How to declare shell functions in UNIX/Linux
We use the function keyword to declare functions in UNIX/Linux, as shown below:
_functionName_()
{
//function body
}
_functionName_: name of the function.function body: statements written within a function.
Call a function
To call a function, write its name where you want to call the function:
_functionName_
Add input parameters
To add input parameters to a function, write the parameters after the name of the function where it is called:
_functionName_ _param1_ _param2_
_param1_ and _param2_ are the input parameters.
Return value
To return a value from a function, use the return keyword followed by the return value.
Note: The function will not execute any statements written in the function after the return statement.
Example 1
Consider the code snippet below, which demonstrates the implementation of a simple function to print “Hello world!!” on screen.
printFunction () {echo "Hello world!!"}printFunction #calling the function
Example 2
Consider this example of a function that takes input parameters.
greetFunction () {echo "Hello $1!! How are you?"}greetFunction Ali #calling the function
Ali is the input parameter to the function greetFunction. ＄1 in line 2 is used to reference the value of the input parameter.
Example 3
Consider this example of a function that takes two numbers and returns their sum.
sumFunction () {return $(($1+$2))}sumFunction 2 5 #calling the functionsum=$? #getting return value of functionecho "2 + 5 = $sum"
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