SHELL PROGRAMING

• Union command are executed ,when they are typed in shell prompt.
• A shell program is nothing but a series of such command.      
• Instead of specifying,job at a time we give the shell to do test a program that carries out entire procedure such program are called shell scripts.
• use shell is an interface between user and operator system.
• The shell programming evaporates most of the feature that most modern programming longs for assemble, it has local and global variables control instruction functions etc..
• To execute a shell program,we don't read a separator  compile.the shell itself interprets the commands & executes that...
• shell programming is so powerful that several tastes like system shutdown, checking how
• much disc space is available etc.. are carried out by shell script.
•  variable name.

operate name

logical                                        

-a    -gt

-0    -lt

-1    -ge

• Read used to accept input&output from keyword read name. 

• echo use to display the massage & value at variable.
• $echo hello 
• $echo name
• $ indicate
• value in  the variable name 
• assigning value variable name=value
• Arg1,Arg2..........Arg n are command lie arguments & are received in the program as $1,$2.....$n.