可能是
umask。
援引的手册页
shm_open：
O_CREAT Create the shared memory object if it does not exist. The user and group ownership of the object are taken from the corresponding effec‐ tive IDs of the calling process, and the object's permission bits are set according to the low-order 9 bits of mode, except that those bits set in the process file mode creation mask (see umask(2)) are cleared for the new object. A set of macro constants which can be used to define mode is listed in open(2). (Symbolic definitions of these constants can be obtained by including <sys/stat.h>.)
因此，为了允许创建可全局写入的文件，您需要设置允许它的umask，例如：
umask(0);
进行这样的设置，
umask将不再影响已创建文件的任何权限。但是，您应该注意，如果您随后创建另一个文件而未明确指定权限，那么该文件也是可写的。
因此，您可能只想暂时清除umask，然后将其还原：
#include <sys/types.h>#include <sys/stat.h>...void yourfunc(){ // store old mode_t old_umask = umask(0); int fd = shm_open(SHARE_MEM_NAME,O_RDWR | O_CREAT,0606); // restore old umask(old_umask);}
