Linux | Shell Basics

Some of the most common Linux commands and their usages listed in the table below. Commands are sorted based on popularity whereas shortcuts are sorted alphabetically.

1. Basic Symbols

Symbol	Usage
(Slash) /	Used to denote following directories in the root tree /parent/childdirects to child folder inside the parent folder /parent/child/file1.txt directs to file1 text file inside the child folder, etc.
(Tilde) ~	Shortcut for the home directory - /home/username ~/Desktop means /home/username/Desktop
(Dot) .	Stands for the current directory you are located in Say you are in dir1/dir2/dir3 directory . represents dir1/dir2/dir3(current dir)
(2 Dots) ..	Stands for the parent directory (one directory up in the tree) .. represents dir1/dir2 directory (1 dir up) ../.. represents /dir1 directory (2 dir up)
(Dash) -	Stands for the recent directory located (or flags see below) - represents/dir1 (the most recent directory)
(Backward Slash) \	Used to skip characters if the name includes a space Either use \ or put inside a string to denote a new including a blank in the path name /dir1/new\ file or "/dir1/new file.txt"is used to denote the "new file.txt" text file in the dir1 folder
(Asterisk) *	Used as a wildcard during searches - matches one of more occurrences of any character, including no character ls -l a* lists all files whose name is starting with a ls -l A* lists different files as it is case sensitive
(Question Mark) ?	Used as a wildcard to represent an anonymous character ls e?dlists all 3-character files starts with e and d Possible results end, eid, etc.
(Brackets) [chars]	Used as a wildcard to represent a character between brackets ls l[aeoi]stlists all 4-character files starts with l ends with st if [aeoi] is one of the middle character. Possible results last, lost, list, etc.
<command> -options	Characters after a dash symbol following a command stands for options (flags) for that command to be executed Example: ls lists files in the current folder whereas ls -a lists all - including hidden ones Options (flags) for each command can be found in manual - use man <command> to see details
/home/username/.../file	Absolute path of a file from the root folder - always works!
../dir1/dir2/file.txt	Relative path to a file relative to the current directory Say you are in ~/Desktop/dir1/dir2/file.txt Absolute path of Desktop folder is: /home/username/Desktopor~/Desktop Relative path of Desktop to dir2 folder is: ../.. (.. directs to ~/Desktop/dir1)

2. Navigation Commands

Command	Usage
pwd	Prints working directory (absolute path)
cd <dir>	Changes directory to dir (folder) cd .moves to current dir (output ofpwd) cd ..moves 1 directory up cd ../..moves 2 directory up, etc. cd -prints and moves to the recent directory cd ~ moves back to home directory
ls <dir>	Lists all (excluding hidden) files in a given / current dir Use -a flag to list hidden files (.hiddenfile) Use -l to list files in the tabular (long) format Some flags can be combined - Example: ls -al
man <command>	Opens the user manual for the command
<command> --help	Opens the help page for the command
time <command>	Prints the time it takes to execute the command
history	Prints the last commands typed on the terminal
clear	Clears the terminal page (Ctrl+L)
cat	Concatenate - Multiple purpose
file <filename>	Displays the type of file given with filename
locate <file>	Locates (searches for) the file in the Linux system
shutdown <time>	Shuts down the system at a given time shutdown -h now - Shuts down the system immediately shutdown -r now - Reboot the system immediately
reboot	Stops and restarts the system
reset	Resets the terminal screen
exit	Logs out of terminal (Ctrl+D)
zip	Zipping files and folder - (password protected) zip -er namezipfile.zip filepath

3. Displaying System Information

Command	Usage
w	Displays the online user information
whoami	Displays the current username
date	Prints the full date with other details (Default): Day Month #Day hh:mm:ss TimeZone yyyy Example: Mon Jan 25 14:18:52 CST 2021
cal	Displays the monthly calendar
finger <user>	Displays user information
du	Shows directory space usage
df	Shows a report on the disk space usage
whereis <app>	Displays the location of the application
which <app>	Displays the default version of the app

4. Displaying File Contents

Command	Usage
echo <"string">	Prints the string
cat <file>	Prints the contents of the file
open <file>	Opens the file in the given path
less <file>	Displays the contents of the file Can navigate forward and backward through file
more <file>	Displays the contents of the given file Allows users to scroll up & down through pages
head # <text>	Displays the first # lines of the text file
tail # <text>	Displays the last # lines of the text file
grep <content> <text>	Searches (filters) for the content in the text file
sort <file>	Sorts the contents of the file
wc <file>	Displays the number of words (word count) in the file

5. Manipulating Files

Command	Usage
mkdir <name>	Makes directory with the given name
mv <file> <dir>	Moves the given file to the given directory Can be used to rename files ass well mv <file_name> <new_name>
rm <file>	Removes the given file - cannot be undone Cannot remove directories unless used with -r option rm -r <dir> - Recursively deletes all files in dir rm -rf <dir> - Does not ask for permit
rmdir <dir>	Removes the given directory if it is empty
touch <file1> <file2>	Creates a new file or files - file 1 (and file 2)
cp <file> <new_name>	Copies the given file with a given new name Can copy directories recursively with -r option cp -r <dir> <new_name>
cut <options> <file>	Cuts a specific part of the file
ln <source> <link>	Creates a physical / symbolic (-s option) links between files In order to remove the symbolic links use either: unlink <link> or rm <link>
file1 | file2	Redirects (STDOUT) output of file 1 to (STDIN) input of file 2
file1 > file2	Saves/redirects the (STDOUT) output of file 1 to file 2 Will overwrite the final output each time used
file1 >> file2	Appends (STDOUT) output of file 1 to file 2 - w/o overwriting
file1 2> file2	Redirects the (STDERR) error message of file 1 to file 2
command < file2	Passes the contents of the file 2 (STDIN) to a program

6. Terminal Shortcuts

Shortcut	Usage
CTRL + A or HOME	Moves the cursor to the beginning of the line
CTRL + B or ⇦	Moves the cursor back one character at a time
CTRL + C	Terminates the current running process
CTRL + D	Exits the bash shell - same with Exit command Also removes the character under the cursor while typing
CTRL + E or END	Moves the cursor to the ending of the line
CTRL + F or ⇨	Moves the cursor forward one character at a time
CTRL + K	Removes all the text from the cursor until the end of the line
CTRL + L	Clears the terminal (Moves the previous commands up)
CTRL + Q	Unfreezes the terminal (doesn't work in MacOS)
CTRL + S	Freezes the terminal (doesn't work in MacOS)
CTRL + X + Backspace	Removes all the text from the cursor to the beginning Doesn't work in some Macs as there is no backspace Option + Delete in MacOS
CTRL + Z	Pauses the current running process
CTRL +⇦ or ALT + B	Moves the cursor back one word at a time
CTRL +⇦ or ALT + C	Moves the cursor forward one word at a time
TAB	Use TABto autocomplete the path/file names
⇧ | ⇩	Use arrows to display previously typed commands

References:

0) https://ubuntu.com/tutorials/command-line-for-beginners#1-overview

1) The Linux Command Line by William Shotts

2) https://www.pluralsight.com/guides/beginner-linux-navigation-manual

3) https://ryanstutorials.net/linuxtutorial/

4) https://maker.pro/linux/tutorial/basic-linux-commands-for-beginners

5) https://www.tecmint.com/linux-command-line-bash-shortcut-keys/