Fork

Fork
You are encouraged to solve this task according to the task description, using any language you may know.

In this task, the goal is to spawn a new process which can run simultaneously with, and independently of, the original parent process.

ALGOL 68

Translation of: C

Works with: ALGOL 68G version Any - tested with release mk15-0.8b.fc9 - "fork" is not part of the standard's preclude.

<lang> main: (

 INT pid;
 IF (pid:=fork)=0 THEN
   print("This is new process")
 ELIF pid>0 THEN
   print("This is the original process")
 ELSE
   print("ERROR: Something went wrong")
 FI

) </lang> Output:

This is new process
This is the original process

C

Works with: gcc

Library: POSIX

<lang c>#include<stdio.h>

1. include<unistd.h>

int main(void) {

 pid_t pid;

 if((pid=fork())==0) {
   printf("This is new process\n");
 } else if(pid>0) {
   printf("This is the original process\n");
 } else {
   printf("ERROR: Something went wrong\n");
 }

 return 0;

}</lang>

Erlang

-module(fork).
-export([start/0]).

start() ->
    spawn(fork,child,[]),
    io:format("This is the original process~n").

child() ->
    io:format("This is the new process~n").

Then you can compile your code and execute it:

c(fork).
fork:start().

OCaml

<lang ocaml>#load "unix.cma";; let pid = Unix.fork ();; if pid > 0 then

 print_endline "This is the original process"

else

 print_endline "This is the new process";;</lang>

Perl

Works with: Perl version 5.x

In the child code, you may have to re-open database handles and such.

<lang perl>FORK: if ($pid = fork()) {

   # parent code

} elsif (defined($pid)) {

   setsid; # tells apache to let go of this process and let it run solo
   # disconnect ourselves from input, output, and errors
   close(STDOUT);
   close(STDIN);
   close(STDERR);    
   # re-open to /dev/null to prevent irrelevant warn messages.
   open(STDOUT, '>/dev/null');
   open(STDIN, '>/dev/null');
   open(STDERR, '>>/home/virtual/logs/err.log');
   
   # child code
   
   exit; # important to exit

} elsif($! =~ /emporar/){

   warn '[' . localtime() . "] Failed to Fork - Will try again in 10 seconds.\n";
   sleep(10);
   goto FORK;

} else {

   warn '[' . localtime() . "] Unable to fork - $!";
   exit(0);

}</lang>

Obviously you could do a Fork in a lot less lines, but this code covers all the bases

Pop11

lvars ress;
if sys_fork(false) ->> ress then
   ;;; parent
   printf(ress, 'Child pid = %p\n');
else
   printf('In child\n');
endif;

Python

Works with: Python version 2.5

<lang python>import os

pid = os.fork() if pid > 0:

# parent code

else:

# child code</lang>

Ruby

<lang ruby>pid = fork if pid

# parent code

else

# child code

end</lang> or <lang ruby>fork do

 # child code

end

1. parent code</lang>

Toka

needs shell
getpid is-data PID
[ fork getpid PID = [ ." Child PID: " . cr ] [ ." In child\n" ] ifTrueFalse ] invoke

UnixPipes

Demonstrating a subshell getting forked, and running concurrently with the original process

(echo "Process 1" >&2 ;sleep 5; echo "1 done" ) | (echo "Process 2";cat;echo "2 done")