This blogpost gives a list of 30 Most Frequently Used Linux/Unix Commands With Examples. I tried to list out the most frequent commands, which will be useful for any Linux user in day to day life. I have also given examples with each command so that it will be easy for you to understand.
1. ls Command Examples :
This is the most frequently used linux command and it list the the current directory.
ls without any option list the current working directory
# ls ODBCDataSources gai.conf mail rc4.d X11 gconf mail.rc rc5.d adduser.conf gnome mailcap rc6.d
By default ls without option won’t show the hidden files, to view the hidden files type
# ls -a . fstab.d magic.mime rc4.d .. ftpusers mail rc5.d .pwd.lock gai.conf mail.rc rc6.d ODBCDataSources gconf mailcap rcS.d
to list files in Human Readable Format use the option -lh
# ls -lh drwxr-xr-x 2 root root 20K Jul 2 15:56 bin drwxr-xr-x 2 root root 4.0K Oct 23 2013 games drwxr-xr-x 35 root root 4.0K Jul 2 15:55 include drwxr-xr-x 51 root root 4.0K Jun 28 13:26 lib drwxr-xr-x 10 root root 4.0K Oct 23 2013 local
to list files ordered by Last Modified Time use option -ltr
# ls -ltr drwxr-xr-x 2 root root 4096 Oct 23 2013 src drwxr-xr-x 10 root root 4096 Oct 23 2013 local drwxr-xr-x 2 root root 4096 Oct 23 2013 games drwxr-xr-x 51 root root 4096 Jun 28 13:26 lib
2. cd Command Examples
to change the directory in linux we use cd command
[email protected]:/usr# cd bin [email protected]:/usr/bin#
to goto one level up use cd .. command
[email protected]:/usr/bin# cd .. [email protected]:/usr#
3. man Command Examples
sometimes you remember the command but forgot the options available with it, man command helps you here. It will show the manual of the command and list out all the options available with that command. Lets check ls command manual
[email protected]:/# man ls SYNOPSIS ls [OPTION]... [FILE]... DESCRIPTION List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor --sort is specified. Mandatory arguments to long options are mandatory for short options too. -a, --all do not ignore entries starting with . -A, --almost-all do not list implied . and .. --author with -l, print the author of each file -b, --escape
it will show you all the options and their uses, to exit from man press q.
4. cp Command Examples
The cp command is used to copy one file to other
# cp file1 file2
using cp with -p option will preserve the mode, ownership and time. using cp with -i option will prompt for overwriting the file.
5. mv Command Example
The mv command is used for move operation from one location to other.
to move the file from one location to other use command
# mv /usr/file1 /usr/bin/file1
it also acts as a rename command and to do that type
# mv file1 file2
above command will rename the file1 to file2
6. mkdir Command Example
In Linux/Unix we use mkdir command to create new directory, but to do that you must have write permission.
# ls bin file1 games include lib local sbin share src # mkdir temp # ls bin file1 games include lib local sbin share src temp #
if you need to create nested directory then you can use mkdir -p command
# mkdir -p temp1/temp2/temp3 # ls bin file1 games include lib local sbin share src temp temp1 # cd temp1 temp1# ls temp2
7. chmod Command Example
chmod command is used to set the permission on files or directory or alter previously set permission. Permission can be set using symbolic or octal codes.
u user + to add a permission r read g group - to remove a permission w write o other = to assign a permission explicitly x execute
to add read, write and execute permission for file we can do this by
chmod u=rwx tempfile
to add read and write permission to any directory we can do this by
chmod u+rw dir1
8. date Command Example
date returns the current date and time of the system
# date Tue Jul 29 13:42:51 EDT 2014
We can also format the output of date command like this
# date '+The date is %d/%m/%y, and the time is %H:%M:%S.' The date is 29/07/14, and the time is 13:43:43.
9. file Command Example
Some times you need to know the type of any file or what type of data it contains then you can use file command.
# file file1 file1: ASCII text
10. tar Command Example
To compress a file you can use tar command.
# tar cf demo.tar temp # ls bin demo.tar file1 games include lib local sbin share src temp
above command will create a archive demo.tar with contents of temp directory. To see the content of tar archive use this option
# tar tvf demo.tar drwxr-xr-x root/root 0 2014-07-30 13:03 temp/ -rw-r--r-- root/root 14 2014-07-29 14:04 temp/file1
to extract the content of archived file use xf option. Here x means extract and f means file. It will copy the content of archive in current directory.
# tar xf demo.tar
11. grep Command Example
Some time you need to search with a pattern because you forgot the file name but partially you remember, in that case you can use grep command.
# grep is file1 this is file1
In above example output will come with is highlighted in red. With grep you can search in multiple file for the same pattern
# grep is file1 file2 file3 file4
Also if you need to search for word codingbyte in all the available files which name is starting with a and are present in current directory type this.
# grep codingbyte a*
12. ssh Command Example
ssh command is used to login to remote host securely. It provides encrypted communication between client and host.
ssh -l jsmith host.abc.com
13. rmdir Command Example
To remove a directory you can use rmdir command. The directory you are removing must be empty.
