test1.c

华清远见应用培训班例程源码

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

int main(int argc, char **argv)
{
  // pid_t fork(void);
  pid_t pid;

  int parent_int_data = 1000;
  char *parent_string_data = "Just a test.\n";

  int i;

  for (i = 0; i < 3; i++)
  {
    fprintf(stdout, "[%d]DEBUG: call fork() %d\n", getpid(), i);

    pid = fork();

    // XXX: Otherwise,  -1  shall  be returned  to  the  parent  process,  no child process shall be created, and errno shall be set to indicate the error.
    if (pid < 0)
    {
      // FIXME: deal with this error.
      fprintf(stderr, "ERROR: call fork() failed: errno=%d, error message: %s\n", errno, strerror(errno));

      switch (errno)
      {
	case EAGAIN:
	  fprintf(stderr, "The error is EAGAIN.\n");
	  break;
	case ENOMEM:
	  fprintf(stderr, "The error is ENOMEM.\n");
	  break;
	default:
	  fprintf(stderr, "Other error.\n");
	  break;
      }

      exit(1);
    }

    // XXX: Upon successful completion, fork() shall return 0 to the child process and  shall return  the process ID of the child process to the parent process. Both processes shall continue to execute from  the  fork()  function.  
    if (pid == 0)
    {
#ifdef _DEBUG_
      fprintf(stdout, "[%d]DEBUG: I'm child process, my pid = %d\n", getpid(), getpid());
      fprintf(stdout, "[%d]DEBUG: My parent pid = %d\n", getpid(), getppid());
      fprintf(stdout, "[%d]DEBUG: current i = %d\n", getpid(), i);
#endif
      fprintf(stdout, "[%d]DEBUG: parent_int_data = %d\n", getpid(), parent_int_data);
      fprintf(stdout, "[%d]DEBUG: parent_string_data = %s\n", getpid(), parent_string_data);

      // XXX: Here call exit() to quit is very important.
      //exit(0);
      //sleep(5);
    }
    else if (pid > 0)
    {
#ifdef _DEBUG_
      fprintf(stdout, "[%d]DEBUG: I'm parent process, my pid = %d, the new created child process pid = %d\n", getpid(), getpid(), pid);
      fprintf(stdout, "[%d]DEBUG: My parent pid = %d\n", getpid(), getppid());
      fprintf(stdout, "[%d]DEBUG: current i = %d\n", getpid(), i);
#endif
      fprintf(stdout, "[%d]DEBUG: parent_int_data = %d\n", getpid(), parent_int_data);
      fprintf(stdout, "[%d]DEBUG: parent_string_data = %s\n", getpid(), parent_string_data);
    }

    // TODO: do something.
  }

  return 0;
}