Linux Commands

This is a list of the most commonly used Linux commands and their usage.

1. ls

Syntax : ls [options] [directory]

Usage : ls is used to list the contents of a directory. It can be used to list the contents of the current directory or any other directory.

Commands Used:

ls # list the contents of the current directory
ls -l # list the contents of the current directory in long format
ls -a # list the contents of the current directory including hidden files
ls -la # list the contents of the current directory in long format including hidden files

2. cd

Syntax : cd [directory]

Usage : cd is used to change the current working directory. It can be used to change the current working directory to the home directory or any other directory.

Commands Used:

cd # change the current working directory to the home directory
cd / # change the current working directory to the root directory
cd /home # change the current working directory to the home directory
cd Documents # change the current working directory to the Documents directory of the user
cd .. # change the current working directory to the parent directory
cd ../.. # change the current working directory to the grandparent directory

3. grep

Syntax : grep [options] pattern [file]

Usage : grep is used to search for a pattern in a file. It can be used to search for a pattern in a file or in the output of a command.

Commands Used:

=> replace pattern like: "abc" and file like: note.txt

grep pattern file # search for a pattern in a file
grep pattern file1 file2 # search for a pattern in multiple files
grep pattern file1 file2 | grep pattern # search for a pattern in multiple files and then search for another pattern in the output of the first grep command
grep -i pattern file # search for a pattern in a file ignoring the case
grep -v pattern file # search for a pattern in a file and print all the lines that do not match the pattern
grep -c pattern file # search for a pattern in a file and print the number of lines that match the pattern
grep -n pattern file # search for a pattern in a file and print the line numbers of the lines that match the pattern
grep -l pattern file1 file2 # search for a pattern in multiple files and print the names of the files that contain the pattern
grep -r pattern directory # search for a pattern in all the files in a directory and its subdirectories
grep -w pattern file # search for a pattern in a file and print only the lines that contain the pattern as a word
grep -x pattern file # search for a pattern in a file and print only the lines that contain the pattern as a line
grep -E pattern file # search for a pattern in a file using extended regular expressions
grep -F pattern file # search for a pattern in a file using fixed strings
grep -A n pattern file # search for a pattern in a file and print n lines of context after the matching lines
grep -B n pattern file # search for a pattern in a file and print n lines of context before the matching lines
grep -C n pattern file # search for a pattern in a file and print n lines of context before and after the matching lines

4. su/ sudo

Syntax : su [options] [username] or sudo [options] command

Usage : su is used to switch to another user. It can be used to switch to the root user or any other user.

sudo is used to execute a command as another user. It can be used to execute a command as the root user or any other user.

replace username like: sam

su # switch to the root user
su - # switch to the root user and start a new shell
su - username # switch to the user with the username and start a new shell
su username # switch to the user with the username

sudo command # execute a command as the root user
sudo -u username command # execute a command as the user with the username

5. pwd

Syntax : pwd

Usage: pwd is used to print the current working directory.

Commands Used:

pwd # print the current working directory

6. mv

Syntax : mv [options] source destination

Usage : mv is used to move or rename a file or directory. It can be used to move or rename a file or directory in the same directory or in a different directory.

Commands Used:

mv file1 file2 # rename the file1 to file2
mv file1 file2 directory # move the file1 to the directory and rename it to file2
mv file1 directory # move the file1 to the directory

7. cp

Syntax : cp [options] source destination

Usage : cp is used to copy a file or directory. It can be used to copy a file or directory in the same directory or in a different directory.

Commands Used:

cp file1 file2 # copy the file1 to file2
cp file1 file2 directory # copy the file1 to the directory and rename it to file2
cp file1 directory # copy the file1 to the directory

8. rm

Syntax : rm [options] file

Usage : rm is used to remove a file or directory. It can be used to remove a file or directory in the same directory or in a different directory.

Commands Used:

rm file # remove the file
rm -r directory # remove the directory and all its contents
rm -f file # remove the file without prompting for confirmation
rm -rf directory # remove the directory and all its contents without prompting for confirmation

9. mkdir

Syntax : mkdir [options] directory

Usage : mkdir is used to create a directory.

Commands Used:

mkdir directory # create the directory

10. rmdir

Syntax : rmdir [options] directory

Usage : rmdir is used to remove a directory.

