What is Shell Script ? Why want to create Shell Script?

• A shell script is a text file with Unix commands in it.
• Shell scripts usually begin with a #! and a shell name (complete path-name of shell).
• Path-name of shell be found using the which command.
• The shell name is the shell that will execute this script.
• If no shell is specified in the script file, the default is chosen to be the currently executing shell.

 E.g:
#!/bin/bash
 echo “Hello World”;
 exit 0;

Here
       #!/bin/bash    -  shell name , the program will execute this environment 


Why want to write shell script?

To avoid repetition:

• If you do a sequence of steps with standard Unix commands over and over, why not do it all with just one command?
• Or in other words, store all these commands in a file and execute them one by one. 

To automate difficult tasks:

 

Many commands have subtle and difficult options that you don’t want to figure out or remember every time .

To run the script:
$ chmod u+x myscript #set executable permission
$ ./myscript #Each line of the script is processed in order
       

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Why write shell scripts

Why write shell scripts ?