C: Linux C 编程 - 命名管道

命名管道

mkfifo

函数原型

int mkfifo(const char *pathname, mode_t mode);

 

mkfifo

Usage: mkfifo [OPTION]... NAME...

Create named pipes (FIFOs) with the given NAMEs.

 

# mkfifo tmp.txt

# file tmp.txt 

tmp.txt: fifo (named pipe)

# ll tmp.txt 

prw-r--r--. 1 root root 0 Oct  7 14:43 tmp.txt

 

# mkfifo -m ugo+rwx tmp_ugo+rwx.txt

# ll tmp_ugo+rwx.txt 

prwxrwxrwx. 1 root root 0 Oct  7 14:44 tmp_ugo+rwx.txt

 

# mkfifo -m a+rwx tmp_a+rwx.txt

# ll tmp_a+rwx.txt 

prwxrwxrwx. 1 root root 0 Oct  7 14:45 tmp_a+rwx.txt

 

# mkfifo -m 0777 tmp_0777.txt

# ll tmp_0777.txt 

prwxrwxrwx. 1 root root 0 Oct  7 14:45 tmp_0777.txt

 

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <unistd.h>
#include <errno.h>

#define INITIALIZED_BUFFER_SIZE 8

int main(int argc, char **argv)
{
  char *file = NULL;
  int fd;
  int daemon = 0;
  int i;
  int n = 0;
  
  for (i = 1; i < argc; i++)
  {
    if (! strcmp(argv[i], "-d"))
    {
      daemon = 1;
    }
    else if (! strncmp(argv[i], "--channel=", 10))
    {
      file = argv[i] + 10;
    }
    else if (! strncmp(argv[i], "--request-count=", 16))
    {
      char *p = argv[i] + 16;
      n = atoi(p);
    }
  }
  if (! file)
  {
    printf("no file.\n");
    return -1;
  }
  if (daemon)
  {
    printf("daemon.\n");
  }

  // if is's daemon, acts as server to reading request 
  // data from clients.
  if (daemon)
  {
    int rb_size = INITIALIZED_BUFFER_SIZE;
    char *rb = (char *) malloc(rb_size);
    int r_offs = 0;
    fd = open(file, O_RDONLY);
    if (fd == -1)
    {
      printf("file: open err.\n");
      return -1;
    }
    printf("file: %s open ok.\n", file);

    while (1)
    {
      int nbytes = read(fd, rb + r_offs, rb_size - r_offs);
      /*
      if (nbytes == 0)
      {
        continue;
      }
      */
      if (nbytes != -1)
      {
        if (nbytes == 0)
        {
          printf("read: eof.\n");
          free(rb);
          break;
        }
        printf("read: %d bytes read, read buffer=%.*s\n", nbytes, rb_size, rb);
        
        
        for (i = r_offs; i < r_offs + nbytes; i++)
        {
          // one request read
          if (rb[i] == '\n')
          {
            printf("---req---:start\n");
            printf("%.*s\n", i + 1, rb);
            printf("---req---:end\n");
            break;
          }
        }
        if (i >= r_offs + nbytes)
        {
          r_offs += nbytes;
          if (r_offs >= rb_size)
          {
            rb_size += INITIALIZED_BUFFER_SIZE;
            rb = realloc(rb, rb_size);
          }
        }
        else
        {
          int offs = i + 1;
          memmove(rb, rb + offs, rb_size - offs);
          r_offs = r_offs + nbytes - offs;
        }
      }
      else
      {
        printf("read: err.\n");
      }
    }
  }
  // else, acts as a client to writing request data to server.
  else 
  {
    char *req = "hello, c\n";
    int nbytes;
    fd = open(file, O_WRONLY);
    if (fd == -1)
    {
      printf("file: open err.\n");
      return -1;
    }
    printf("file: %s open ok.\n", file);

    for (i = 0; i < n; i++)
    {
      nbytes = write(fd, req, strlen(req));
      printf("write: %d bytes writed.\n", nbytes);
    }
  }
  close(fd);
}