单实例进程的几种实现方式

2023-05-06

让进程只运行一个实例,防止多次运行导致的问题

linux利用文件锁实现

static int lockfile(int fd)
{
    struct flock fl;

    fl.l_type   = F_WRLCK;
    fl.l_start  = 0;
    fl.l_whence = SEEK_SET;
    fl.l_len    = 0;

    return(fcntl(fd, F_SETLK, &fl));
}

bool proc_is_exist(const char *procname)
{
    int  fd;
    char buf[16];
    char filename[100];
    sprintf(filename, "/tmp/%s.pid", procname);

    fd = open(filename, O_RDWR | O_CREAT, (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH));
    if (fd < 0) {
        printf("open file \"%s\" failed!!!\n", filename);
        return true;
    }

    if (lockfile(fd) == -1) {                                                  /* 尝试对文件进行加锁 */
        printf("file \"%s\" locked. proc already exit!!!\n", filename);
        close(fd);
        return true;
    } else {
        ftruncate(fd, 0);                                                      /* 写入运行实例的pid */
        sprintf(buf, "%ld", (long)getpid());
        write(fd, buf, strlen(buf) + 1);
        return false;
    }
}

windows利用内核对象实现

HANDLE hMutex = ::CreateMutexA(NULL, FALSE, "Protected_Mutex_11");
DWORD dwError = GetLastError();
if (ERROR_ALREADY_EXISTS == dwError || ERROR_ACCESS_DENIED == dwError)
{
	// 已经有实例了，退出。
	return 0;
}

Qt复用共享内存实现

.h QSharedMemory *m_sharedMemory;

bool isInstanceExisted()
{
	m_sharedMemory = new QSharedMemory("protected-client.lock");
	if(m_sharedMemory->create(100) == false) {  
		return true;
	}  
	return false;  
}