Terminal commands cheat sheet

Jul 10, 2024

Basics

Commands are case sensitive.
Pressing the Tab key helps with autocompletion.
/ (slash): directory separator.
~ (tilde): home directory.
| (pipe): to chain two commands together (if the first command has an error it doesn't go for the second.
Command options can be combined. (ls -l -a = ls -la)
Use quotes ("my notes.txt" or 'my notes.txt') or a backslash (my\ notes.txt) to escape spaces.
The clear command, or pressing Ctrl + L, clears the terminal screen of all previous commands and outputs, giving you a fresh view.

Commands

!!	Repeat the previous command
↑↓ ([Ctrl] + p, [Ctrl] + n)	Search previous commands
[Ctrl] + g	Cancel the search
history	Display the shell history
export HISTSIZE=number	Controll the number of command to retain in history (see the default: echo $HISTSIZE)
command -h	Ask the command for help
which command	Location (full path) of the command
man command	Manual of the command
[space]	Next page
q	Quit

Navigating

.	Current directory
..	Parent directory
pwd	Desplay present working directory
cd	Change directory to default directory (home)
cd-	Change to the previous directory (to see the previous directory: echo $OLDPWD)
cd directory	Change directory to dir

Creating and Removing

mkdir name	Create a directory
mkdir -p parent_name/child_name	Create a parent with a child
rmdir name	remove a directory (which has no contents)
rm -rf name	Recursively remove a directory (which has contents)
touch name	Create a file (if not exist)
rm name	Remove a file

Listing and Sorting

ls	List current directory contents (in alphabetic order)
ls directory	List dir contents
ls -a	List all contents (including hidden files)
ls -l	List contents in a long format
ls -t	List by time
ls -r	Reverse list order
ls -R	List with childs (tree: display visualized)
ls -F	Reveal file types (/: directory, @: link, *: executable)
ls --color	Colorize output (done by default in some distros)
sort file_name	Sort the contents of a text file, line by line (by alphabet)
sort -r file_name	Sort in reverse order
sort -u file_name	Sort unique (doesn't show repeated text)

Moving and copying

mv source destination	Move a file/directory (if destination doesn't exist, source will be rename)
cp -r source destination	Copy a file/directory

Reading a file

cat file_name	Display the contents of the file
head file_name	Display 10 line of the top (-<number> for more or less lines)
tail file_name	Display 10 line of the bottom (-<number> for more or less lines)
tail -f file_name	Real time viewing (for log files)

Writing a file

nano file_name	Edit the contents of the file
[^]+[x]	Exit
[^]+[o]	Save
[^]+[g]	Get help

Search in a file

grep pattern file_name	Display the lines matching a pattern
-i	Ignore upper case and lower case
-c	Precede output with line numbers
-v	Invert match (prints lines that don't match)

Compairing files

diff file1 file2	Compare two files (or directories contents)
sdiff file1 file2	Compare two files side by side
vimdiff file1 file2	Highlight differences using vim
[ctr]+[ww]	Move between windows
[:]+[qa]	Close all

Compressing files

du -h	Display file size (human readable)
tar cf name.tar file1 file2	Archive the files
tar czf name.tar file1 file2	Archive the files with compression
tar tf name.tar	Show the contents
tar tvf name.tar	Show the contents in long format
tar xf name.tar	Extract the archive
gzip name.gz	Zip the files
gunzip name.gz	Unzip the files

I/O

>	Redirect outputs to a file - overwrites the contents if the file exist (ls -l > file.txt)
>>	Redirect outputs to a file - appends the contents if the file exist
<	Redirect inputs from a file to a command (sort < file.txt)

Whildcards

*	Match zero or more characters (.txt - a - a*txt)
?	Match exactly one character (?.txt - a? - a?txt)
[]	Match any of the characters included between the brackets (ca[nt]* -> can, cat, catch)
[!]	Match any of the characters NOT included between the brackets
[a-g]	Get range (it can include numbers -> [2-8])
[[:alpha:]]	Match alphabetic letters (others: digit, alnum, lower, upper, space)

َUsers and Groups

whoami	Display current user
~ + [tab]	Display all users
sudo su	Switch to the superuser
sudo command	Run a command as superuser
sudo -s username	Change user
sudo -u username command	Run a command as another user
groups	displays all groups
groups username	Display groups of a user
chgrp group_name file_name	Change groups of a file
chmod [ugoa\|+-=\|rwx] file_name	Change groups of a file

Connecting and Transfering

ssh user@host	Connect to host as user
ssh -p port user@host	Connect using special port
sftp user@host	Connect to host for transfering a file
pdw	Server pwd
lpdw	Local pwd
put file_name	Transfer the file
quit	Disconnect the session
scp filename user@host:path	Transfer a file without a session

Environment Variable

Environment Variables are key-value pairs configured outside your source code so that each value can change depending on the Environment. Your source code can read these values to change behavior during the Build Step or during Function execution.

printenv	List environment variables
export [key]="[value]"	Create/Update environment variables (TZ="US/Pacific")
echo $[key]	View an environment variable
unset [key]	Remove an environment variable
echo 'export [key]="[value]"' >> ~/.bash_profile	Persist env changes (they will not be deleted when exiting)

Aliases

Shortcuts: alias ll='ls -l'
Fix typos: alias grpe='grep'
Change behave like another os: alias cls='clear'

alias	List aliases
alias [key]="[value]"	Create an alias (TZ="US/Pacific")
unalias [key]	Remove an alias
echo 'alias [name]="[value]"' >> ~/.bash_profile	Persist aliases (they will not be deleted when exiting)

Cron Jobs

crontab -l	List cron jobs
crontab file_name	Install crontabs from a file
crontab -r	Remove all cron jobs

Daily: 0 0 * * *
Weekly: 0 0 * * 0
Monthly: 0 0 1 * *
Annually: 0 0 1 1 *
run every Monday at 7 pm and send output to a log file: 0 7 * * 1 /root/backupdb > /tmp/db.log 2>&1
run every 15 minutes: 0,15,30,45 * * * * or */15 * * * *