Linux common commands

Linux common Commands

To view help about command

Command: man command_name

Creating file with touch 

Command: touch  "file name"

Example : touch "application properties"

Creating file with Contents

Command: cat > file_name press enter button
        
                          Type file contents
         
                          Close it with ctrl+Z

Creating Directory command

Command: mkdir directory_name

Creating more than one directory

Command: mkdir directory1 directory2

View current user info

Command: who am i

View Present working directory

Command: pwd

View System time

Command:  date

View current month calender

Command: cal

Shifting LINUX terminal with commands

It has seven terminals( 6 - CUI terminals, 1 - GUI terminal)
Commands:      chvt 1            Short cut: ctrl + alt + F1
                        chvt 2                           ctrl + alt + F2
                        chvt 3                           ctrl + alt + F3
                        chvt 4                           ctrl + alt + F4
                        chvt 5                           ctrl + alt + F5
                        chvt 6                           ctrl + alt + F6
GUI Terminal:  chvt 7                            ctrl + alt + F7

 Shut down

Command : init 0

Creating Hidden Files

Command: touch . filename

Creating Hidden Directory

Command: mkdir . directory_name

Creating hierarchy of directories

Command: mkdir -P directory1 | directory2 | directory3

View file contents

Command: cat filename

Viewing Present working directory contents

Shows the files in the present working directory

Command: ls

Long listing of the files and directories in the present working directory

Command : ls -l

View all files including hidden files

Command: ls -a

Long listing of the files including hidden files

Command: ls -al

Recursively displays directories and sub directories

Command: ls -R

To filter display files list

Command: ls  ?some_text

Command: ls  *some_text

Ranging specifying

Command: ls [a-d]some_text

Command: ls [^a-d]some_text

Changing directory 

Moves one directory up

Command: cd .. 

Three steps back (Some steps back)

Command: cd ../../..

Three steps to front (Some steps to front)

Command: cd directory_name1/directory_name2/directory_name3

Going back to home directroy

Command: cd ~

Going back to previously working directory

Command: cd -

Deleting empty directory

Command: rmdir directory_name

Deleting non-empty directory

Command: rm -r directory_name

Deleting file

Command: rm filename

Moving file(Cut and paste)

Command: mv source     destination

Renaming file

Command: mv old_file_name new_file_name

Copy file

Command: cp source_file_path destination_path

Searching text in file

It is used to search a particular text in a file or in a directory

Command: grep some_text file_name

To search text in present working directory

Command: grep some_text  . 

Command: grep some_text directory_name

Creating user

Command: useradd user_name

Command: passwd user_name

Deleting user

The following command deleted user but does not delete directory from home directory

Command: userdel user_name

To delete user along with the directory at home

Command: userdel -r user_name

Process Killing

Command: kill i_node_number

To view current list of users logged in along with personal information

Command: finger

Changing Permissions after creating file

The following command gives permissions read, write and execute to owner, group and others

Command: chmod  777

 Example to give write permissions to user

Command: chmod u+w

Example to remove write permissions to user

Command: chmod u-w

Example to give write permissions to  group

Command: chmod g+w

Example to remove write permissions to  group

Command: chmod g-w

 Example to give write permissions to others

Command: chmod o+w

Example to remove write permissions to others

Command: chmod o-w

To view all previously executed commands

Command:  histroy

To display first n number of lines of the file

Command: head -n file_name


Example: head -2 file_name

It displays first two lines of the file

 To display last n number of lines of the file

Command: tail -n file_name

Example: tail -2 file_name

It displays last two lines of the file

Displaying multiple files simultaneously 

Command: pate file_name_1 file_name_2 file_name_3

Translate  

Command: tr 'a-z' 'A-Z' file_name

Sorting file contents

Command: sort file_name

Going to other shell

Simply type shell name : sh
                                     ksh

df –h command

It displays - device name, total blocks, total disk space, used disk space, available disk space and mount points on a file system.

-h Human Readable format

su - substitute user or switch user

su – another_user

ps -command

This command is used to view processes running on the system.

Examle : ps –ef | grep apache

chown

chown chnages owner or group ownership.

Examples:

1       1) home/abc_dir$ chown new_owner_user  helloworld.txt

the above command changes holloworld.file owner to “new_owner_user”.

2    

          2)      home/abc_dir$ chown new_owner_user  *

The above command changes contes of abc_dir and sub folders owner to “new_owner_user”.

3     

          3)      home/abc_dir$ chown new_owner_user:web_group  helloworld.txt

the above command changes holloworld.file owner to “new_owner_user” and owner group to “web_group”.

4      

          4)      home/abc_dir$ chown new_owner_user: web_group  *

The above command changes contes of abc_dir and sub folders owner to “new_owner_user” and owner group to “web_group”.

Locate Linux command:

This command is used to find the locations of files and directories in Linux.

Syntax:locate options names

Example 1: locate abc.png

The following example displays only screenful of output at a time.

Example2: locate "*.html" | less

nslookup(name server lookup) command:

Syntax: nslookup domain_name

Example: $ nslookup csesss-lx00034

It transforms domain name to IP address.

more command:

It shows first page contents.

Syntax: more file_name 

press space bar to view next page contents.

press enter to view next line contents.

Vi Editor commands: 

It opens existing file, if file exists other wise it creates.

vi file_name 

Following commands opens file in read mode

vi –R file_name
view file_name

Closes file after writing changes to file.

:wq!

Closes file without writing changes to file.

:q!

Moves cursor to starting of the current line if file is not in insert mode.

0

Moves cursor to end of the current line if file is not in insert mode.


$

x  - removes one character in command mode.

Running shell script:

It runs specified shell script file.

Syntax 1:  ./file_name.sh

Syntax 2: sh file_name.sh