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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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readdir_r(3) Library Functions Manual readdir_r(3)
readdir_r - read a directory
Standard C library (libc, -lc)
#include <dirent.h>
[[deprecated]] int readdir_r(DIR *restrict dirp,
struct dirent *restrict entry,
struct dirent **restrict result);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
readdir_r():
_POSIX_C_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
This function is deprecated; use readdir(3) instead.
The readdir_r() function was invented as a reentrant version of
readdir(3). It reads the next directory entry from the directory
stream dirp, and returns it in the caller-allocated buffer
pointed to by entry. For details of the dirent structure, see
readdir(3).
A pointer to the returned buffer is placed in *result; if the end
of the directory stream was encountered, then NULL is instead
returned in *result.
It is recommended that applications use readdir(3) instead of
readdir_r(). Furthermore, since glibc 2.24, glibc deprecates
readdir_r(). The reasons are as follows:
• On systems where NAME_MAX is undefined, calling readdir_r()
may be unsafe because the interface does not allow the caller
to specify the length of the buffer used for the returned
directory entry.
• On some systems, readdir_r() can't read directory entries with
very long names. When the glibc implementation encounters
such a name, readdir_r() fails with the error ENAMETOOLONG
after the final directory entry has been read. On some other
systems, readdir_r() may return a success status, but the
returned d_name field may not be null terminated or may be
truncated.
• In the current POSIX.1 specification (POSIX.1-2008),
readdir(3) is not required to be thread-safe. However, in
modern implementations (including the glibc implementation),
concurrent calls to readdir(3) that specify different
directory streams are thread-safe. Therefore, the use of
readdir_r() is generally unnecessary in multithreaded
programs. In cases where multiple threads must read from the
same directory stream, using readdir(3) with external
synchronization is still preferable to the use of readdir_r(),
for the reasons given in the points above.
• It is expected that a future version of POSIX.1 will make
readdir_r() obsolete, and require that readdir(3) be thread-
safe when concurrently employed on different directory
streams.
The readdir_r() function returns 0 on success. On error, it
returns a positive error number (listed under ERRORS). If the
end of the directory stream is reached, readdir_r() returns 0,
and returns NULL in *result.
EBADF Invalid directory stream descriptor dirp.
ENAMETOOLONG
A directory entry whose name was too long to be read was
encountered.
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├─────────────────────────────────────┼───────────────┼─────────┤
│ readdir_r() │ Thread safety │ MT-Safe │
└─────────────────────────────────────┴───────────────┴─────────┘
POSIX.1-2008.
POSIX.1-2001.
readdir(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
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2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
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Linux man-pages 6.9.1 2024-05-02 readdir_r(3)
Pages that refer to this page: readdir(3)
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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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