Linux 进程通信之FIFO的实现

FIFO通信(first in first out)

FIFO 有名管道,实现无血缘关系进程通信。

  • 创建一个管道的伪文件
    • a.mkfifo testfifo 命令创建
    • b.也可以使用函数int mkfifo(const char *pathname, mode_t mode);
  • 内核会针对fifo文件开辟一个缓冲区,操作fifo文件,可以操作缓冲区,实现进程间通信–实际上就是文件读写

man 3 mkfifo

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

注意事项:

FIFOs
Opening the read or write end of a FIFO blocks until the other end is also opened (by another process or thread). See
fifo(7) for further details.

打开fifo文件时候,read端会阻塞等待write端open,write端同理,也会阻塞等待另外一段打开。

代码示例:
file_w.c 写端

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main(int argc, char *argv[]) {
  if(argc != 2) {
    printf("./a.out filename1\n");
    return -1;
  }
  printf("begin open w\n");
  int o_ret = open(argv[1], O_WRONLY);
  printf("end open w\n");
  char buf[256];
  int num = 0;
  while (1) {
    memset(buf, '\0', sizeof(buf));
    sprintf(buf, "xiaoming--%d", num++);
    printf("strlen(buf) = %d\n", strlen(buf));
    write(o_ret, buf, strlen(buf));
    sleep(1);
  }
  close(o_ret);
  return 0;
}
 

file_r.c 读端

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main(int argc, char *argv[]) {
  if(argc != 2) {
    printf("./a.out filename1\n");
    return -1;
  }
  printf("begin open r\n");
  int o_ret = open(argv[1], O_RDONLY);
  printf("end open r\n");
  char buf[256];
  int num = 0;
  while (1) {
    memset(buf, '\0', sizeof(buf));
    read(o_ret, buf, sizeof(buf));
    printf("strlen(buf) = %d\n", strlen(buf));
    printf("read is%s\n", buf);
  }
  close(o_ret);
  return 0;
}

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