How to write a Linux Script (Shebang)?

About

This page is about the creation of Script in Linux.

They

• can be written in many languages
• does not need an extension
• must be given the execution permission

Syntax (Shebang)

#!/bin/bash 
or
#!/usr/bin/env perl

where the first line called the shebang define the interpreter to run.

• the # is the command
• the exclamation mark (“!”) is affectionately called “bang”
• /bin/bash the path to the interpreter.
• env
  • start a new script without environment variable or
  • used when the script’s interpreter is in a non-standard location

The interpreter is not limited to bash. Scripts can be written in an other language such as:

• When a script’s interpreter is in a non-standard location, it's recommended to use env

#!/usr/bin/env bash

• Csh Shell

#!/bin/csh

• Python,

#!/bin/python

• Perl

#!/bin/perl

• Rscript Rscript

#!/usr/bin/Rscript

• Ruby, PHP, etc, etc.

The shebang is a kernel required syntax (not mandatory from the shell prespective)

Location

According to the FHS, the script may be located:

• in the /bin/ or /usr/bin directory for use by all users
• in the user HOME/bin otherwise