Unix bash cheatsheet. Hope you find it useful 😉

unix-bash-cheatsheet.md

TOC

Basic

Shortcuts

File & Folder Manipulation

Directory & Navigation

Jobs

I/O Redirection

SSH

Network

User and Group

System

Storage

History

Other Shell Features

Basic

At start of line, indicates a comment.

#

Run cmd1, then if cmd1 successful run cmd2, otherwise skip.

cmd1 && cmd2

Run cmd1, then if cmd1 not successful run cmd2, otherwise skip.

cmd1 || cmd2

Do cmd1 and then cmd2.

cmd1; cmd2

Do cmd1, start cmd2 without waiting for cmd1 to finish.

cmd1 & cmd2

clears content on window (hide displayed lines)

clear

shows the manual for specified command

man

Shortcuts

halts the current command

Ctrl+C

stops the current command, resume with fg in the foreground or bg in the background

Ctrl+Z

Delete the current word / argument left of the cursor

Ctrl+W

cuts everything before the cursor

Ctrl+U

search previous typed commands

Ctrl+R

log out of current session

exit Ctrl+D

full window program

cmd+up

not full window program

cmd+down

undo

ctrl+_

swap two characters

ctrl+t

swap two words

ALT+t

prints last argument from previous command

ALT+.

expand glob/star

ctrl+x+*

move forward a word

ctrl+arrow

move forward a word

ALT+f

move backward a word

ALT+b

opens the command string in an editor so that you can edit it before execution

ctrl+x+ctrl+e

move to the opposite end of the line

ctrl+xx

cuts everything after the cursor

ctrl+k

pastes from the buffer

ctrl+y

clears screen and redisplay the line

CTRL+L

same as RETURN

CTRL+J

same as RETURN

CTRL+M

next line in command history

CTRL+N

same as RETURN, then displays next line in history file

CTRL+O

previous line in command history

CTRL+P

searches forward

CTRL+S

lists the possible filename completefions of the current word

CTRL+X

Move to beginning of line

Ctrl+A

Move to end of line

Ctrl+E

Directory & Navigation

create a new directory

mkdir

changes to home

cd

changes directory

cd

tells you where you currently are

pwd

Go to previous directory

cd -

delete directory dir

sudo rm -r dir

force remove directory dir *

sudo rm -rf dir

copy dir1 to dir2; create dir2 if it doesn't exist

cp -r dir1 dir2

Finds a file/directory

find filename dir Find files from root rirectory find / -name wordToFind* List files that match the reg. exp. from current folder find . -name wordToFInd

Shows the location of a file

whereis filename

Shows the location of a file if it is in your PATH

which filename

Jobs

Step 1, write in the terminal: at ENTER ex --> at 16:45 or at 13:43 7/23/11 (to be more precise) or after a certain delay: at now +5 minutes (hours, days, weeks, months, years) Step 2: ENTER repeat step 2 as many times you need Step 3: CTRL D to close input atq = show a list of jobs waiting to be executed atrm = delete a job n. ex (delete job #42) --> atrm 42 sleep = pause between commands with ";" you can chain commands, ex: touch file; rm file you can make a pause between commands (minutes, hours, dys) ex --> touch file; sleep 10; rm file <-- 10 seconds

execute a command regularly

crontab

modify the crontab

crontab -e

view current crontab

crontab -1

delete you crontab

crontab -r

Crontab syntax

<Day of week (0-6, 0 = Sunday)>

ex, create the file movies.txt every day at 15:47

47 15 * * * touch /home/bob/movies.txt

every minute

---

at 5:30 in the morning,from the 1st to 15th each month:

30 5 1-15 * *

at midnight on Mondays, Wednesdays and Thursdays:

0 0 * * 1,3,4

Execute programs in the background

Add a '&' at the end of a command

cp bigMovieFile.mp4 &

nohup: ignores the HUP signal when closing the console (process will still run if the terminal is closed)

nohup cp bigMovieFile.mp4

lists all jobs / what is running in the background (use with -l to see associated PID)

jobs

put a background process to foreground

fg (process 1), f%2 (process 2) f%3, ...

lists stopped or background jobs ; resume a stopped job in the background

bg

brings the most recent job in the foreground

fg

brings job to the foreground

fg To suspend a job, type CTRL+Z while it is running. You can also suspend a job with CTRL+Y. This is slightly different from CTRL+Z in that the process is only stopped when it attempts to read input from terminal. Of course, to interupt a job, type CTRL+C.

