Basics

at

Install with: 1sudo apt install at Enable the daemon service with: 1sudo systemctl enable --now atd Then jobs can be specified with absolute time, such as: 1at 16:20 1at noon 1at midnight 1at teatime Type in your command, e.g.: 1touch /tmp/$FILE.txt The jobs can also be specified relative to the current time: 1at now …

Basics

6 min read · basics

You need about a dozen commands to move around Linux. After that, you look up the rest as you go. Don't worry about understanding any of it, just type it in and the habit forms pretty quickly. You start in a dark room. You want to know where you are by printing out your working 'directory' (i.e. 'location'): 1pwd Have …

clock

1 min read · basics time

Show system time: 1date Show hardware time: 1sudo hwclock -r Change system time to match hardware time: 1sudo hwclock --hctosys Change hardware time to match system time: 1sudo hwclock --systohc Manually set the hardware time to a specified date: 1sudo hwclock --set --date="8/25/19 13:30:00" Normal Date 1date +%d/%m/%y …

column

1 min read · basics format json

Put output into column. 1du -h /etc/* | column Reformat file with an explicit separator (-s): 1column -ts: /etc/passwd Give columns names (-N), so you can hide some (-H): 1column -ts: -N User,PW,UID,GID,Description,Home,shell -H PW,GID /etc/passwd Reorder with -O (unspecified items remain): 1column -ts: -N …

conditionals

1 min read · basics

If statements Test statement equality as so: 1 2read t1 3read t2 4if test $t1 != $t2; then 5 echo 'variables do not match' 6else 7 echo 'variables match' 8fi 9exit 0 Case Structure These deal with multiple states rather than forking conditions. Example: 1 2#!/bin/bash 3 4# Simple case demonstration 5 6echo "What's your …

cron

2 min read · basics time

Cronie The cronie program is also known as crond. Install 1sudo apt search -n ^cron Once installed, search for the service name, and start it. 1sudo systemctl list-unit-files | grep cron 2sudo systemctl enable --now $NAME Usage Show your current crontab: 1crontab -l You can put this in a file and edit it: 1crontab -l > …

eval

1 min read · basics

Compose a statement for execution. 1x='echo $y' 2echo $x 3y=dragon 4eval "$x" The results remain in the current shell, unlike sub-shells. 1b=basilisk 2sh -c 'echo $b' 3eval "g=goblin" 4echo $g

hard links

1 min read · basics links

A hard link is one file which exists in multiple locations. Each file has an ID, which is kept on the hard disk's partition. Each hard link has the same ID, because they are the same file. This ID is called the 'inode'. Create a file, and a hard link: 1fortune > $file_1 2mkdir -p x/y/z/ 3ln $file_1 x/y/z/$file_2 Have a …

kill

2 min read · basics

If you want to kill a program in a graphical environment, open a terminal and type: Graphical Programs 1xkill Then click on the application which you want to kill. All Programs To kill a program, find it with: 1pgrep discord This will give you the UUID, e.g. 19643. Kill the program with: 1kill 19643 Types of Kill To …