dirfd - get directory stream file descriptor

       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                                                                   │ Attribute     │ Value   │
       ├─────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │ dirfd()                                                                     │ Thread safety │ MT-Safe │
       └─────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

       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.

       POSIX.1-2008 specifies two errors, neither of which is returned by the current implementation.

       EINVALdirp does not refer to a valid directory stream.

       ENOTSUP
              The implementation does not support the association of a file descriptor with a directory.

       4.3BSD-Reno (not in 4.2BSD).

       Standard C library (libc, -lc)

       dirfd - get directory stream file descriptor

       On success, dirfd() returns a file descriptor (a nonnegative integer).  On error,  -1  is  returned,  and
       errno is set to indicate the error.

open(2), openat(2), closedir(3), opendir(3), readdir(3), rewinddir(3), scandir(3), seekdir(3), telldir(3)

Linux man-pages 6.9.1                              2024-05-02                                           dirfd(3)

       POSIX.1-2008.

#include<sys/types.h>#include<dirent.h>intdirfd(DIR*dirp);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       dirfd():
           /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE