COMMAND LINE INTERFACE IN LINUX
LINUXCOMMAND LINE INTERFACE15-09-2013 GUNAANBAN.G
[email protected] is Command Line Interface in Linux?
Actually its a terminal. Which is a command prompt in Windows.
Two kind of terminals are there. They are,
Terminal Emulator GUI (Alt+Ctrl+T)
Text Based terminal (Alt+Ctrl+F1 / F2 / F3 / F4 / F5 / F6)
/ - represents orText based terminal can be used by six or less
no. of users at a time.
While entering into each terminal it will ask for user name and
password to identify particular user.
Same user can work on different terminals at a time.
To exit from terminal to Graphical User Interface the below
shortcut key is used Alt+Ctrl+F7 COMMANDSStarting with the basic
Command man
man represents Manual.
This command used to give the instructions about the
command.
For example, man sudo command gives the instructions about sudo
command.
Command dir dir stands for directory.It is used to display the
files and folders within that directory. It displays file with its
extension.
Command mkdir mkdir stands for make directory. This command is
used to create a directory. The syntax is,mkdir foldername
Command rmdirrmdir stands for remove directory. This is used to
remove the directory. Make sure that the directory should be empty.
The syntax is,rmdir directory_name
Command - ls
It displays a list of files in the current directory in
alphabetical order. It also differentiate the file name using
colors with respect to their permissions.
This command can be used with some options like ls a and ls l
.
Command ls a : ( It displays all directory including hidden
files)
Command ls l :It displays all directory and files along with
their user access permissions.
Command clear clear command is used to clean the screen of the
terminal window. Before clearing,
After clearing the screen,
Command - cd It is used to change the directory. cd stands for
change directory. Example given below as cd gisak.
The command cd . is used to stay on the same directory.
The command cd .. is used to go back to the previous
directory.
The command cd is also used to redirect to the home
directory.
Command pwd pwd stands for print working directory. It is used
to display the path of current working directory. The syntax is
,pwd
Command datedate command is used to display the current system
date and time.
Command cat cat command is used to create a file. The syntax is
cat > filename text here Ctrl + dExample is,
Command sh sh command is used to run the program in the file.
The syntax is ,sh file_name
Command mv mv command is used to rename the file and also move a
file from one directory to another. The syntax for renaming a file
,mv old_name new_name
mv command used for moving files. The syntax is ,mv path1/file
path2/
cat command is used to view the content of the file. The syntax
is ,cat filename
cat command also used to concatenate two files and redirect the
output to another file. The syntax is ,cat file1 file2 >
outputfile
Command cmp cmp command is used to display the difference
between the contents of the two files. The syntax is , cmp file1
file2
In the above example, the output shows that, the variation
starts from the sixth character(byte 6) in the first line(line 1)
.
Command diff diff command is used to give the changes in the
files while copying one directory to another. It have three
different ways in describing difference between the files. They
are,Changed to , Addition to , Deleted to.
The syntax is,diff original_file copied_fileIn the above output,
3c1 says that 3 line changed to a single line while copying the
file. 1c1 says that 1 line is changed upto 3 line.
In the above output, 1a2 says that 1st line is equal and
addition to 2 and 3 lines.
In the above output, 3d1 says that 2nd and 3rd line are deleted
while copying the file.
Command cp cp stands for copy. This command is used to copy the
content of the one file to another file. The syntax is ,cp
source_file destination_file
Command wc wc stands for word count. It is used to count the
content of the file. The syntax is ,wc filename
wc l is used to display no. of line in the file. wc c is used to
display no. of characters in the file. wc w is used to display no.
of words in the file.
Command find find command used to search a file with some
constraints. The syntax is,find
Command more more command is used display the large content file
in the terminal window by percentage basis. The syntax is,more
filename
The percentage based examples for more command is given
below.
Just click enter to see next line Finally it automatically
return to normal window. It can be stopped by clicking Ctrl+z .
Command sort sort command is used to display the content of the
file in ascending order. The syntax is,sort filename
sort b command ignores the blank space and displays the content
of the file in ascending order. The syntax is ,sort b filename
Command greb greb command is used to display the same content in
2 different files. The syntax is, greb file1 file2
Command paste paste command is used to combine two various file
contents. The syntax is,paste file1 file2
Command vi vi command used to open a file using Command Line
Editor.
We can edit the file by clicking the insert button on the
keyboard. After editing the file, click the insert button
again.After changing text in the file, save the file and exit.
enter :wq .
To discard the changes and exit the file, enter :q .
Make sure that the file has the permission to write.. Otherwise
below output will be shown.
Command rm rm command is used to delete a file. The syntax is,rm
filename
Command whoami whoami command is used to show the current login
user name. The syntax is,whoami
Command su su stands for super user. It is used for login from
one user to another. More likely log off method.
su l command is used for switch user login to root login. Then
it ask for root password.
To come back to normal use the command logout .
Command who who command is used to display the login users with
their terminal details. The syntax is,who
Command chmod chmod stands for change mode. This command is used
to change the file permissions. This command offers symbolic and
numerical way for changing the modes. The syntax is ,chmod
filename
File before changing the permissions.
Restricting the reading and writting permission of the file in
numerical way.
Opening the file, after restricting the permissions.
Providing permissions to the file in numerical way.
Removing permissions of the file in symbolic way.
Providing permissions to the file in symbolic way.
In changing the group, it has 3 types. They are,User , Group ,
Other.In Operations ,it also has 3 types . They are, + , - , =In
changing the modes, it also has 3 types. They are,read(4) ,
write(2) , and execute(1)
Command | | is a pipeline command. It is used to join 2
commands.
It displays 4 users are working on different terminals at the
same time.
Command wall wall command is used to display messages to all the
users on different terminals at a same time. The syntax is
,wall
Sender side
Receiver side.
Command adduser adduser command is used to add a new user to the
system. The syntax is,adduser username
Command passwd passwd command used to change the password of the
user. The syntax is,passwd username
Command userdel userdel command is used to delete the user id.
The Syntax is ,userdel username
Command sudo passwd rootsudo passwd root command is used to
change the passwd of the root from the user by using super user
facility. In this user must have the administrator permissions.
Guest users are not allowed to change this.
Command shutdownshutdown command is used to halt or stop all the
system processes. The syntax is,shutdown shutdown r now command is
used to restart the computer.
shutdown h now command is used to shutdown or suspend the
computer.
The Admin user root can only use this commands.
Command initinit command is also used in halting the system
performance.The syntax is,init
init 0 Command is used to shutdown or suspend the computer.
This command is also only used by the root user.
Thank you
