/* Base code taken from http://www-h.eng.cam.ac.uk/help/tpl/unix/fork.html * Fix for redhat suggested by Ptere Pramberger, peter@pramberger.at */ #include #include #include #include #include void popen_sigchld_handler (int); int childtermd; int main(){ char str[1024]; int pipefd[2]; pid_t pid; int status, died; if (signal (SIGCHLD, popen_sigchld_handler) == SIG_ERR) { printf ("Cannot catch SIGCHLD\n"); _exit(-1); } pipe (pipefd); switch(pid=fork()){ case -1: printf("can't fork\n"); _exit(-1); case 0 : /* this is the code the child runs */ close(1); /* close stdout */ /* pipefd[1] is for writing to the pipe. We want the output * that used to go to the standard output (file descriptor 1) * to be written to the pipe. The following command does this, * creating a new file descriptor 1 (the lowest available) * that writes where pipefd[1] goes. */ dup (pipefd[1]); /* points pipefd at file descriptor */ /* the child isn't going to read from the pipe, so * pipefd[0] can be closed */ close (pipefd[0]); /* These are the commands to run, with success commented. dig and nslookup only problems */ /*execl ("/bin/date","date",0);*/ /* 100% */ /*execl ("/bin/cat", "cat", "/etc/hosts", 0);*/ /* 100% */ /*execl ("/usr/bin/dig", "dig", "redhat.com", 0);*/ /* 69% */ /*execl("/bin/sleep", "sleep", "1", 0);*/ /* 100% */ execl ("/usr/bin/nslookup","nslookup","redhat.com",0); /* 90% (after 100 tests), 40% (after 10 tests) */ /*execl ("/bin/ping","ping","-c","1","localhost",0);*/ /* 100% */ /*execl ("/bin/ping","ping","-c","1","192.168.10.32",0);*/ /* 100% */ _exit(0); default: /* this is the code the parent runs */ close(0); /* close stdin */ /* Set file descriptor 0 (stdin) to read from the pipe */ dup (pipefd[0]); /* the parent isn't going to write to the pipe */ close (pipefd[1]); /* Now read from the pipe */ fgets(str, 1023, stdin); /*printf("1st line output is %s\n", str);*/ /*while (!childtermd);*/ /* Uncomment this line to fix */ died= wait(&status); /*printf("died=%d status=%d\n", died, status);*/ if (died > 0) _exit(0); else _exit(1); } } void popen_sigchld_handler (int signo) { if (signo == SIGCHLD) { /*printf("Caught sigchld\n");*/ childtermd = 1; } }