shmget返回值问题

xumn56

程序中调用shmget，结果返回值总是0，是什么原因，盼赐教

gawk

RETURN VALUES

  Upon successful completion, a shared memory identifier is returned.  If the
  shmget() function fails, a value of -1 is returned and errno is set to
  indicate the error.
ERRORS

  The shmget() function sets errno to the specified values for the following
  conditions:

  [EACCES]
      A shared memory region ID already exists for the key parameter, but
      operation permission as specified by the low-order nine bits of the
      flags parameter was not granted.

  [EEXIST]
      A shared memory region ID already exists for the key parameter, but
      IPC_CREAT and IPC_EXCL were specified for the flags parameter.

  [EINVAL]
      The value of the size parameter is less than the system-defined minimum
      or greater than the system-defined maximum. Or, a shared memory region
      ID already exists for the key parameter, but the number of bytes allo-
      cated for the region is less than size and size is not equal to 0
      (zero).

  [ENOENT]
      A shared memory region ID does not exist for the key parameter, and
      IPC_CREAT was not used for the flags parameter.

[ENOMEM]
     An attempt was made to create a shared memory region ID and its associ-
     ated shmid_ds structure, but there was not enough physical memory
     available.

[ENOSPC]
     An attempt to create a new shared memory region ID exceeded the
     system-wide limit on the maximum number of IDs allowed.

检查一下

xumn56

谢谢gawk。不过函数没有返回-1，而是返回0，表面上没有错误，然而shmid为0的话实际还是不可用的，所以比较困惑，什么情况下会返回0呢？

net_robber

单从0来判断，不能判断为错误


我遇到过0

手动删除share memory后，你会发现这个值有变化

另外，注意权限