semaphore shmget() semflg = 384做什么？

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 );

谁能告诉我384的值对semflg有什么影响？

Answer 1

shmget的手册页上写道：

除了上述标志外，shmflg的最低有效的9位指定授予所有者、组和其他人的权限。这些位与open(2)的模式参数具有相同的格式和含义。

让我们来看看打开的手册页

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

整数值384被编码为二进制的110000000，其对应于标志600，即S_IRUSR|S_IWUSR

• 用户对

具有写入权限和读取权限

不管是谁写了这段代码，他节省了2分钟的时间，而浪费了包括我在内的许多其他人的时间。

祝贺你。:)

编辑：感谢@Fabio Turati指出了一个主要错误;)