ITLSA1-22 - Linux-Based Operating Systems: Week 6 Automation

This set of flashcards covers Linux automation tools including cron, at, anacron, and comprehensive Bash scripting concepts including syntax, operators, and functions based on the Week 6 lecture.

crond

A daemon in Linux that reads configuration files and manages the execution of scheduled tasks.

/etc/crontab

The configuration file used for system-wide scheduled jobs in Linux.

crontab -l

A command used to display the current user’s list of scheduled jobs.

crontab -e

A command used to edit the current user’s crontab file.

crontab -r

A command used to remove all of the current user’s scheduled jobs.

Crontab Entry Syntax

The format used to schedule jobs, consisting of: minute $(0-59)$, hour $(0-23)$, day of month $(1-31)$, month $(1-12)$, and day of week $(0-6 \text{ or } 0,7)$.

*/x

A special character in crontab syntax used to define an interval, such as every seven minutes ($*/7$).

@reboot

A modern cron shortcut that schedules a command to run once immediately after the system reboots.

at

A utility for scheduling one-time tasks at a specific time, requiring the atd daemon to be active.

atq

A command used to list all pending tasks scheduled via the at utility.

anacron

A utility designed for systems that do not run $24/7$, ensuring scheduled jobs run even if the system was powered off during the intended time.

Vixie Cron

A version of cron introduced in $1993$ that added security and logging enhancements.

Brian Fox

The individual who created Bash in $1989$ as part of the GNU Project.

$$((...))$$

The syntax used for performing in-process integer arithmetic within a Bash script.

#!\text{/bin/bash}

The Shebang line, which indicates that the script should be interpreted and executed by the Bash shell.

read

A Bash command used to capture user input from the keyboard and assign it to a variable.

$$[ "\text{VAR1}" == "\text{VAR2}" ]$$

The standard conditional syntax in Bash used to compare strings or values.

$$-ne$$

A numeric comparison operator in Bash used to evaluate if two values are 'not equal.'

$$-ge$$

A numeric comparison operator in Bash used to evaluate if a value is 'greater than or equal to' another.

break

A command used within loops to exit the loop entirely.

continue

A command used within loops to skip the current iteration and move to the next one.

$$@$$

A command line argument variable that represents all arguments passed to a Bash script.

$$0$$

A special Bash variable that stores the name of the script being executed.

$

The syntax identified in the provided transcript for representing the number of command line arguments (standardly denoted as #).

local

A keyword used in Bash functions to define a variable whose scope is restricted to that function.

$$?$$

A variable that holds the return value or exit status of the most recently executed command or function.

$$-e$$

A file check operator used to determine if a specific file or directory exists.

$$-d$$

A file check operator used to determine if a specific path exists and is a directory.

$$-f$$

A file check operator used to determine if a specific path exists and is a regular file.

Bourne Family

A shell family characterized by shells such as sh, ash, zsh, ksh, and bash.