Scripting and Task Scheduling Flashcards

What `bash` option makes a script exit immediately if any command fails?

Answer: set -e

`set -e` (errexit) causes the script to exit immediately if any command returns a non-zero exit status.

Which command lists pending `at` jobs?

Answer: Both A and B

Both `atq` and `at -l` list pending at jobs; `atq` is a traditional shorthand while `at -l` is the long form.

What does `${#VAR}` return in a bash script?

Answer: Length of the string in VAR

`${#VAR}` is bash parameter expansion that returns the number of characters in the string value of VAR.

Which `for` loop syntax in bash iterates over a list of numbers 1 through 5?

Answer: for i in {1..5}; do

Bash brace expansion `{1..5}` generates the sequence 1 2 3 4 5, which the `for` loop iterates over.

What is the purpose of the `/etc/cron.deny` file?

Answer: Lists users who are NOT allowed to use crontab

Users listed in `/etc/cron.deny` are not permitted to create or modify crontab entries with the `crontab` command.

Which systemd command shows the output (logs) of a timer-triggered service?

Answer: journalctl -u myservice.service

`journalctl -u myservice.service` shows the systemd journal logs for the service unit that the timer activates.