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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | SEE ALSO | COLOPHON |
READDIR_R(3) Linux Programmer's Manual READDIR_R(3)
readdir_r - read a directory
#include <dirent.h>
int readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
readdir_r():
_POSIX_C_SOURCE
|| /* Glibc versions <= 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 version 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.1-2001, POSIX.1-2008.
readdir(3)
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2016-03-01 READDIR_R(3)
Pages that refer to this page: readdir(3)