Test flock

semaphore.cpp

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/sem.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/sem.h>
#include <sys/ipc.h>
#include <iostream>

static int sem_id = 0;

static int semaphore_p()
{
    // 对信号量做减1操作，即等待P（sv）
    struct sembuf sem_b;
    sem_b.sem_num = 0;
    sem_b.sem_op = -1;//P()
    sem_b.sem_flg = SEM_UNDO;
    if (semop(sem_id, &sem_b, 1) == -1)
    {
        fprintf(stderr, "semaphore_p failed\n");
        return 0;
    }

    return 1;
}

static int semaphore_v()
{
    struct sembuf sem_b;
    sem_b.sem_num = 0;
    sem_b.sem_op = 1; // V()
    sem_b.sem_flg = SEM_UNDO;
    if (semop(sem_id, &sem_b, 1) == -1)
    {
        fprintf(stderr, "semaphore_v failed\n");
        return 0;
    }

    return 1;
}

void lockUnLock() {
  sem_id = semget((key_t) 1234, 1, 0666 | IPC_CREAT);

  int i = 0;
  semaphore_p();

  std::cout << "The file was locked " << std::endl;
  std::cout << "please input a number to unlock the file " << std::endl;

  scanf("%d", &i);
  semaphore_v();
}

int main() {
  lockUnLock();
  return 0;
}

test_flock.cpp

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>

#include <iostream>

void lockUnLock() {
  int fd, i;
  char path[] = "test.txt";
  fd = open(path, O_WRONLY | O_CREAT);
  if (fd != -1) {
    std::cout << "open file " << path << std::endl;
    std::cout << "Please input a number to lock the file" << path << std::endl;
    scanf("%d", &i);
    if (flock(fd, LOCK_EX) == 0) {
      std::cout << "The file was locked " << std::endl;
    } else {
      std::cout << "The file was not locked " << std::endl;
    }
    std::cout << "please input a number to unlock the file " << std::endl;
    scanf("%d", &i);
    if (flock(fd, LOCK_UN) == 0) {
      std::cout << "The file was unlocked. " << std::endl;
    } else {
      std::cout << "The file was no unlocked. " << std::endl;
    }
    close(fd);
  } else {
    std::cout << "Cannot open file " << path << std::endl;
  }
}

int main() {
  lockUnLock();
  return 0;
}