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

int main(int argc, char *argv[]) {
  if(argc != 2) {
    printf("./a.out filename1n");
    return -1;
  }
  printf("begin open wn");
  int o_ret = open(argv[1], O_WRONLY);
  printf("end open wn");
  char buf[256];
  int num = 0;
  while (1) {
    memset(buf, '#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
int main(int argc, char *argv[]) {
if(argc != 2) {
printf("./a.out filename1n");
return -1;
}
printf("begin open wn");
int o_ret = open(argv[1], O_WRONLY);
printf("end open wn");
char buf[256];
int num = 0;
while (1) {
memset(buf, '', sizeof(buf));
sprintf(buf, "xiaoming--%d", num++);
printf("strlen(buf) = %dn", strlen(buf));
write(o_ret, buf, strlen(buf));
sleep(1);
}
close(o_ret);
return 0;
}
', sizeof(buf));
    sprintf(buf, "xiaoming--%d", num++);
    printf("strlen(buf) = %dn", strlen(buf));
    write(o_ret, buf, strlen(buf));
    sleep(1);
  }
  close(o_ret);
  return 0;
}

file_r.c 读端

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

int main(int argc, char *argv[]) {
  if(argc != 2) {
    printf("./a.out filename1n");
    return -1;
  }
  printf("begin open rn");
  int o_ret = open(argv[1], O_RDONLY);
  printf("end open rn");
  char buf[256];
  int num = 0;
  while (1) {
    memset(buf, '#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
int main(int argc, char *argv[]) {
if(argc != 2) {
printf("./a.out filename1n");
return -1;
}
printf("begin open rn");
int o_ret = open(argv[1], O_RDONLY);
printf("end open rn");
char buf[256];
int num = 0;
while (1) {
memset(buf, '', sizeof(buf));
read(o_ret, buf, sizeof(buf));
printf("strlen(buf) = %dn", strlen(buf));
printf("read is%sn", buf);
}
close(o_ret);
return 0;
}
', sizeof(buf));
    read(o_ret, buf, sizeof(buf));
    printf("strlen(buf) = %dn", strlen(buf));
    printf("read is%sn", buf);
  }
  close(o_ret);
  return 0;
}

以上就是本文的全部内容，希望对大家的学习有所帮助。