Section (3) readdir_r
readdir_r — read a directory
|struct dirent *entry,|
|struct dirent **result
This function is deprecated; use readdir(3) instead.
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
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 *
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
On systems where
NAME_MAXis 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_zsingle_quotesz_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_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 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.
returns 0 on success. On error, it returns a positive error
number (listed under ERRORS). If the end of the directory
stream is reached,
returns 0, and returns NULL in *
Invalid directory stream descriptor
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).
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