Linux Shell Script Function

 Functions are set of statements which is invoked whenever it is required. In the below example, I am defining 3 functions and invoking them as per the user's choice.

changeHomedir() {

        echo "I am changing the directory to /home/vagrant"

        cd /home/vagrant

        pwd

}

finduser() {

        var1=`whoami`

        echo "You are currently logged in by $var1"

}

patchprocess(){

        echo "This is patch process"

}

choice="Y"

while [ $choice == "Y" ]

do

  echo "1 Change the directory"

  echo "2 Find the logged in user"

  echo "3 Path process"

  echo "4 Exit"

  echo "Enter your choice"

  read choice1

  case $choice1 in

          1)

            changeHomedir

            ;;

          2)

            finduser

            ;;

          3)

            patchprocess

            ;;

          *)

            choice="N"

   esac

done

Function with parameter

We can pass the parameters to the funciton which is represented by $n where n is the argument number.

Example

executecmd() {

        echo "Executing $1 commad"

        $1

}

executecmd $1

In this example $1 which is in the executecmd definition is first parameter of function whereas execute $1 statement $1 is the command line argument

Execute

./func1.sh pwd

Example

Function with parameter and return a value

func1(){

        echo "-------------- $1 process $2---------"

}

func2(){

        var1=`cat $1 | wc -l`

        return $var1

}

func1 "pwd" "starting"

pwd

func1 "pwd" "ending"

func1 "$1" "starting"

$1

func1 "$1" "ending"

func2 $2

echo $?

Execute

./fun1.sh whoami fun1.sh