runs job in the background and prompts back the shell

myCommand &

brings most recently invoked background job

fg %+

brings second most recently invoked background job

fg %-

brings job number N

fg %N

brings job whose command begins with string

fg %string

brings job whose command contains string

fg %?string

removes the process from the list of jobs

disown <PID|JID>

waits until all background jobs have finished

wait

brings job n to the foreground

fg n

Scheduling a shutdown

wait 60 mins before starting the shutdown

sudo shutdown -P +60

shutdown at 1 AM

sudo shutdown -P 1:00

Cancel a pending shutdown

sudo shutdown -c

Run command at specific time

echo "ls -l" | at 07:00

I/O Redirection

Output of pgm is redirected to file.

pgm > file python hello.py > output.txt

Program pgm reads its input from file. (takes standard input from file)

pgm < file

feed foo.txt to stdin for python

python hello.py < foo.txt

Output of pgm is appended to file.

pgm >> file python hello.py >> output.txt

Output of pgm1 is piped into pgm2 as the input to pgm2.

pgm1 | pgm2

Standard input comes from here through next tag at start of line.

<< tag

Note that file descriptor 0 is normally standard input, 1 is standard output, and 2 is standard error output.

forces standard output to file even if noclobber is set

|file

forces output to file from file descriptor n even if noclobber is set

n>|file

uses file as both standard input and standard output

<> file

uses file as both input and output for file descriptor n

n<>file

Merge output from stream n with stream m.

n >& m

Merge input from stream n with stream m.

n <& m

duplicates standard output to file descriptor n

n>&

duplicates standard input from file descriptor n

n<&

directs standard output and standard error to file

&>file

closes the standard input

<&-

closes the standard output

&-

closes the ouput from file descriptor n

n>&-

closes the input from file descripor n

n<&-

stderr to (file)

python hello.py 2> error.log python hello.py 2>/dev/null

stderr to stdout

python hello.py 2>&1

stdout and stderr to (null)

python hello.py &>/dev/null

SSH

connects to host as user

ssh user@host

connects to host on specified port as user

ssh -p user@host

adds your ssh key to host for user to enable a keyed or passwordless login

ssh-copy-id user@host

Network

displays whois online

w

pings host and outputs results

ping

gets whois information for domain

whois

gets DNS information for domain

dig

reverses lookup host

dig -x

downloads file

wget

ping host and output results

ping host

continue a stopped download

wget -c file

User and Group

who you are logged in as

whoami

lets you change your password

passwd

displays information about user

finger Example: Display information about the user ch. Output will appear similar to the following: finger -p ch Login name: admin In real life: Computer Hope On since Feb 11 23:37:16 on pts/7 from domain.computerhope.com 28 seconds Idle Time Unread mail since Mon Feb 12 00:22:52 2001

lists your last logins

last

User and Group Quotas

Definition The user and group quotas provide the mechanisms by which the amount of space used by a single user or all users within a specific group can be limited to a value defined by the administrator. - Soft Limit − If the user exceeds the limit defined, there is a grace period that allows the user to free up some space. - Hard Limit − When the hard limit is reached, regardless of the grace period, no further files or blocks can be allocated.

Displays disk usage and limits for a user of group

quota

This is a quota editor. Users or Groups quota can be edited using this command

edquota

Scans a filesystem for disk usage, creates, checks and repairs quota files

quotacheck

This is a command line quota editor

setquota

This announces to the system that disk quotas should be enabled on one or more filesystems

quotaon

This announces to the system that disk quotas should be disabled for one or more filesystems

quotaoff

This prints a summary of the disc usage and quotas for the specified file systems

repquota

list all users available

who

root creates new user

sudo adduser bob

change a user's password

sudo passwd

Delete an account

sudo deluser

reate a new user group

addgroup friends

delete a user group

delgroup friends

add user to a group

usermod -g friends

change account name

usermod -g bob boby

add groups to a user without loosing the ones he's already in

usermod -aG friends bob

System

shows kernel information

uname -a

Memory & Process Management

cpu information

cat /proc/cpuinfo

memory information

cat /proc/meminfo

show memory and swap usage

free

process's from current user

ps -u yourusername

kill all processes with the name

killall

displays your currently active processes dinamically

top

prints process ID of the current shell

echo $$

prints process ID of the most recently invoked background job

echo $!

returns a list of all signals on the system, by name and number

kill -l

terminates process with specified PID

kill

selects all processes with a tty except session leaders

ps -a

executes a command when a signal is received by the script

trap cmd sig1 sig2

ignores that signals

trap "" sig1 sig2

resets the action taken when the signal is received to the default

trap - sig1 sig2

display your currently active processes

ps

List processes sorted

ps aux --sort -rss

display all running processes

top

select all processes

ps -e

kill process

killall UnResponsiveProg

Kill all processes matching the string "unresponsiveprog" (ignoring the difference between upper- ## lowercase letters)

killall -I unresponsiveprog

violent kill

kill -9

graphic representation of system load average (quit with CTRL C)

tload

View and Manage Processes

htop

Suspend and send to background

Ctrl + z Then bg

Get a process back to the foreground again

fg

Date & Time

shows the current date and time

date

shows current uptime

uptime

show this month's calendar

cal

show current uptime

uptime

List current day Events (calendar)

calendar

Output date

ex: 12-Mar-2004 date +%d-%b-%Y today=$(date +%d-%b-%Y) && echo $today If it's 9 am, then it will show 09 date “+%H”

