The directory path is created with the access permissions
specified by mode and restricted by the the umask(2) of the
calling process.
The directory's owner ID is set to the process's effective user
ID. The directory's group ID is set to that of the parent directory
in which it is created.
The mkdir(2) call will fail and no directory will be
created if:
[EACCES]
Search permission is denied for a component of the path
prefix.
[EEXIST]
The named file exists.
[EFAULT]
Path points outside the process's allocated address
space.
[EINVAL]
The pathname contains a character with the high-order bit
set.
[EIO]
An I/O error occurred while making the directory entry or
allocating the file serial number.
[EIO]
An I/O error occurred while reading from or writing to the file
system.
[ELOOP]
Too many symbolic links were encountered in translating the
pathname.
[ENAMETOOLONG]
A component of a pathname exceeded {NAME_MAX} characters, or an
entire pathname exceeded {PATH_MAX} characters.
[ENOENT]
A component of the path prefix does not exist.
[ENOSPC]
The new directory cannot be created because there is no space
left on the file system that will contain the directory.
[ENOSPC]
There are no free file serial numbers on the file system on
which the directory is being created.
[ENOSYS]
Operation not applicable. The pathname names a file belonging
to a virtual system that does not exist and cannot be created. For
example, the call mkdir(/Z, mode) will fail with ENOSYS if
drive Z: is not mounted; the call mkdir(/proc/foo,
mode) will fail with ENOSYS because the /proc filesystem
is virtual.
[ENOTDIR]
A component of the path prefix is not a directory.
[EPERM]
The path argument contains a byte with the high-order
bit set.
[EROFS]
The named file resides on a read-only file system.