How to use Function in Bash Scripting

SHELL FUNCTION – In this tutorial, you will learn function in bash script, function in shell script, function in shell script with arguments, shell script function with parameters and return value with examples.

• Shell program supports the function which is used to implement the variables as well as execute the linux commands
• Shell scripts two ways to create a function in linux. They are
  • Without using function keyword
  • With using function keyword.

Syntax 1 – Without using reserved function keyword

• Here no need to use reserved keyword function to create a function
• You can directly create a function by just specifying the user defined name followed by () operator.

Example

Syntax 2 – With using reserved keyword function

Here, function can be defined using the reserved word function.

Example

CALLING FUNCTION

• Shell function can be called using its name only.
• The operation () should not be used while calling the function.

I. EXAMPLE OF SHELL FUNCTION

1. SOURCE CODE

2. OUTPUT

SHELL FUNCTION WITH ARGUMENTS

• Shell function supports the arguments
• The arguments are given after the function name while calling the function
• Each argument is separated by space
• The positional parameters like $1, $2, etc… will receive the values of function arguments inside the function definition.

II. EXAMPLE OF SHELL FUNCTION WITH ARGUMENTS

1. SOURCE CODE

2. OUTPUT

SHELL FUNCTION WITH RETURN STATEMENTS

• Like c language, shell function returns the values
• The return keyword is used to return the values in the shell function
• The returned result of the calling function can be obtained using the special symbol $? (by default, the return values of the function will be stored in the built-in variable $?)

NOTE

• It is important to note that the shell function will return a single value.

III. EXAMPLE OF SHELL FUNCTION WITH RETURN VALUE

1. SOURCE CODE

2. OUTPUT

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