Applications

show possible locations of app

whereis app

show which app will be run by default

which app

list all directories were installation script might added files

grep -P '("|/)\S+/\S+' setup.sh

run a program/app

sudo %program% sudo program -l

remove application

sudo apt-get remove <application_name>

When software is available in the repositories:

sudo apt-get install ex sudo apt-get install aptitude

downloaded package

sudo dpkg --install ex sudo dpkg --install megasync-xUbuntu_17.04_amd64.deb

If you download it from the Internets in .gz format

(or bz2) - “Compiling from source” Step 1, create a folder to place the file: mkdir /home/username/src <-- then cd to it Step 2, with 'ls' verify that the file is there (if not, mv ../file.tar.gz /home/username/src/) Step 3, decompress the file (if .zip: unzip ) Step 4, use 'ls', you should see a new directory Step 5, cd to the new directory Step 6.1, use ls to verify you have an INSTALL file, then: more INSTALL If you don't have an INSTALL file: Step 6.2, execute./configure <-- creates a makefile Step 6.2.1, run make <-- builds application binaries Step 6.2.2 : switch to root --> su Step 6.2.3 : make install <-- installs the software Step 7, read the readme file

Install from source

./configure make make install install a package (Debian) dpkg -i pkg.deb install a package (RPM) rpm -Uvh pkg.rpm

shutdown

sudo shutdown -h now

restart

sudo shutdown -r now

system update and upgrade

sudo apt-get update sudo apt-get -y upgrade sudo apt-get update && sudo apt-get upgrade

system cleanup

sudo apt-get autoclean sudo apt-get clean sudo apt-get autoremove sudo apt autoremove && sudo apt clean

When system freezes / stops working

Alt + F2, type xkill

firewall

To enable the firewall

sudo ufw enable

disable firewall

sudo ufw disable

Managing UFW via GUI

sudo apt install gufw

Prevent system from sleeping

systemd-inhibit

Return to normal policies after program execute

systemd-inhibit myProgram

Storage

Disk usage of folders, human readable

du -h

Disk usage of files & folders, Human readable

du -ah

Only show disc usage of folders

du -sh

shows what your disk quota is

quota -v

shows the disk usage of the files and directories in filename (du -s give only a total)

du du -s

show disk usage

df

show directory space usage

du The -h option makes the output easier to comprehend du -h /etc

(disk free) displays the disk space usage in kilobytes

df -k

History

Commands

Show history

history

Don’t execute expanded result immediately

shopt -s histverify

Expansions

Expand last parameter of most recent command

!$

Expand all parameters of most recent command

!*

Expand nth most recent command

!-n

Expand nth command in history

!n

Expand most recent invocation of command

!

Operations

Execute last command again

!! sudo !!

Replace first occurrence of to in most recent command

!!:s///

Replace all occurrences of to in most recent command

!!:gs///

Expand only basename from last parameter of most recent command

!$:t

Expand only directory from last parameter of most recent command

!$:h Note: !! and !$ can be replaced with any valid expansion.

Slices

Expand only nth token from most recent command (command is 0; first argument is 1)

!!:n

Expand first argument from most recent command

!^

Expand last token from most recent command

!$

Expand range of tokens from most recent command

!!:n-m

Expand nth token to last from most recent command

!!:n-$ !! can be replaced with any valid expansion i.e. !cat, !-2, !42, etc.

Easily search and use the commands that you had used in the past

ctrl+r search_term

Other Shell Features

Command-Line Processing Cycle.

The default order for command lookup is functions, followed by built-ins, with scripts and executables last. There are three built-ins that you can use to override this order: command, builtin and enable.

removes alias and function lookup. Only built-ins and commands found in the search path are executed

  command

looks up only built-in commands, ignoring functions and commands found in PATH

  builtin

enables and disables shell built-ins

  enable

takes arguments and run them through the command-line processing steps all over again

  eval

Create command alias

cd; nano .bash_profile

alias gentlenode='ssh admin@gentlenode.com -p 3404' # add your alias in .bash_profile Using alias to fix typos alias gerp=grep

To quickly go to a specific directory

cd; nano .bashrc

shopt -s cdable_vars export websites="/Users/mac/Documents/websites" source .bashrc cd websites