Some Linux Commands !!!

COMMAND	DESCRIPTION	SYNTAX
who	show who is logged on	who
su	change user ID	su <loginname>
passwd	to change your password	passwd
man	displays details of a command	man <command_name>
ls	list directory contents	ls
mkdir	make directories	mkdir <foldrname>
cd	changes directories	cd
cp	copy files and directories	cp a.txt copy.txt
mv	move files	cp a.txt <directory>
rm	remove files or directories	rm file1.txt
find	search for files in a directory	find file1.txt
pwd	print name of current working directory	pwd
history	prints recently used commands	history
mount	mount a file system or drive	mount /media/target
umount	unmount file systems or drive	unmount /media/target
poweroff	shut down the system	poweroff
reboot	restart the system	reboot
vim	A programmer’s text editor	vi hello.c
gedit	A text Editor	gedit hello.c
cal <month> <year>	display calendar	cal april 2012
date	displays the current date	date
echo	Print message on the terminal	echo "Welcome to the workshop"
printf	Print the formatted message on the terminal	printf "the amount is %d\n" 100
bc	A text based calculator	bc
xcalc	A graphical based calculator	xcalc
gcc	To compile C program file	gcc file1.c
g++	To compile C++ program file	g++ file1.c
ctrl+d	Quit command process

FIRST PROGRAM –“HELLO”

In this blog we are discussing about the first LINUX program – printing ‘HELLO’ on screen – using GCC. Programming in Linux is same as programming in Windows TC. For this, start your Linux, open user’s “Home Folder”. Home folder is accessed from ‘Places’ menu from Left corner of Upper Taskbar or from left sidebar on Desktop. Home folder name can be your login name. Then right click on empty space, you will get property menus- Create Folder, Create Documents, Arrange items, etc… Select ‘Create Documents à Empty file’ menu. It will create an empty file with name ‘new file’; rename it with ‘hello.c’ (small letters compulsory). Then you can write your C code in it. Let C code is –

#include<stdio.h>

int main()

{

            printf(“\n\n HELLO \n\n”);

            return 0;

}

Now,

 In TC (Windows), we are including “conio.h” header file in C code. Also we are using clrscr(), getch() functions. But in Linux, we are not using it. It has a reason. Because “conio.h” header file is not an ANSCII approved header file. Linux GCC has only ANSCII approved header files and include only them.

If you try to include them in C code, then Terminal (GCC) will give error that ‘conio.h file can’t be included’.

Now, close the “hello.c” file. Open Linux Terminal, it is in “Application” menu in left corner of upper taskbar or from left sidebar. Navigate terminal to “hello.c” file directory (if necessary, using cd command). Then type one of the following commands.

1)    gcc hello.c

If C-code is syntactically correct, then on Terminal there will not be any error message and you will get “a.out” executable file in same directory otherwise prints errors of C-code with line no. on Terminal.

2)    gcc hello.c –o hello.ext

It is same is first command but it creates “hello.ext” executable file except “a.out” in same directory. You can give any filename and extension in command.

3)    gcc hello.c –Wall –Werror –o hello.ext

It is same is first command but if C-code contain any warnings then these will be printed on Terminal as errors and if C-code is syntactically correct then it creates “hello.ext” executable file in same directory.

Now, you got “a.out” or “hello.ext” executable file on directory. For running it on Terminal, you have to give a command like-

./a.out                 OR

./hello.ext

a.out or hello.ext file gets executed and you will get result on Terminal screen.

PICTORIAL PROCEDURE IS AS FOLLOWS =