Bash Functions – In this Bash Tutorial, we shall learn about functions in Bash Shell Scripting with the help of syntax and examples.. About Bash Functions. Imagine you are trying to write a function to compare two integers but these integers will be provided by end user as command line argument; So how will function access these integer values for comparison? getopts is a function where it can be used to read specified named parameters and set into the bash variables in a easy way. Why would you need that you ask? This function, prints the first argument it receives. Don’t … # the remaining script arguments can be passed to this function. In general, here is the syntax of passing multiple arguments to any bash script: script.sh arg1 arg2 arg3 … The second argument will be referenced by the $2 variable, the third argument is referenced by $3, .. etc. The following script demonstrates how this works. You don’t put parentheses around the arguments like you might expect from some programming languages. Chapter 9: Functions from the Linux shell scripting wiki. Create a shell script using following code. Passing Arguments in Bash Functions. You can pass arguments to the bash function easily by writing them with double quotes after function name separated by space. To do the same without quotes, they'd do program -p hello_world -tSu, where the function program itself gets three arguments. Put any parameters for a bash function right after the function’s name, separated by whitespace, just like you were invoking any shell script or command. Use this method when a script has to perform a slightly different function depending on the values of the input parameters, also called arguments. You can also put arguments without double quotes but in case of spaces used inside the argument, you should use double-quotes. man page – bash Please support my work on Patreon or with a donation. Get the latest tutorials on Linux, Open Source & DevOps via: Passing multiple arguments to a bash shell script. test.sh #!/usr/bin/env bash if [ $# -ge 3 ] then echo script has at least 3 arguments fi produces the following output Bash provides different functions to make reading bash input parameters. Function has to be defined in the shell script first, before you can use it. Arguments could be passed to functions and accessed inside the function as $1, $2 etc. We also have an option to pass input arguments to the bash function. Fig.01: Bash function displaying number of arguments passed to foo() See also. #2. If you want to pass all but the first arguments, you can first use shift to "consume" the first argument and then pass "$@" to pass the remaining arguments to another command. The passing argument to functions is similar to pass an argument to command from shell. Read Bash Parameters with getopts Function. The main difference is the funcion 'e'. 8.2 Functions with parameters sample #!/bin/bash function quit { exit } function e { echo $1 } e Hello e World quit echo foo This script is almost identically to the previous one. $1 only contains one of them, in both Bash and Zsh. To pass all the arguments on, you have to use $@. Functions receives arguments to $1,$2… etc. getopst will read every input parameter and look for the options to match and if match occrus the parameter value set to given variable name. You can pass more than one argument to your bash script. Call bash function with arguments. Bash – Function with Argument. Here is a possible solution that allows you to call a specific function in the script: $ cat functions.sh #!/bin/bash ls2() { echo "Hello World" } ls3() { echo "Testing $*" } # the next line calls the function passed as the first parameter to the script. If you'd like to check if the argument exists, you can check if the # of arguments is greater than or equal to your target argument number. (Or if you want to lock yourself to exactly three arguments, $1 to $3.) Bash Functions. Write a Bash script so that it receives arguments that are specified when the script is called from the command line. Of spaces used inside the argument, you have to use $ @ the arguments like you might from... In a easy way, bash function arguments 'd do program -p hello_world -tSu, where the function itself... T … Call bash function hello_world -tSu, where the function as $ 1 $... Command from shell function has to be defined in the shell script,! The Linux shell scripting wiki quotes, they 'd do program -p hello_world -tSu, where function! Spaces used inside the function as $ 1 only contains one of them, in both and. In the shell script first, before you can pass more than one argument to functions and accessed the... 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