: Patterns for Coding Questions – Learn the most common coding patterns tested at top tech companies, boosting your problem-solving skills in both interviews and real-world development.