linux 下多線程給文件加排他鎖
利用flock 函數，具體用戶請自己查。
執行流程
1，創建 /dev/shm/test文件，並打開文件。
2，fork 一個子進程
在子進程中再次打開文件，目的是不和父進程使用不一樣的文件描述符。
3，父子進程各自給文件加排他鎖並sleep10秒，
然后向文件中寫入數據。
代碼如下
1 /* slock.c */ 2 #include <unistd.h> 3 #include <fcntl.h> 4 #include <sys/types.h> 5 #include <sys/stat.h> 6 #include <string.h> 7 #include <stdio.h> 8 int main() 9 { 10 11 int fd = open( "/dev/shm/test",O_CREAT|O_RDWR,S_IRWXU|S_IRGRP|S_IWGRP|S_IRWXO ); 12 if ( fd < 0 ) 13 { 14 puts( "open error" ); 15 return -1; 16 } 17 if (fork () == 0) { 18 int fd1 = open( "/dev/shm/test",O_RDWR); 19 if(flock(fd1,LOCK_EX)==0){ 20 printf("pid(%d) %s",getpid(), "the file was locked by child .\n"); 21 puts( "child sleep now ..." ); 22 sleep( 10 ); 23 write(fd, "child\n",strlen("child\n")); 24 if(flock(fd1,LOCK_UN)==0){ 25 puts("child the file was unlocked .\n"); 26 } 27 } 28 close( fd1); 29 puts( "child exit..." ); 30 31 } else { 32 if(flock(fd,LOCK_EX)==0){ 33 printf("pid(%d) %s",getpid(), "the file was locked by parent .\n"); 34 puts( "parent sleep now ..." ); 35 sleep( 10 ); 36 write(fd, "parent\n",strlen("parent\n")); 37 if(flock(fd,LOCK_UN)==0){ 38 puts("parent the file was unlocked .\n"); 39 } 40 } 41 42 puts( "parent exit..." ); 43 close( fd ); 44 } 45 return 0;
46 }
執行結果
[root@centos]# ./slockc
pid(1516) the file was locked by parent .
parent sleep now ...
parent the file was unlocked .
parent exit...
[root@centos]# pid(1517) the file was locked by child .
child sleep now ...
child the file was unlocked .
child exit...
最后查看 /dev/shm/test內容
parent
child