dirfd - get directory stream file descriptor
int dirfd(DIR *dirp);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
/* Since glibc 2.10: */
_POSIX_C_SOURCE >= 200809L
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
The function dirfd() returns the file descriptor associated with the directory stream dirp.
This file descriptor is the one used internally by the directory stream. As a result, it is useful only for functions which do not depend on or alter the file position, such as fstat(2) and fchdir(2). It will be automatically closed when closedir(3) is called.
On success, dirfd() returns a file descriptor (a nonnegative integer). On error, -1 is returned, and errno is set to indicate the cause of the error.
POSIX.1-2008 specifies two errors, neither of which is returned by the current implementation.
dirp does not refer to a valid directory stream.
The implementation does not support the association of a file descriptor with a directory.
For an explanation of the terms used in this section, see attributes(7).
POSIX.1-2008. This function was a BSD extension, present in 4.3BSD-Reno, not in 4.2BSD.
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