Error logging patterns in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of error logging in bash scripts?

Error logging helps capture and record errors during script execution. It makes troubleshooting easier by showing what went wrong and where.

beginner

How do you redirect error messages to a log file in bash?

Use the syntax command > logfile 2>&1. This sends both standard output and error output to the log file.

intermediate

What does 2>&1 mean in bash redirection?

It means redirect standard error (file descriptor 2) to the same place as standard output (file descriptor 1).

intermediate

Why use a function for error logging in bash scripts?

A function centralizes error handling. It makes the script cleaner and easier to maintain by reusing the same logging format and actions.

intermediate

Show a simple bash function that logs errors with timestamps.

Example:

log_error() {
  echo "$(date '+%Y-%m-%d %H:%M:%S') ERROR: $1" >&2
}

This prints the error message with a timestamp to standard error.

Which bash redirection sends both output and errors to the same file?

A command > logfile 2>&1

B command 2> logfile

C command > logfile

D command 1> logfile 1>&2

Option A redirects standard output to logfile and then redirects standard error (2) to the same place as standard output (1).

What does the following bash code do? exec 2>error.log

A Redirects standard output to error.log

B Redirects all future error messages to error.log

C Deletes error.log

D Runs error.log as a command

The exec command changes the file descriptor 2 (standard error) to write into error.log for the rest of the script.

Why is it helpful to include timestamps in error logs?

A To confuse users

B To make logs bigger

C To speed up the script

D To know when errors happened

Timestamps help track when errors occurred, which is useful for debugging and correlating events.

Which of these is a good practice for error logging in bash scripts?

A Logging errors with clear messages and timestamps

B Ignoring errors silently

C Printing errors only to the screen without saving

D Using random file names for logs

Clear messages with timestamps make error logs useful for troubleshooting.

What does this function do?

log_error() {
  echo "ERROR: $1" >&2
}

A Deletes error messages

B Prints an error message to standard output

C Prints an error message to standard error

D Logs errors to a file automatically

The function prints the message passed as $1 to standard error using >&2.

Explain how to redirect error messages to a log file in a bash script and why it is useful.

Think about how to capture errors and save them for later review.

Describe how you would create a reusable error logging function in bash and what features it should have.

Consider how to make error messages clear and easy to find.