Shell Scripting

A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be command languages. Typical operations performed by shell scripts include file manipulation, program execution, and printing text. Shell scripting is primarily used to automate repetitive system tasks, such as backing up files, monitoring system resources, and managing user accounts. By turning a series of commands into a script, system administrators can save time, increase accuracy, and simplify complex tasks.

Usually, shells are interactive, which means they accept commands as input from users and execute them. However, sometimes we want to execute a bunch of commands routinely, so we have to type in all commands each time in the terminal. As a shell can also take commands as input from file, we can write these commands in a file and can execute them in shell to avoid this repetitive work. These files are called Shell Scripts or Shell Programs. Shell scripts are similar to the batch file in MS-DOS. Each shell script is saved with .sh file extension e.g., myscript.sh.

A shell script has syntax just like any other programming language. If you have any prior experience with any programming language like Python, C/C++ etc. It would be very easy to get started with it.

A shell script comprises the following elements –

• Shell Keywords – if, else, break etc.
• Shell commands – cd, ls, echo, pwd, touch etc.
• Functions.
• Control flow – if. then. else, case and shell loops etc.

Why do we need shell scripts?

There are many reasons to write shell scripts:

• To avoid repetitive work and automation.
• System admins use shell scripting for routine backups.
• System monitoring.
• Adding new functionality to the shell etc.

Some Advantages of shell scripts

• The command and syntax are exactly the same as those directly entered in the command line, so programmers do not need to switch to entirely different syntax
• Writing shell scripts are much quicker.
• Quick start.
• Interactive debugging etc.

Some Disadvantages of shell scripts

• Prone to costly errors, a single mistake can change the command which might be harmful.
• Slow execution speed.
• Design flaws within the language syntax or implementation.
• Not well suited for large and complex task.
• Provide minimal data structure unlike other scripting languages. etc.