linux 下多線程寫檔案

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linux 下多線程給檔案加獨佔鎖定

   利用flock 函數，具體使用者請自己查。

  執行流程

1，建立 /dev/shm/test檔案，並開啟檔案。

2，fork 一個子進程

     在子進程中再次開啟檔案，目的是不和父進程使用不一樣的檔案描述符。

3，父子進程各自給檔案加獨佔鎖定並sleep10秒， 

   然後向檔案中寫入資料。

 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

[[email protected]]# ./slockc
pid(1516) the file was locked by parent .
parent sleep now ...
parent the file was unlocked .

parent exit...
[[email protected]]# pid(1517) the file was locked  by child .
child sleep now ...
child the file was unlocked .

child exit...

 

最後查看   /dev/shm/test內容

parent
child

linux 下多線程寫檔案