Prallel function with different shell ids

Shell Programming and Scripting
1

Hi,
I have a script as follows

func1()
{
echo $$
}

func1
func1

This returns the id of the current shell twice so outputs:
4201
4201

I'd like to change this script so the function is called in a different subshell each time, giving a different shell id for each function call.
i.e. output will be something like:
4201
4204
Does anyone know how I can do this? Is there a way to execute a function in a seperate subshell? Or, can I open a new subshell, call the function and then exit back to the parent shell all from within the script??

I could put the function into a seperate new script and then run this script twice from my original script. This would run the new script in a new subshell. However I would rather keep the code in the original script if possible.

Thanks in advance,
Andy

2

You cannot call a function across shell, but you always have the option to open a sub shell in your script and execute the script again. Be cautious while doing so or you can end up writing a recursive function.

regards
Apoorva Kumar

3

I feared that might be the answer.

Having looked about a bit, I thought that:

echo $$
(echo $$)

would produce different spids as one is run in a subshell. However this outputs the same for both. Any idea why that is the case??

Cheers,
Andrew

4

It's because you are calling a comelete command not a funtion. What was asked in the original post was something like calling a function across shells, which doesnot seems to be possible as a sub shell will not be aware of the function.

regards
Apoorva Kumar

5

Seems that the shell does'nt update the value of $$
The following code x.sh :

func1()
{
  (
     ps -f
     echo $$
  )
}
func1
func1

gives the ouput :

     UID   PID  PPID   C    STIME    TTY  TIME CMD
  gssjgu 27864 30168   1 14:30:55  pts/3  0:00 ps -f 
  gssjgu 30168 32486   0 14:30:55  pts/3  0:00 sh x.sh 
  gssjgu 32486 34188   1 14:30:55  pts/3  0:00 sh x.sh 
  gssjgu 34188 27930   0   Aug 09  pts/3  0:01 -ksh 
32486
     UID   PID  PPID   C    STIME    TTY  TIME CMD
  gssjgu 27866 30170   1 14:30:55  pts/3  0:00 ps -f 
  gssjgu 30170 32486   0 14:30:55  pts/3  0:00 sh x.sh 
  gssjgu 32486 34188   1 14:30:55  pts/3  0:00 sh x.sh 
  gssjgu 34188 27930   0   Aug 09  pts/3  0:01 -ksh 
32486

The pid displayed is the same 32486 but the echo command is executed in two different subshells of which the pid is displayed as the parent pid of the ps command.

Jean-Pierre.

6

Do you know if it is possible to open a new shell from within the script which you can perform the echo and then exit back to the parent?

I tried

ksh
echo $$
exit
echo $$

But it never exits back to the parent.

Thanks for your replies by the way.

Andy

7

This may be little ugly, but what you want to achive can be done this way also .......

say we have one file 'file1' which has only one line 'echo $$'.
We have another file 'file2' which is.....
echo $$
sh file1

if you execute the file2 you will get the desirable.

regards
Apoorva Kumar