how to run a function as root in shell script

Question

I want to make a script and add this to a shortcut launcher...
When i double click the icon, it will popup a terminal window (done)

In the terminal, it will ask for root password at first and then do some stuff with root privilege (I want to make it as a function).

After that, at the end of the script, it will close the window like "press any key to close window" (I can do it)

#!/bin/sh
touchpad(){
    whoami
}
sudo -S touchpad # but it return error "command not found"

How to run a function as root user or is there another way to accomplish this?

EDIT :
I have tried this #!/bin/bash

sudo ./main2.sh #this did not work when I made it as a launcher
exit 

This is my current code (after googling):

#!/bin/bash

gksudo -m "Input Password" clear
sudo whoami
#sudo bla bla bla
read -n 1 -p "Press any key to close window"

This is what I want, but got an error when I type the wrong password for 3 times. How to force quit the main window if gksudo fail??

Answer 1

Test the return value of gksudo:

if ! gksudo -m "Input Password" clear ; then
    echo Bad password
    exit 1
fi

Answer 2

IMHO ... Simplest way to run the entire script as root without having to remember that it needs to be run as root It seems like it should work for what you are trying to accomplish

#!/bin/bash
dScript=$0
if [[ ${UID} -gt 0 ]] ; then
    sudo ${dScript}
    exit
fi
### the rest of your script

Answer 3

You can't. To do it, you need to put the function in another script, and run that script with sudo.

Sudo only runs commands, it cannot access functions inside your script, as it runs in a separate process. If you insist on running a function in your script, you could run the script again with sudo, but pass it an argument with $1 that runs the function directly.

Answer 4

what about using gksudo instead? It will prompt user for entering password. Then it should work with just sudo.

Answer 5

You actually can do that:

Assuming that you are logged in as a root user and you want to run a function for a different user other than root, you can use export -f option in your script for that function. For example:

#!/usr/local/bin/bash

user="${SUDO_USER:-$USER}"
whomomlikes(){
   echo "Hello!! $(whoami)";
}
main()
{
  export -f whomomlikes;
  su $user -c "bash -c whomomlikes";
}
main;

Not that it would only work for the exported function, if you have variables declared in other functions then you have to export them similarly and then run them accordingly.