LINUX BASICS

Linux is a 100% free operating system which is specially designed for multitasking, multi-user networks that is similar to Unix. -Linux was created by ×Linus Torvalds in 1991.

Linux Architecture
















Linux file system
A file system is the way how system contains and stores all your files like your documents, games, programs, music, videos etc.In Linux world, the same theory holds true you have directories and  folders in which you arrange your files.

Basic Linux commands

COMMAND	SYNTAX	DESCRIPTION	EXAMPLE
pwd	pwd	Identifying the current directory path	[student@localhost student]$ pwd /home/student
mkdir	mkdir directory name	Creating a directory	mkdir directoryname
cd	cd directory name	Changing the current directory	cd  user/bin
rmdir	rmdir directory name	Removing a directory	rmdir filename
ls	ls options are: -l,-a,-r	To display the names of files and subdirectories that are stored in a directory	ls /home/student
ps	ps	Display the shell	ps
who	who	Display the information about users who are logged in	who
clear	clear	To clear the screen	clear
cat	Cat>filename	Create file	Cat>file1 content cntrl+z
cat	cat  filename	To display the contents of a specified file.	cat file1
	Cat File1 file2	To display the contents of more than one file	cat file1 file2
cp	cp [options] <source files> <destination files/directory>	To copy the contents of the source file into a target file.	cp file1 file2
rm	rm [option] file/s option are:	To delete files/directories.	rm file1
mv	mv [option] source destination	To move file or directory from one location to another	mv temp emp
Wildcard character             *	*	Matches none or one character or string of characters.	cat c*
?	?	Displays all files that contains any characters before a period followed by exactly one character after a period.	ls *.?
head	head [option] [filename]	To display the specified number of lines from the beginning of a file.	head-3 file1
tail	tail [option] [filename]	To display the specified number of lines from the end  of a file.	tail -3 file1
find	find [path] [expression] Options:	To locate in a specific directory and its subdirectories	find /home/student/
	-name	To specifies the name of the files that you need to locate	find /home/student/                            -name “jan”
	-type	To locate a specific type of file.	find /home/student/        -type f(search all the ordinary files)
	-exec	To specify the operations that need to be to be performs on this that have been located by the find command	find -name temp -type  f –exec rem {} \;
	-ok	Used with find command which prompt the user for a conformation before executing the command for each file.	find –name temp –type f –ok rm {} \;
touch	touch filename	This command is used to creating empty file.	touch file3
Filters: grep	grep regular_epr [filename] Options: -a,-n,-c	Searches a file for a specified pattern of characters and displays all the lines that contain the pattern.	grep hai text
pipes	|	It helps to combine two or more commands	ls  | more
vi editor	Visual editor	Write a program , compile it and run it	At shell prompt $vi programname.c Press i for Insert Type the program code Press  esc   : (colon)  wq (write & quit) Compile program At prompt  $ gcc programname.c Execute program  $./a.out program name