lock.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/file.h>
#include <errno.h>
#include <string.h>
#define TRUE 1
#define FALSE 0
/**
* @brief 嘗試獲取文件鎖
* @details 獲取文件鎖時(shí)不會(huì)阻塞進(jìn)程, 獲取不到鎖時(shí)膛壹，立即返回不會(huì)等待
* @param fd 文件描述符
* @return 是否成功獲取文件鎖
* @retval TRUE 獲取鎖成功
* @retval FALSE 獲取鎖失敗
* @attention 這里只是建議性鎖誊辉，每個(gè)使用上鎖文件的進(jìn)程都要檢查是否有鎖存在嫉戚，
* 內(nèi)核不對(duì)讀寫(xiě)操作做內(nèi)部檢查和強(qiáng)制保護(hù)
*/
int trylock_fd(int fd)
{
if (flock(fd, LOCK_EX|LOCK_NB) == 0) {
return TRUE;
} else {
return FALSE;
}
}
/**
* @brief 獲取鎖或等待
* @details 獲取文件鎖時(shí)會(huì)阻塞進(jìn)程, 獲取不到鎖時(shí)，一直等到獲取成功
* @param fd 文件描述符
* @return 是否成功獲取文件鎖
* @retval TRUE 獲取鎖成功
* @retval FALSE 獲取鎖失敗
* @attention 這里只是建議性鎖瑰排，每個(gè)使用上鎖文件的進(jìn)程都要檢查是否有鎖存在氧吐，
* 內(nèi)核不對(duì)讀寫(xiě)操作做內(nèi)部檢查和強(qiáng)制保護(hù)
*/
int waitlock_fd(int fd)
{
if (flock(fd, LOCK_EX) == 0) {
return TRUE;
} else {
return FALSE;
}
}
/**
* @brief 釋放文件鎖
* @param fd 文件描述符
* @return 是否成功釋放文件鎖
* @retval TRUE 釋放鎖成功
* @retval FALSE 釋放鎖失敗
*/
int unlock_fd(int fd)
{
if (flock(fd, LOCK_UN) == 0) {
return TRUE;
} else {
return FALSE;
}
}
/**
* @brief 主函數(shù)
* @details 測(cè)試獲取鎖睛藻、釋放鎖的函數(shù)
* @param argc 命令參數(shù)個(gè)數(shù)
* @param argv 命令參數(shù)指針數(shù)組
* @return 程序執(zhí)行成功與否
* @retval 0 程序執(zhí)行成功
* @retval 1 程序執(zhí)行失敗
*/
int main(int argc, char *argv[])
{
int fd;
char *file;
pid_t pid;
if (argc == 2) {
file = argv[1];
} else {
file = "file.lock";
}
pid = getpid();
fd = open(file, O_RDWR|O_CREAT, 0666);
if (fd < 0) {
fprintf(stderr, "failed to open \"%s\", detail: %s(%d)\n",
file, strerror(errno), errno);
exit(1);
}
if(trylock_fd(fd)) {
printf("file has been locked by %d. press any key to unlock\n", pid);
} else {
printf("waiting for lock\n");
waitlock_fd(fd);
printf("file has been locked by %d. press any key to unlock\n", pid);
}
getchar();
unlock_fd(fd);
printf("file has been unlocked by %d.\n", pid);
close(fd);
exit(0);
}
Makefile
CFLAGS= -Wall -O2 -g
OBJS=lock.o
lock: $(OBJS)
gcc -o $@ $(OBJS)
clean:
rm -rf lock $(OBJS) file.lock
編譯
# make
cc -Wall -O2 -g -c -o lock.o lock.c
gcc -o lock lock.o
驗(yàn)證
窗口1
# ./lock
file has been locked by 23791. press any key to unlock
<-- 1) 按任意鍵，釋放鎖
file has been unlocked by 23791.
窗口2
# ./lock
waiting for lock
<-- 等待鎖釋放则北，1)按下任意鍵后繼續(xù)
file has been locked by 23792. press any key to unlock
<-- 2) 按任意鍵，釋放鎖
file has been unlocked by 23792.
