Scripting and Task Scheduling Flashcards

What does the `at` command do?

Answer: Runs a command at a specific future time once

The `at` command schedules a command or script to run once at a specified future time, unlike cron which runs jobs repeatedly.

Which command in bash reads user input and stores it in variable `NAME`?

Answer: read NAME

The `read` built-in command reads a line from standard input and assigns it to the specified variable.

What does `2>&1` do in a bash command?

Answer: Redirects stderr to stdout

`2>&1` redirects file descriptor 2 (stderr) to wherever file descriptor 1 (stdout) currently points.

Which bash construct tests if a variable `$FILE` exists as a regular file?

Answer: if [ -f $FILE ]

The `-f` test operator returns true if the specified path exists and is a regular file.

What does the `#!/usr/bin/env bash` shebang offer over `#!/bin/bash`?

Answer: Portability — uses the first `bash` found in PATH

`#!/usr/bin/env bash` uses `env` to locate `bash` in the PATH, making the script more portable across systems where bash may not be at `/bin/bash`.

Which directory stores system-wide cron jobs organized by frequency?

Answer: /etc/cron.hourly/, /etc/cron.daily/, etc.

Scripts placed in `/etc/cron.hourly/`, `/etc/cron.daily/`, `/etc/cron.weekly/`, and `/etc/cron.monthly/` are run at the respective intervals by `run-parts`.