Implementation of FIFO in Linux process communication

FIFO communication (first in first out)

FIFO named pipe, which enables communication between non-related processes.

Create a pseudo file for a pipe
- a. Create a testfifo command using mkfifo
- b. You can also use the function int mkfifo(const char *pathname, mode_t mode);
The kernel will open a buffer for the fifo file and operate the fifo file. It can operate the buffer and realize inter-process communication - in fact, it is file reading and writing.

man 3 mkfifo

#include <sys/types.h>
#include <sys/stat.h>
int mkfifo(const char *pathname, mode_t mode);

Note:

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.

When opening a fifo file, the read end will block waiting for the write end to open, and the write end will also block waiting for another end to open.

Code example:
file_w.c write end

#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 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 Read side

#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 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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