test5.1.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 BUFFER_SIZE	1024
#define	FIFO	"/tmp/fifo.test"

void child_process_main(void);
void producer_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);
    }
  }

  producer_process_main();

  //unlink(FIFO);

  return 0;
}

void producer_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);

  sleep(10);

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

  pid_t pid;

  pid = getpid();

  fprintf(stdout, "[%d]Write data to pipe, fd = %d\n", getpid(), fd);

  char buf[BUFFER_SIZE];
  char wbuf[BUFFER_SIZE];

  memset(buf, 0, BUFFER_SIZE);
  // char *fgets(char *restrict s, int n, FILE *restrict stream);
  if (fgets(buf, BUFFER_SIZE, stdin) == NULL)
  {
    fprintf(stdout, "[%d]Read failed from stdin: %s\n", getpid(), strerror(errno));
    // FIXME: handle read from stdin failed
  }
  else
  {
    // ssize_t write(int fildes, const void *buf, size_t nbyte);
    ssize_t n;
    int length;

    length = strlen(buf);
    memset(wbuf, 0, BUFFER_SIZE);

    // int snprintf(char *str, size_t size, const char *format, ...);
    snprintf(wbuf, BUFFER_SIZE, "%08d%s", length, buf);

    fprintf(stdout, "[%d]Composed to-be-sent buffer: %s\n", pid, wbuf);

    n = write(fd, wbuf, strlen(wbuf));

    fprintf(stdout, "[%d]Write %d bytes to pipe.\n", pid, n);
  }

  close(fd);
}