Linux source command (shell function library) [Basic Guide]

The source command is used to read a library file with various functions to the shell in a script file or the command prompt. It searches for library files located in the DIRECTORIES of the PATH variable or a specific file.

Examples:

$ source funcoes.sh $ source /caminho/ate/diretório/funcoes.sh arg1 arg2

In the example below, we will create a file called minhabiblioteca.sh with the following content:

#! /bin/bash

eh_o_root () {
[$ (id -u) -eq 0] && return $TRUE || return $FALSE
}

This file contains a function called “eh_o_root” that returns true if the logged-in user’s uid equals zero (root) or false when it returns another value.

Now let’s create a script called meuscript.sh that will use minhabiblioteca.sh as a function source:

#! /bin/bash 
# Let's read the minhabiblioteca.sh with the command 
source minhabiblioteca.sh 
eh_o_root && echo “You're the Root.” || echo “You're an ordinary user.” 

Now let’s change the permission of meuscript.sh to executable:

$ chmod +x meuscript.sh

When running meuscript.sh:

$. /meuscript.sh 
You are an ordinary user. 

The source command is very useful for reading a library of functions or variables that can be used by various scripts from shell.

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