# rmdir temp
If you need to deleted a directory which is not empty you can use option -r with rmdir
# rmdir -r demo
14. rm Command Example
rm Command is used to remove a file or directory. To remove a file you must have write permission on the directory where file reside.
# rm file1
Before deleting if you want a confirmation then you can use -i option
# rm -i file1 rm: remove regular file 'file1'? y
to remove a directory and all the contents of it, you can use -r option
rm -r temp
Above command will first recursively delete the all the files from directory and sub directory and then delete the temp directory itself.
15.pwd Command Example
pwd command will show the current working directory of logged in user
# pwd /usr/temp
16. ps Command Example
ps command is used to check the current running processes on the system. It will list out the process id and other detail of the process.
# ps PID TTY TIME CMD 17488 pts/0 00:00:00 bash 19364 pts/0 00:00:00 ps
To see the full detail of processes use the option fu with ps
# ps fu USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 17488 0.0 0.2 18120 2068 pts/0 Ss 12:48 0:00 -bash root 19407 0.0 0.1 15520 1152 pts/0 R+ 14:17 0:00 \_ ps fu
17. passwd Command Example
If you need to change the password then you can use passwd command.
# passwd Enter new UNIX password:
18. more Command Example
Suppose you want to open a big file and read it page by page, this you cannot do with cat command. more command allow you to read a big file one page at a time. To quit before reaching end of file press q
# more file1
19. kill Command Example
To kill a running process you can use kill command, this command requires process id and that you can get from ps command.
# kill 19633
20. lpr Command Example
To send the content of a file to print use lpr command.
# lpr -Pprinter1 file1
Here printer1 is the name of printer and file1 is the file you are going to print.
21. gzip Command Example
gzip command is used to create .gzip compressed file.
# gzip demo.txt
To uncompress the above file use below command
# gzip -d demo.txt.gz
22. unzip Command Example
To uncompress the .zip file use unzip command
$ unzip demo.zip
It is also possible to see the content of zip file without uncompressing the file
unzip -l demo.zip
23. shutdown Command Example
To turn off your system of schedule the turnoff you can use shutdown command
# shutdown -h now
Above command will turn of the system instantly. To schedule the turnoff after 20 minutes use below command
# shutdown -h +20
to reboot the system you can use below command
# shutdown -r now
24. free Command Example
To check the usage of memory you can use free command. It will show the free memory, used memory and swap memory .
# free total used free shared buffers cached Mem: 786432 371760 414672 0 0 199080 -/+ buffers/cache: 172680 613752 Swap: 0 0 0
You can format the memory display using -b, -k, -m and -g .
# free -m total used free shared buffers cached Mem: 768 348 419 0 0 194 -/+ buffers/cache: 154 613 Swap: 0 0 0
25. top Command Example
To see the top processes from the system use top command. It will show the list sorted by cpu usage
top - 15:03:48 up 31 days, 3:10, 1 user, load average: 0.18, 0.19, 0.10 Tasks: 27 total, 1 running, 26 sleeping, 0 stopped, 0 zombie %Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem: 786432 total, 397332 used, 389100 free, 0 buffers KiB Swap: 0 total, 0 used, 0 free, 199900 cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1 root 20 0 26488 1064 288 S 0.0 0.1 0:05.47 init 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd/3722 3 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khelper/3722 50 root 20 0 15224 8 4 S 0.0 0.0 0:00.00 upstart-file-br
26. df Command Example
df command is used to see the disk usage of filesystem.
# df Filesystem 1K-blocks Used Available Use% Mounted on /dev/simfs 52428800 2320664 50108136 5% / none 393216 4 393212 1% /dev none 4 0 4 0% /sys/fs/cgroup none 78644 1056 77588 2% /run none 5120 0 5120 0% /run/lock
We can format the output using -h option, it will show the output in human readable format.
# df -h Filesystem Size Used Avail Use% Mounted on /dev/simfs 50G 2.3G 48G 5% / none 384M 4.0K 384M 1% /dev none 4.0K 0 4.0K 0% /sys/fs/cgroup none 77M 1.1M 76M 2% /run none 5.0M 0 5.0M 0% /run/lock
27. whereis Command Example
To search the location of a specific linux command or a specific name you can use whereis command.
# whereis cat cat: /bin/cat /usr/share/man/man1/cat.1.gz
# whereis apache2 apache2: /usr/sbin/apache2 /etc/apache2 /usr/lib/apache2 /usr/share/apache2 /usr/share/man/man8/apache2.8.gz
28. whatis Command Example
As name suggest whatis command will show one line description of any command .
# whatis cat cat (1) - concatenate files and print on the standard output # whatis ls ls (1) - list directory contents
29. tail Command Example
Suppose you want to see the last few lines of the file then you can use tail command. By default it will show 10 lines.
# tail file1
you can also define how many lines you want to see by using -n option. In below command it will show the N lines from the tail of the file1.
tail -n N file1
30. wget Command Example
wget is used to download the software and other files from the internet. In my last post How To Install WordPress on Ubuntu VPS i have used this command to download the wordpress setup file from wordpress server.
I have tried my best to list out the 30 Most Frequently Used Linux Commands and given their example. Please give your suggestion in the comment and also share the post.