test2.c

华清远见应用培训班例程源码

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

#define HELLOWORLD	"Hello world!\n"
#define GOODMORNING	"Good morning!"

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

  int x;

  char *p;

  x = 99;

  if ((p = malloc(1024)) == NULL)
  {
    fprintf(stderr, "ERROR: call malloc() to allocate memory failed; %s, errno = %d\n", strerror(errno), errno);
    exit(1);
  }

  memcpy(p, HELLOWORLD, strlen(HELLOWORLD));

  if ((pid = vfork()) < 0)
  {
    // FIXME: handle this fork error
    exit(1);
  }

  fprintf(stdout, "[%d] From here, parent process and child process will execute following section both.\n", getpid());

  //fprintf(stdout, "[%d] x = %d.\n", getpid(), x);
  fprintf(stdout, "[%d] [%d] p = %x.\n", getpid(), time(NULL), p);
  fprintf(stdout, "[%d] [%d] string: %s.\n", getpid(), time(NULL), p);

  if (pid > 0)
  {
    // XXX: Parent process
    // TODO: continue
    fprintf(stdout, "[%d] I'm parent process, the new created child process is %d.\n", getpid(), pid);

    //fprintf(stdout, "[%d] x = %d.\n", getpid(), x);
    fprintf(stdout, "[%d] [%d] p = %x.\n", getpid(), time(NULL), p);
    fprintf(stdout, "[%d] [%d] string: %s.\n", getpid(), time(NULL), p);

#if 0
    if (p)
    {
      free(p);
      p = NULL;
    }
#endif

    memcpy(p, GOODMORNING, strlen(GOODMORNING));

    fprintf(stdout, "[%d] [%d] p = %x.\n", getpid(), time(NULL), p);
    fprintf(stdout, "[%d] [%d] string: %s.\n", getpid(), time(NULL), p);
  }
  else				// pid == 0
  {
    // XXX: child process
    pid_t self_pid, parent_pid;

    self_pid = getpid();
    parent_pid = getppid();

    fprintf(stdout, "[%d] I'm child process, my process id is %d, my parent process id is %d.\n", getpid(), getpid(), getppid());

    sleep(5);

    //fprintf(stdout, "[%d] x = %d.\n", getpid(), x);
    fprintf(stdout, "[%d] [%d] p = %x.\n", getpid(), time(NULL), p);
    fprintf(stdout, "[%d] [%d] string: %s.\n", getpid(), time(NULL), p);


#if 0
    if (p)
    {
      free(p);
      p = NULL;
    }
#endif

    // child process should release all resources allocated by parent process, including opened files, pointers, etc.
    // call exec() to launch a new process
    //exec("ls");
    // call exit() to exit
    exit(0);
    // on exiting, child process will send a SIG_CHILD signal to parent process.
  }

  return 0;
}