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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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DIRFD(3P) POSIX Programmer's Manual DIRFD(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
dirfd — extract the file descriptor used by a DIR stream
#include <dirent.h>
int dirfd(DIR *dirp);
The dirfd() function shall return a file descriptor referring to
the same directory as the dirp argument. This file descriptor
shall be closed by a call to closedir(). If any attempt is made
to close the file descriptor, or to modify the state of the
associated description, other than by means of closedir(),
readdir(), readdir_r(), rewinddir(), or seekdir(), the behavior
is undefined.
Upon successful completion, the dirfd() function shall return an
integer which contains a file descriptor for the stream pointed
to by dirp. Otherwise, it shall return -1 and shall set errno to
indicate the error.
The dirfd() function may fail if:
EINVAL The dirp argument does not refer to a valid directory
stream.
The following sections are informative.
None.
The dirfd() function is intended to be a mechanism by which an
application may obtain a file descriptor to use for the fchdir()
function.
This interface was introduced because the Base Definitions volume
of POSIX.1‐2017 does not make public the DIR data structure.
Applications tend to use the fchdir() function on the file
descriptor returned by this interface, and this has proven useful
for security reasons; in particular, it is a better technique
than others where directory names might change.
The description uses the term ``a file descriptor'' rather than
``the file descriptor''. The implication intended is that an
implementation that does not use an fd for opendir() could still
open() the directory to implement the dirfd() function. Such a
descriptor must be closed later during a call to closedir().
If it is necessary to allocate an fd to be returned by dirfd(),
it should be done at the time of a call to opendir().
None.
closedir(3p), fchdir(3p), fdopendir(3p), fileno(3p), open(3p),
readdir(3p)
The Base Definitions volume of POSIX.1‐2017, dirent.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any
discrepancy between this version and the original IEEE and The
Open Group Standard, the original IEEE and The Open Group
Standard is the referee document. The original Standard can be
obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 DIRFD(3P)
Pages that refer to this page: dirent.h(0p), closedir(3p), fchdir(3p), fdopendir(3p), fileno(3p), open(3p), readdir(3p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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