Friday, 15 May 2015

Linux Basic Commands

To Print Working Directory
Print the name of the current working directory

[root@sanlinux~]# pwd

List of Files and Directories
To see the list of files and directories

[root@sanlinux~]# ls <options> <arguments>

Options

-l – Long list including attributes
-a – All files and directories including hidden
-d – For a particular file or directory
-R – Recursive to see the tree structure
Creation of files

Files can be created by using any of the three methods given below:

    Cat command
    Touch command
    Vi editor

Cat (Concatenation) Command
Creating and displayed text files

[root@sanlinux~]# cat <option> <arguments><filesname>

To create a file

[root@sanlinux~]# cat > <filename>

To view the contents of a file

[root@sanlinux~]# cat <files=name>

To append or add to an existing file

[root@sanlinux~]# cat >> <filename>

To combines the data of two or more files into a third file

[root@sanlinux~]# cat <first file> <second file> >> <third file>

Touch Command
To create a zero byte file

[root@sanlinux~]# touch <filename>

To create multiple zero byte files

[root@sanlinux~]# touch <first file> <second file> <third file>

To change the time stamp of a file or directory

[root@sanlinux~]# touch <directory or filename>

Vi Editor
To create file

[root@sanlinux~]# vi <filename>

Creating Directories
To create a directory

[root@sanlinux~]# mkdir <directory name>

To create multiple directories

[root@sanlinux~]# mkdir <first dir> <second dir> <third dir>

To create nested directories

[root@sanlinux~]# mkdir –p <first dir>/<second dir>/<third dir>

Navigation of Directories
To change the directory

[root@sanlinux~]# cd <path of the directory>

To change directory one level back

[root@sanlinux~]# cd ..

To change directory two levels back

[root@sanlinux~]# cd ../..

To change to the last working directory

[root@sanlinux~]# cd –

To change to the users home directory

[root@sanlinux~]# cd

Help or Manual Page
To view the manual page of a command

[root@sanlinux~]# man <command>

Copying
To copy a file or directory

[root@sanlinux~]# cp <options> <source file> <destination>

Options

-r – Recursive (to copy the directory along with its contents)
-v – Verbose
-p – Copy with permissions
Moving and Renaming
To move a file or directory to a different location

[root@sanlinux~]# mv <source file or directory> <destination>

Rename a file or directory

[root@sanlinux~]# mv <old name> <new name>

Deleting
To remove or delete an empty directory

[root@sanlinux~]# rmdir <directory name>

To remove or delete a file or directory

[root@sanlinux~]# rm <option> <file or directory name>

Options

-r – Recursive (directory along with contents)
-f – forcefully
Some other commands
To see the date

[root@sanlinux~]# date

To see the calendar

[root@sanlinux~]# cal

File Viewing Commands
To view the contents o f a file screen-wise

[root@sanlinux~]# less <file name>

To view the top lines of a file

[root@sanlinux~]# head <filename>

[root@sanlinux~]# head -5 <filename>

To view the bottom line of a file

[root@sanlinux~]# tail <filename>

[root@sanlinux~]# tail -3 <filename>

VI editor modes

VI editor has three modes of operations

    Command Mode
    Insert mode
    Ex Mode (Extended Command Mode)

Insert Mode

I – Insert the text at the current cursor position.
l – Insert the text in beginning of a line
a – Adds the text after the current cursor position
A – Adds the text at the end of a line
o – Insert the text one line below current cursor position
O – Insert the text one line above current cursor position
Ex mode

:q – Quit without saving
:q! – Quit forcefully without saving
:w – Write (save)
:wq – Save and quit
:wq! – Save and quit forcefully
:se nu – sets line numbers
:se nonu– Remove line numbers
:84 – The cursor goes to line 84
Command Mode

dd – Deletes a line
ndd – Deletes ‘n’ lines
yy – Copies a line
nyy – Copies ‘n’ lines
p – Put (pastes the deleted or copied text)
u – Undo(you can undo 1000 times)
G – Moves the cursor to the last line of the file

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