Call a function using nohup

Question

I am trying to call a function using nohup like this:

function1(){
    while true 
    do
        echo \"function1\"
        sleep 1
    done
}
         


        

Answer 1

Since nohup must be supplied with a filename not a function as a workaround this is what can be done:

function1(){
    while true 
    do
        echo "function1"
        sleep 1
    done

}

echo "$@" | grep -q -- "--nohup" && function1 || nohup $0 "$@" --nohup & 

So when this script gets called with the current arguments:

• `echo "$@" | grep -q -- "--nohup" will return an error status so
• nohup $0 "$@" --nohup & will be invoked, which will invoke this script passing the current arguments and a new argument --nohup

And when this script is called with argument --nohup

• `echo "$@" | grep -q -- "--nohup" will return with zero status (success) so
• function1 will be invoked

Answer 2

Another solution:

function background {
    echo TEST
}
export -f background 

nohup bash -c background &

Answer 3

Yes ! It is possible however tricky, and strictly bash > v2 compatible :

function1(){ local msg=${*:-function1}; echo msg=$msg; }
nohup -- sh -c "$(typeset -f function1); function1 MESSAGE" >nohup.log 2>&1 0</dev/null &

And don't forget "typeset" is bash deprecated in favor of "declare" (though I don't entirely agree with this).

Answer 4

I find a working solution for me - define the function in a file (e.g. .functions) then run the function with nohup:

nohup bash -c "source .functions; function1" &

Tested on Ubuntu 13.04.

Answer 5

nohup applies to commands and not to script functions.

For example, the script (say func.sh) that contains function1() should call the function-:

function1(){
    while true 
    do
        echo "function1"
        sleep 1
    done

}

function1

Now call the script func.sh with nohup in the background-:

nohup ./func.sh &

If you need to disable the hangup signal from within the script use the shell built-in trap. The example ignores SIGHUP but can be used to ignore others (e.g. SIGINT).

trap "" HUP   # script will ignore HANGUP signal

Answer 6

Instead of using nohup, which is tailored for files, you can implement the same result like this:

(trap '' HUP INT
 while true
 do
   echo "function1"
   sleep 1
 done
) </dev/null 2>&1 1>nohup.out &

As I tend to launch these processes from a parent script and the parent script may do other work if the parent process is interrupted I want the child process to ignore the INT signal and keep on running.