请问在哪儿能查到shmget返回的错误代码？（100分）__the_segment_memory_path_not_

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请问在哪儿能查到shmget返回的错误代码？（100分）

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本文导语: 我调用shmget失败，errno是20，现在能够确定的是程序没问题，而是环境问题。系统是Linux | find /usr/include -name "errno.h"|xargs grep 20 还可以在程序中添加perror("shmget")，这样能够显示详细的错误...

我调用shmget失败，errno是20，现在能够确定的是程序没问题，而是环境问题。
系统是Linux

find /usr/include -name "errno.h"|xargs grep 20

还可以在程序中添加perror("shmget")，这样能够显示详细的错误信息。

man shmget

ERRORS

On failure, errno is set to one of the following:

EACCES The user does not have permission to access the shared memory segment, and does not have the

CAP_IPC_OWNER capability.

EEXIST IPC_CREAT | IPC_EXCL was specified and the segment exists.

EINVAL A new segment was to be created and size SHMMAX, or no new segment was to

be created, a segment with given key existed, but size is greater than the size of that seg-

ment.

ENFILE The system limit on the total number of open files has been reached.

ENOENT No segment exists for the given key, and IPC_CREAT was not specified.

ENOMEM No memory could be allocated for segment overhead.

ENOSPC All possible shared memory IDs have been taken (SHMMNI), or allocating a segment of the

requested size would cause the system to exceed the system-wide limit on shared memory

(SHMALL).

EPERM The SHM_HUGETLB flag was specified, but the caller was not privileged (did not have the

CAP_IPC_LOCK capability).

man ftok

RETURN VALUE

On success the generated key_t value is returned. On failure -1 is returned, with errno indicating the

error as for the stat(2) system call.

man 2 stat

ERRORS

EACCES Search permission is denied for one of the directories in the path prefix of path. (See also

path_resolution(2).)

EBADF filedes is bad.

EFAULT Bad address.

ELOOP Too many symbolic links encountered while traversing the path.

ENAMETOOLONG

File name too long.

ENOENT A component of the path path does not exist, or the path is an empty string.

ENOMEM Out of memory (i.e. kernel memory).

ENOTDIR

A component of the path is not a directory.

可见你的错误不是shmget引起的, 因为shmget本般并不会返回ENOTDIR的错误而是ftok引起的.

man shmget

ERRORS
       On failure, errno is set to one of the following:

       EACCES      The user does not have permission to access the shared memory segment, and does not have  the
                   CAP_IPC_OWNER capability.

       EEXIST      IPC_CREAT | IPC_EXCL was specified and the segment exists.

       EINVAL      A  new segment was to be created and size  SHMMAX, or no new segment was to
                   be created, a segment with given key existed, but size is greater than the size of that  seg-
                   ment.

       ENFILE      The system limit on the total number of open files has been reached.

       ENOENT      No segment exists for the given key, and IPC_CREAT was not specified.

       ENOMEM      No memory could be allocated for segment overhead.

       ENOSPC      All  possible  shared  memory  IDs  have  been taken (SHMMNI), or allocating a segment of the
                   requested size would cause the system to  exceed  the  system-wide  limit  on  shared  memory
                   (SHMALL).

       EPERM       The  SHM_HUGETLB  flag  was  specified,  but  the caller was not privileged (did not have the
                   CAP_IPC_LOCK capability).

man ftok
RETURN VALUE
       On  success  the  generated key_t value is returned. On failure -1 is returned, with errno indicating the
       error as for the stat(2) system call.
man 2 stat

ERRORS
       EACCES Search permission is denied for one of the directories in the path  prefix  of  path.   (See  also
              path_resolution(2).)

       EBADF  filedes is bad.

       EFAULT Bad address.

       ELOOP  Too many symbolic links encountered while traversing the path.

       ENAMETOOLONG
              File name too long.

       ENOENT A component of the path path does not exist, or the path is an empty string.

       ENOMEM Out of memory (i.e. kernel memory).

       ENOTDIR
              A component of the path is not a directory.

使用函数strerror（errno）获取可读取的错误编码

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