Commands Used:

rmdir directory # remove the directory

11. chmod

Syntax : chmod [options] permissions file

Usage : chmod is used to change the permissions of a file or directory.

Commands Used:

chmod u+x file # add the execute permission to the user
chmod u-x file # remove the execute permission from the user
chmod u=rwx file # set the permissions of the user to read, write and execute
chmod u=rw file # set the permissions of the user to read and write
chmod u=r file # set the permissions of the user to read
chmod u=w file # set the permissions of the user to write
chmod u=x file # set the permissions of the user to execute
chmod u= file # remove all the permissions of the user
chmod g+x file # add the execute permission to the group

12. cat

Syntax : cat [options] file1 file2

Usage : cat is used to concatenate files and print on the standard output.

Commands Used:

cat file1 file2 # print the contents of file1 and file2
cat file1 file2 > file3 # print the contents of file1 and file2 and save it to file3
cat file1 file2 >> file3 # print the contents of file1 and file2 and append it to file3

13. chown

Syntax : chown [options] username file

Usage : chown is used to change the owner of a file or directory.

Commands Used:

chown username file # change the owner of the file to the user with the username
chown username:group file # change the owner of the file to the user with the username and the group of the file to the group with the groupname

14. echo

Syntax : echo [options] string

Usage : echo is used to display a line of text/string.

Commands Used:

echo "Hello World" # display the string Hello World

15. wc

Syntax : wc [options] file

Usage : wc is used to count the number of lines, words, and bytes in a file.

Commands Used:

wc file # count the number of lines, words, and bytes in the file
wc -l file # count the number of lines in the file
wc -w file # count the number of words in the file
wc -c file # count the number of bytes in the file

16. man

Syntax : man [options] command

Usage : man is used to display the user manual of any command that we can run on the terminal.

Commands Used:

It provides a detailed view of the command which includes NAME, SYNOPSIS, DESCRIPTION, OPTIONS, EXIT STATUS, RETURN VALUES, ERRORS, FILES, VERSIONS, EXAMPLES, AUTHORS and SEE ALSO.

17. history

Syntax : history [options]

Usage : history is used to print the history of commands.

Commands Used:

history # print the history of commands
history | grep command # print the history of commands that contain the command

18. clear

Syntax : clear

Usage : clear is used to clear the terminal screen.

Commands Used:

clear # clear the terminal screen

19. touch

Syntax : touch [options] file

Usage : touch is used to create a file.

Commands Used:

touch file # create the file

20. locate

Syntax : locate [options] file

Usage : locate is used to find the location of a file or directory.

Commands Used:

locate file # find the location of the file

21. netstat

Syntax : netstat [options]

Usage : netstat is used to display network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.

Commands Used:

netstat # display network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
netstat -t # display TCP connections
netstat -u # display UDP connections
netstat -l # display listening sockets

22. df

Syntax : df [options]

Usage : df is used to display the amount of disk space available on the file system.

Commands Used:

df # display the amount of disk space available on the file system
df -h # display the amount of disk space available on the file system in human readable format

23. du

Syntax : du [options]

Usage : du is used to estimate file space usage.

Commands Used:

du # estimate file space usage
du -h # estimate file space usage in human readable format

24. uname

Syntax : uname [options]

Usage : uname is used to print certain system information.

Commands Used:

uname # print certain system information
uname -a # print all system information

25. passwd

Syntax : passwd [options]

Usage : passwd is used to change the password of a user.

Commands Used:

passwd # change the password of the current user
passwd username # change the password of the user with the username

26. useradd

Syntax : useradd [options] username

Usage : useradd is used to add a new user to the system.

Commands Used:

useradd username # add a new user with the username to the system

27. userdel

Syntax : userdel [options] username

Usage : userdel is used to delete a user from the system.

Commands Used:

userdel username # delete the user with the username from the system

28. apt-get

Syntax : apt-get [options]

Usage : apt-get is used to install, remove, and update software packages on Debian based systems.

Commands Used:

=> replace "package" with the name of the package you want to install, remove, or update

eg: "vim", "git"

Note: You may need to add sudo before the commands.

apt-get install package # install the package
apt-get remove package # remove the package
apt-get update # update the package list
apt-get upgrade # upgrade the packages

29. ping

Syntax : ping [options] hostname

Usage : ping is used to test the reachability of a host on an Internet Protocol (IP) network.

