semaphore shmget（）semflg = 384是做什麼的？

Question

#include <sys/types.h> 
#include <sys/ipc.h> 
#include <sys/shm.h> 

key_t key = IPC_PRIVATE; 
int id; 
int semflg = 384; 

id = shmget(key, 8192, semflg); 

有人能告訴我什麼影響3844在semflg的價值？

Answer 1

shmget的的手冊頁說：

除了上述標誌， shmflg的至少顯著9位指定授予所有者，組和 其他用戶的權限。這些位具有相同的格式，並且與open（2）的mode參數 具有相同的含義。

因此，讓我們檢查的開放手冊頁：

The following symbolic constants are provided for mode: 
- S_IRWXU 00700 user (file owner) has read, write, and execute permission 
- S_IRUSR 00400 user has read permission 
- S_IWUSR 00200 user has write permission 
- S_IXUSR 00100 user has execute permission 
- S_IRWXG 00070 group has read, write, and execute permission 
- S_IRGRP 00040 group has read permission 
- S_IWGRP 00020 group has write permission 
- S_IXGRP 00010 group has execute permission 
- S_IRWXO 00007 others have read, write, and execute permission 
- S_IROTH 00004 others have read permission 
- S_IWOTH 00002 others have write permission 
- S_IXOTH 00001 others have execute permission 

整數值編碼爲二進制1.1億，對應於標誌，即S_IRUSR|S_IWUSR ：

• 用戶h作爲寫權限
• 用戶具有讀取權限

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誰寫這段代碼倖免2分鐘他的生命，浪費更多的其他許多人的生命的時候，包括我在內。

恭喜。 :)

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編輯：感謝@Fabio圖拉蒂您指出了一個重大錯誤;）