Unix Tutorial 13 : Functions

Syntax for defining functions:

function_name()
{
 …
 <statements>
 …
}

To invoke a function, simply use the function name as a command.

Example:

$ function_name

To pass parameters to the function, add space separated arguments like other commands.

Example:

$ function_name $arg1 $arg2 $arg3

The passed parameters can be accessed inside the function using the standard positional variables i.e. $0, $1, $2, $3 etc.

Example:

function_name()
{
 …
 c = $1 + $2
 …
}

Functions can return values using any one of the three methods:

#1) Change the state of a variable or variables.

#2) Use the return command to end the function and return the supplied value to the calling section of the shell script.

Example:

function_name()
{
 echo “hello $1”
 return 1
}

Running the function with a single parameter will echo the value.

$ function_name ram
hello ram

Capturing the return value (stored in $?) as follows:

$ echo $?
1

#3) Capture the output echoed to the stdout.

Example:

$ var = `function_nameram`
$ echo $var
hello ram

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