Using C to send an exec process to the background?
c, exec, fork, process, unix
Solution
Q: How do I send a process to the background?
A: In general, exactly what you're already doing: fork()/exec().
Q: What's not working as you expect?
I suspect maybe you also want a "nohup" (to completely disassociate the child from the parent).
The key to doing this is to run "setsid()" in the child process:
How to use fork() to daemonize a child process independant of it's parent?
http://www.enderunix.org/docs/eng/daemon.php
Problem
My question sounds the same as this but it isn't: Start a process in the background in Linux with C I know how to do fork() but not how to send a process to the background. My program should work like a simple command unix shell that supports pipes and background processes. I could do pipe and fork but I don't know how to send a process to the background with `&` like the last line of the program: ``` ~>./a.out uname SunOS ^C my:~>./a.out uname & ``` How to achieve the background process? ``` #include <sys/types.h> #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #define TIMEOUT (20) int main(int argc, char *argv[]) { pid_t pid; if(argc > 1 && strncmp(argv[1], "-help", strlen(argv[1])) == 0) { fprintf(stderr, "Usage: Prog [CommandLineArgs]\n\nRunSafe takes as arguments:\nthe program to be run (Prog) and its command line arguments (CommandLineArgs) (if any)\n\nRunSafe will execute Prog with its command line arguments and\nterminate it and any remaining childprocesses after %d seconds\n", TIMEOUT); exit(0); } if((pid = fork()) == 0) /* Fork off child */ { execvp(argv[1], argv+1); fprintf(stderr,"Failed to execute: %s\n",argv[1]); perror("Reason"); kill(getppid(),SIGKILL); /* kill waiting parent */ exit(errno); /* execvp failed, no child - exit immediately */ } else if(pid != -1) { sleep(TIMEOUT); if(kill(0,0) == 0) /* are there processes left? */ { fprintf(stderr,"\Attempting to kill remaining (child) processes\n"); kill(0, SIGKILL); /* send SIGKILL to all child processes */ } } else { fprintf(stderr,"Failed to fork off child process\n"); perror("Reason"); } } ``` The solution in plain English appears to be here: How do I exec() a process in the background in C? Catch SIGCHLD and in the the handler, call wait(). Am I on the right track?