Shell Scripting in Linux
What is Shell?
Shell UNIX term for an interface between a user and an service. Shell provides users with an interface and accepts human-readable commands into the system and executes those commands run automatically the program’s output shell script.
Types of Shell
There are two main shells in Linux:
1. The Bourne Shell: The prompt for this shell is $ and its derivatives are listed below:
- POSIX shell sh
- Korn Shell also knew as sh
- Bourne Again SHell also knew as bash (most popular)
2. The C shell: The prompt for this shell , and its subcategories are:
- C shell csh
- Tops C shell tcsh
How to Write Shell Script in Linux/Unix
Shell Scripts are written using text editors. On your Linux system, open a text , open file typing a shell script or shell programming, then give the shell permission to execute your shell script and put your script in from where the shell can find it.
Choosing A Text Editor
Shell scripts are text-based files. your scripting journey, choose a text editor that works best for you. Linux distributions pre-installed text editors, but commonly used ones are listed below:
- vi – Usually installed by default. Preferred by administrators because editor small in size .
- emacs – contains of features but beginner-friendly
- pico – a simplified version of emacs (without the features)
- nano – a pico but comes with features
- Create a file vi editor(or editor). Name script file with extension .sh
- Start the script with #! /bin/sh
- Write some code.
- Save the script file filename.sh
- For executing the script type bash filename.sh
- “#!” is an operator called shebang which directs the script to the interpreter location. So, if we use”#! /bin/sh” the script gets directed to the bourne-shell.