linux commands

                                                                                LINUX COMMANDS

Ø  Date: To print the system date and time

Syntax:  $ date

Mon Dec 3 10:25:23 EDT 2012

Ø  Who: this command is used to get information about all users who are currently loged onto the system

Syntax: $ who

hari Hy 19 may 19 12:34

Raj Hy 19 may 19 12:45

Ramu Hy 19 may 19 12:56

$ who am i: - Prints information about yourself.

Raj Hy 19 may 19 12:34

Ø  Echo: it displays on the screen whatever is typed after the command.

Syntax: $ echo hello,Linux

O/P:- hello,Linux

Ø  Clear: clear the screen

Syntax: $ clear

Ø  PWD: (Present Working Directories)

It displays present working directory

$ pwd

/root

Ø  Mkdir: for creating new director

Sntax:

$ mkdir dirname

$mkdir user-> it creates directory with name user.

Ø  Rmdir: it is used to remove the directory. Before using this command the directory must be empty.

$rmdir user-> it deletes user directory

Ø  Man: it provides the manual or help for the command

$man rmdir-> it gives the manual for rmdir

Ø  Cd: it is used to change the directory

$ cd user

Ø  Ls: this command lists the files  or  directory ’s

$ls

Ls-l: it gives long listing files

It gives the following data

·         Permissions of a file

·         No.of links

·         Owner

·         Group

·         Size of file

·         Date

·         Time

·         Filename

Ø  Cat : This commands is used to create a file.

Syntax :  $ cat  > filename

Ex: $cat  >hello

Hi

Every body

This is first linux file

Jsdjkd

Adj

Press ctrl + d

Save & terminate the cursor

Again we want see the content of a file we are using cat command

Syntax: $cat filename

$cat hello à display the content of hello file

How to run ‘c’ program in linux

Steps are: 

7)  

 Syntax:-  $ vi first.c

Press ‘I’ key on keyboard

Type the program like

#include<stdio.h>

main()

{

printf(“welcome to linux”);

}

Then press ‘Esc’ key on keyboard

Hold ‘shift’ key and press ‘:’ key on keyboard

Enter wq and press enter key

Now u r program is save and exit

Now compile the program using

$cc (or) gcc first.c

If any errors then back to u r program using vi first.c

And modify program and follow above same steps.

After compile run the program using this command

./a.out,

get output of the program

welcome to linux

Ø  rm : this command is used to delete the file.

$rm filename

$rm hello

Ø  cp(copy): it copies the contents of one file to another file

Syntax:$cp filename1 filename2

Ø  mv : move the filename1 to filename2(rename)

Syntax:$mv filename1 filename2

Ø  sort: this command is used to sorts and merge files

Before executing the sort command, first we need to create two files using cat command

$cat  > cmr1

Hfj hfjk hjksf

Sfj jf  fjs sjk

$cat  >cmr2

Njk dfj kdjf kfj

Dnfjk hjkf f

Dfn

Syntax: $sort file1 file2  >file3

The contents of file1 and file2 are merged, sorted and stored into file3.

          Example : $cat cmr1 cmr2  > cmr3