1READDIR_R(3) Linux Programmer's Manual READDIR_R(3)
2
6 readdir_r - read a directory
7
9 #include <dirent.h>
10 int readdir_r(DIR *restrict dirp, struct dirent *restrict entry,
12 struct dirent **restrict result);
13 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
15 readdir_r():
17 _POSIX_C_SOURCE
18 || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
19
21 This function is deprecated; use readdir(3) instead.
22 The readdir_r() function was invented as a reentrant version of read‐
24 dir(3). It reads the next directory entry from the directory stream
25 dirp, and returns it in the caller-allocated buffer pointed to by en‐
26 try. For details of the dirent structure, see readdir(3).
27 A pointer to the returned buffer is placed in *result; if the end of
29 the directory stream was encountered, then NULL is instead returned in
30 *result.
31 It is recommended that applications use readdir(3) instead of read‐
33 dir_r(). Furthermore, since version 2.24, glibc deprecates read‐
34 dir_r(). The reasons are as follows:
35 * On systems where NAME_MAX is undefined, calling readdir_r() may be
37 unsafe because the interface does not allow the caller to specify
38 the length of the buffer used for the returned directory entry.
39 * On some systems, readdir_r() can't read directory entries with very
41 long names. When the glibc implementation encounters such a name,
42 readdir_r() fails with the error ENAMETOOLONG after the final direc‐
43 tory entry has been read. On some other systems, readdir_r() may
44 return a success status, but the returned d_name field may not be
45 null terminated or may be truncated.
46 * In the current POSIX.1 specification (POSIX.1-2008), readdir(3) is
48 not required to be thread-safe. However, in modern implementations
49 (including the glibc implementation), concurrent calls to readdir(3)
50 that specify different directory streams are thread-safe. There‐
51 fore, the use of readdir_r() is generally unnecessary in multi‐
52 threaded programs. In cases where multiple threads must read from
53 the same directory stream, using readdir(3) with external synchro‐
54 nization is still preferable to the use of readdir_r(), for the rea‐
55 sons given in the points above.
56 * It is expected that a future version of POSIX.1 will make read‐
58 dir_r() obsolete, and require that readdir(3) be thread-safe when
59 concurrently employed on different directory streams.
60
62 The readdir_r() function returns 0 on success. On error, it returns a
63 positive error number (listed under ERRORS). If the end of the direc‐
64 tory stream is reached, readdir_r() returns 0, and returns NULL in *re‐
65 sult.
66
68 EBADF Invalid directory stream descriptor dirp.
69 ENAMETOOLONG
71 A directory entry whose name was too long to be read was encoun‐
72 tered.
73
75 For an explanation of the terms used in this section, see at‐
76 tributes(7).
77 ┌────────────────────────────────────────────┬───────────────┬─────────┐
79 │Interface │ Attribute │ Value │
80 ├────────────────────────────────────────────┼───────────────┼─────────┤
81 │readdir_r() │ Thread safety │ MT-Safe │
82 └────────────────────────────────────────────┴───────────────┴─────────┘
83
85 POSIX.1-2001, POSIX.1-2008.
86
88 readdir(3)
89
91 This page is part of release 5.13 of the Linux man-pages project. A
92 description of the project, information about reporting bugs, and the
93 latest version of this page, can be found at
94 https://www.kernel.org/doc/man-pages/.
95 2021-03-22 READDIR_R(3)