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.
C
<lang c>#include<stdio.h>
- 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
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
<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
- 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")