Shell Scripting & Automation Flashcards

Which construct is used in bash to iterate over a list of files matching a glob pattern?

Answer: for f in /etc/*.conf; do ...; done

The for loop with a glob pattern expands the pattern and iterates over each matching file.

What does the `set -e` option do in a bash script?

Answer: Exits the script immediately if any command returns a non-zero exit status

`set -e` causes the shell to exit immediately when a command exits with a non-zero status.

Which command reads a line of input from the user and stores it in a variable named REPLY?

Answer: read

The `read` command without a variable name stores input in the default variable $REPLY.

In a bash script, what is the value of `$?` after a command succeeds?

Answer: 0

A zero exit status ($?) indicates that the previous command completed successfully.

What does `trap 'rm -f /tmp/lockfile' EXIT` accomplish in a script?

Answer: Removes the lockfile when the script exits for any reason

The `trap ... EXIT` command registers a cleanup handler that runs whenever the script exits, including on error or signal.

Which bash feature allows you to test if a variable is set and non-empty using `[[ -n $VAR ]]`?

Answer: String length test

The `-n` flag inside `[[ ]]` tests whether the string length is non-zero, i.e., the variable is set and non-empty.

What output does `echo ${#MYVAR}` produce if MYVAR='hello'?

Answer: 5

The `${#var}` parameter expansion returns the length of the string stored in the variable.