Commands Used:

hostname is the name of the host to be pinged eg: "www.google.com"

ping hostname # test the reachability of the host with the hostname

30. find

Syntax : find [options] path

Usage : find is used to search for files in a directory hierarchy.

Commands Used:

find path -name "file" # search for the file in the path
find path -type f # search for the files in the path
find path -type d # search for the directories in the path

31. head

Syntax : head [options] file

Usage : head is used to output the first part of files.

Commands Used:

head file # output the first 10 lines of the file
head -n 5 file # output the first 5 lines of the file

32. rename

Syntax : rename [options]

Usage : rename is used to rename multiple files.

Commands Used:

rename 's/old/new/' * # rename all the files in the current directory that contain the old string with the new string

33. tail

Syntax : tail [options] file

Usage : tail is used to output the last part of files.

Commands Used:

tail file # output the last 10 lines of the file
tail -n 5 file # output the last 5 lines of the file

34. tac

Syntax : tac [options] file

Usage : tac is used to concatenate and print files in reverse.

Commands Used:

tac file # concatenate and print the file in reverse

35. comm

Syntax : comm [options] file1 file2

Usage : comm is used to compare two sorted files line by line.

Commands Used:

comm file1 file2 # compare the file1 and file2 line by line

36. cut

Syntax : cut [options] file

Usage : cut is used to remove sections from each line of files.

Commands Used:

cut -d "delimiter" -f "field" file # remove the field from the file using the delimiter

37. sort

Syntax : sort [options] file

Usage : sort is used to sort lines of text files.

Commands Used:

sort file # sort the lines of the file
sort -r file # sort the lines of the file in reverse
sort -n file # sort the lines of the file numerically

38. date

Syntax : date [options]

Usage : date is used to display or set the system date and time.

Commands Used:

date # display the current date and time
date -s "date" # set the date and time

39. cal

Syntax : cal [options]

Usage : cal is used to display a calendar and the date of Easter.

Commands Used:

cal # display the calendar
cal 2019 # display the calendar of the year 2019

40. time

Syntax : time [options] command

Usage : time is used to execute a command and display the time it took to run.

Commands Used:

time command # execute the command and display the time it took to run

41. host

Syntax : host [options] hostname

Usage : host is used to look up the IP address of a host.

Commands Used:

host hostname # look up the IP address of the host with the hostname

42. wget

Syntax : wget [options] url

Usage : wget is used to download files from the web.

Commands Used:

wget url # download the file from the url

43. id

Syntax : id [options]

Usage : id is used to print real and effective user and group IDs.

Commands Used:

id # print the real and effective user and group IDs

44. ps

Syntax : ps [options]

Usage : ps is used to report a snapshot of the current processes.

Commands Used:

ps # report a snapshot of the current processes

45. top

Syntax : top [options]

Usage : top is used to display Linux processes.

Commands Used:

top # display the Linux processes

46. kill

Syntax : kill [options] pid

Usage : kill is used to send a signal to a process.

Commands Used:

kill pid # send a signal to the process with the pid

47. pkill

Syntax : pkill [options] process

Usage : pkill is used to send a signal to a process.

Commands Used:

pkill process # send a signal to the process

48. killall

Syntax : killall [options] process

Usage : killall is used to send a signal to a process.

Commands Used:

killall process # send a signal to the process

49. bg

Syntax : bg [options]

Usage : bg is used to resume suspended jobs in the background.

Commands Used:

bg # resume suspended jobs in the background

50. fg

Syntax : fg [options]

Usage : fg is used to resume suspended jobs in the foreground.

Commands Used:

fg # resume suspended jobs in the foreground

51. tar

Syntax : tar [options] file

Usage : tar is used to create, extract, or list files from a tar archive.

Commands Used:

tar -cvf file.tar file # create a tar archive
tar -xvf file.tar # extract a tar archive
tar -tvf file.tar # list the contents of a tar archive

52. gzip

Syntax : gzip [options] file

Usage : gzip is used to compress or expand files.

Commands Used:

gzip file # compress the file
gzip -d file.gz # expand the file