basics.md

Linux

Linux Productivity Tools

Input / output

0 = STDIN 1 = STDOUT 2 = STDERR

Write to standard output

cat > output.txt
cat 1> output.txt

Append to standard output

cat >> output.txt

Redirection

Redirection of STDOUT breaks pipelines

cat -k asdf 2> error.txt
cat -k asdf 2>> error.txt

Read file and redirect to output

cat 0< index.html 1> index.php
cat < index.html > index.php

Piping output

Piping connects STDOUT of one command to the STDIN of another

date | cut -d " " -f 1
date | cut -d " " -f 2 > ~/month.txt

Tee

To save a data 'snapshot' without breaking pipelines

date | tee ~/date.txt | cut -d " " -f 1 > today.txt

Xargs

To pipe if command does not accept STDIN

date | cut -d " " -f 1 | xargs echo
cat files_to_delete.txt | xargs rm

File system

Directory	Purpose
**/ **	Root
**/bin **	Common user command binaries ex. date, cat, cal
**/boot **	Bootable linux kernel and bootloader config files
**/dev **	Devices ex. tty=terminal, sd or hd = hard disks, ram etc.
**/home **	Home directories for regular users
**/media **	Removable media mounting directory ex. usb
**/lib **	Libraries needed by applications in /bin and /sbin to boot the system
**/mnt **	External devices mounting directory (supressed by /media)
**/misc **	Used to sometimes automout filesystems on request
**/opt **	Directory structure used to store additional software
**/proc **	Information about system resources
**/root **	Home folder for the root user
**/sbin **	Administrative command binaries for super user
**/tmp **	Temporary files used by running apps
**/usr **	Users files that don't change after installation
**/var **	Variable data ex. logs
**/etc **	Administrative config files

Creating files with brace expansion

mkdir {jan, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec}_{2020, 2021}
touch file_{a..z}_{0..9}.txt

Wildcards

• * matches anything
• ? matches anything but just for one place
• [] matches just one place but allow to specify regular expression

ls file*.txt
ls file?.txt
ls file[0-9].txt