Name
readdir_r — read a directory
Synopsis
#include <dirent.h>
int
readdir_r( |
DIR *dirp, |
| struct dirent *entry, | |
struct dirent **result); |
![[Note]](../stylesheet/note.png) |
Note | |||
|---|---|---|---|---|
|
DESCRIPTION
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
readir(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() instead of readdir_r(). Furthermore, since version
2.24, glibc deprecates readdir_r(). The reasons are as
follows:
-
On systems where
NAME_MAXis undefined, callingreaddir_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 returnedd_namefield 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 ofreaddir_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 thatreaddir() be thread-safe when concurrently employed on different directory streams.
RETURN VALUE
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
- EBADF
-
Invalid directory stream descriptor
dirp. - ENAMETOOLONG
-
A directory entry whose name was too long to be read was encountered.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
readdir_r() |
Thread safety | MT-Safe |
COLOPHON
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description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
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