test5.c

这个是学习嵌入式开发的重要例子

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

#define	FIFO	"/tmp/fifo.test"

void child_process_main(void);
void parent_process_main(void);

int main(int argc, char **argv)
{
  umask(0);

  // int mkfifo(const char *path, mode_t mode);
  if (mkfifo(FIFO, 0644) < 0)
  {
    fprintf(stderr, "mkfifo() failed: %s\n", strerror(errno));

    if (errno == EEXIST)
    {
      fprintf(stdout, "The fifo file is alreay existed.\n");
    }
    else
    {
      exit(1);
    }
  }

  pid_t pid;

  if ((pid = fork()) < 0)
  {
    fprintf(stderr, "fork() failed: %s\n", strerror(errno));
    unlink(FIFO);
    exit(1);
  }
  else if (pid == 0)
  {
    // XXX: child process
    //sleep(3);
    child_process_main();
    exit(0);
  }

  parent_process_main();

  unlink(FIFO);

  return 0;
}

void child_process_main(void)
{
  int fd;

  //fd = open(FIFO, O_RDONLY | O_NONBLOCK);
  fd = open(FIFO, O_RDONLY);

  if (fd < 0)
  {
    fprintf(stderr, "[%d]open FIFO %s for reading failed: %s\n", getpid(), FIFO, strerror(errno));
  }
  else
  {
    fprintf(stdout, "[%d]open FIFO %s for reading successed, fd = %d\n", getpid(), FIFO, fd);
    sleep(10);
    close(fd);
  }

  sleep(100);
}

void parent_process_main(void)
{
  int fd;

  //int open(const char *pathname, int flags);
  //int open(const char *pathname, int flags, mode_t mode);
  //fd = open(FIFO, O_WRONLY | O_NONBLOCK);
  fd = open(FIFO, O_WRONLY);

  if (fd < 0)
  {
    fprintf(stderr, "[%d]open FIFO %s for writting failed: %s\n", getpid(), FIFO, strerror(errno));
  }
  else
  {
    fprintf(stdout, "[%d]open FIFO %s for writting successed, fd = %d\n", getpid(), FIFO, fd);
    sleep(10);
    close(fd);
  }
}