readdir_r(3) - Linux manual page (original) (raw)
readdirr(3) Library Functions Manual readdirr(3)
NAME top
readdir_r - read a directoryLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#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_SOURCEDESCRIPTION top
This function is deprecated; use [readdir(3)](../man3/readdir.3.html) instead.
The **readdir_r**() function was invented as a reentrant version of
[readdir(3)](../man3/readdir.3.html). 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)](../man3/readdir.3.html).
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)](../man3/readdir.3.html) 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
_dname_ field may not be null terminated or may be truncated.
• In the current POSIX.1 specification (POSIX.1-2008), [readdir(3)](../man3/readdir.3.html)
is not required to be thread-safe. However, in modern
implementations (including the glibc implementation),
concurrent calls to [readdir(3)](../man3/readdir.3.html) 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)](../man3/readdir.3.html) 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)](../man3/readdir.3.html) be thread-
safe when concurrently employed on different directory streams.RETURN VALUE top
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_.ERRORS top
**EBADF** Invalid directory stream descriptor _dirp_.
**ENAMETOOLONG**
A directory entry whose name was too long to be read was
encountered.ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ **Interface** │ **Attribute** │ **Value** │
├──────────────────────────────────────┼───────────────┼─────────┤
│ **readdir_r**() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘STANDARDS top
POSIX.1-2008.HISTORY top
POSIX.1-2001.SEE ALSO top
[readdir(3)](../man3/readdir.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 readdirr(3)
Pages that refer to this page:readdir(3)