config_test/child_test.c

   1 /* Base code taken from http://www-h.eng.cam.ac.uk/help/tpl/unix/fork.html
   2  * Fix for redhat suggested by Ptere Pramberger, peter@pramberger.at */
   3 #include <unistd.h>
   4 #include <sys/wait.h>
   5 #include <stdio.h>
   6 #include <sys/types.h>
   7 #include <signal.h>
   8 void popen_sigchld_handler (int);
   9 int childtermd;
  10
  11 int main(){
  12  char str[1024];
  13  int pipefd[2];
  14  pid_t pid;
  15  int status, died;
  16
  17         if (signal (SIGCHLD, popen_sigchld_handler) == SIG_ERR) {
  18                 printf ("Cannot catch SIGCHLD\n");
  19                 _exit(-1);
  20         }
  21
  22   pipe (pipefd);
  23   switch(pid=fork()){
  24    case -1:
  25             printf("can't fork\n");
  26             _exit(-1);
  27
  28    case 0 : /* this is the code the child runs */
  29             close(1);      /* close stdout */
  30             /* pipefd[1] is for writing to the pipe. We want the output
  31              * that used to go to the standard output (file descriptor 1)
  32              * to be written to the pipe. The following command does this,
  33              * creating a new file descripter 1 (the lowest available)
  34              * that writes where pipefd[1] goes. */
  35             dup (pipefd[1]); /* points pipefd at file descriptor */
  36             /* the child isn't going to read from the pipe, so
  37              * pipefd[0] can be closed */
  38             close (pipefd[0]);
  39
  40             /* These are the commands to run, with success commented. dig and nslookup only problems */
  41             /*execl ("/bin/date","date",0);*/                   /* 100% */
  42             /*execl ("/bin/cat", "cat", "/etc/hosts", 0);*/     /* 100% */
  43             /*execl ("/usr/bin/dig", "dig", "redhat.com", 0);*/ /* 69% */
  44             /*execl("/bin/sleep", "sleep", "1", 0);*/           /* 100% */
  45             execl ("/usr/bin/nslookup","nslookup","redhat.com",0); /* 90% (after 100 tests), 40% (after 10 tests) */
  46             /*execl ("/bin/ping","ping","-c","1","localhost",0);*/      /* 100% */
  47             /*execl ("/bin/ping","ping","-c","1","192.168.10.32",0);*/  /* 100% */
  48             _exit(0);
  49
  50    default: /* this is the code the parent runs */
  51
  52             close(0); /* close stdin */
  53             /* Set file descriptor 0 (stdin) to read from the pipe */
  54             dup (pipefd[0]);
  55             /* the parent isn't going to write to the pipe */
  56             close (pipefd[1]);
  57             /* Now read from the pipe */
  58             fgets(str, 1023, stdin);
  59             /*printf("1st line output is %s\n", str);*/
  60
  61             /*while (!childtermd);*/  /* Uncomment this line to fix */
  62
  63             died= wait(&status);
  64             /*printf("died=%d status=%d\n", died, status);*/
  65             if (died > 0) _exit(0);
  66             else          _exit(1);
  67    }
  68 }
  69
  70 void
  71 popen_sigchld_handler (int signo)
  72 {
  73         if (signo == SIGCHLD) {
  74                 /*printf("Caught sigchld\n");*/
  75                 childtermd = 1;
  76         }
  77 }