DevOps(Day-4)

Shell scripting in LINUX

1. What is Shell Scripting?

   It is a set of commands written in an executable file to automate any task. The commands are converted then to machine-readable form to execute.

   Syntax:-

   #!/bin/bash

   <commands>

   The file to be created must be with extension ".sh" and provided with necessary execute permissions to the user running the script.

2. What is `#!/bin/bash'? can we write `#!/bin/sh` as well?

   #! is called Shebang. It contains the path (/bin/bash) which uses the shell for executing the code written in the script file.

   BASH - Bourne again shell

   /bin/bash can execute the majority of scripts thus it is used widely.

   /bin/sh is an executable representing the system shell and is usually implemented as a symbolic link pointing to the executable for whichever shell is the system shell. The system shell is the default shell that the script should use.

   Basically, it points to /bin/bash but nowadays it became /bin/dash which is faster.

3. Write a Shell Script which prints `I will complete #90DaysOofDevOps challenge`

   vim first_script.sh

   ---

   #!/bin/bash

   echo "I will complete #90DaysOofDevOps challenge"

   ---

   Chmod 777 first_script.sh

   ./first_script.sh

   

   

4. Write a Shell Script to take user input, input from arguments and print the variables.

   #!/bin/bash

   echo "Hello I am $1"

   

   

5. Write an Example of If else in Shell Scripting by comparing 2 numbers

   #!/bin/bash

   a=10

   b=20

   if [[ $a -gt $b ]]

   echo "a is greater than b"

   else

   echo"b is greater than a"