1SCANDIR(3) Linux Programmer's Manual SCANDIR(3)
2
6 scandir, scandirat, alphasort, versionsort - scan a directory for
7 matching entries
8
10 #include <dirent.h>
11 int scandir(const char *restrict dirp,
13 struct dirent ***restrict namelist,
14 int (*filter)(const struct dirent *),
15 int (*compar)(const struct dirent **,
16 const struct dirent **));
17 int alphasort(const struct dirent **a, const struct dirent **b);
19 int versionsort(const struct dirent **a, const struct dirent **b);
20 #include <fcntl.h> /* Definition of AT_* constants */
22 #include <dirent.h>
23 int scandirat(int dirfd, const char *restrict dirp,
25 struct dirent ***restrict namelist,
26 int (*filter)(const struct dirent *),
27 int (*compar)(const struct dirent **,
28 const struct dirent **));
29 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
31 scandir(), alphasort():
33 /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
34 || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
35 versionsort():
37 _GNU_SOURCE
38 scandirat():
40 _GNU_SOURCE
41
43 The scandir() function scans the directory dirp, calling filter() on
44 each directory entry. Entries for which filter() returns nonzero are
45 stored in strings allocated via malloc(3), sorted using qsort(3) with
46 the comparison function compar(), and collected in array namelist which
47 is allocated via malloc(3). If filter is NULL, all entries are se‐
48 lected.
49 The alphasort() and versionsort() functions can be used as the compari‐
51 son function compar(). The former sorts directory entries using str‐
52 coll(3), the latter using strverscmp(3) on the strings (*a)->d_name and
53 (*b)->d_name.
54 scandirat()
56 The scandirat() function operates in exactly the same way as scandir(),
57 except for the differences described here.
58 If the pathname given in dirp is relative, then it is interpreted rela‐
60 tive to the directory referred to by the file descriptor dirfd (rather
61 than relative to the current working directory of the calling process,
62 as is done by scandir() for a relative pathname).
63 If dirp is relative and dirfd is the special value AT_FDCWD, then dirp
65 is interpreted relative to the current working directory of the calling
66 process (like scandir()).
67 If dirp is absolute, then dirfd is ignored.
69 See openat(2) for an explanation of the need for scandirat().
71
73 The scandir() function returns the number of directory entries se‐
74 lected. On error, -1 is returned, with errno set to indicate the er‐
75 ror.
76 The alphasort() and versionsort() functions return an integer less
78 than, equal to, or greater than zero if the first argument is consid‐
79 ered to be respectively less than, equal to, or greater than the sec‐
80 ond.
81
83 ENOENT The path in dirp does not exist.
84 ENOMEM Insufficient memory to complete the operation.
86 ENOTDIR
88 The path in dirp is not a directory.
89 The following additional errors can occur for scandirat():
91 EBADF dirfd is not a valid file descriptor.
93 ENOTDIR
95 dirp is a relative path and dirfd is a file descriptor referring
96 to a file other than a directory.
97
99 versionsort() was added to glibc in version 2.1.
100 scandirat() was added to glibc in version 2.15.
102
104 For an explanation of the terms used in this section, see at‐
105 tributes(7).
106 ┌─────────────────────────────────────┬───────────────┬────────────────┐
108 │Interface │ Attribute │ Value │
109 ├─────────────────────────────────────┼───────────────┼────────────────┤
110 │scandir(), scandirat() │ Thread safety │ MT-Safe │
111 ├─────────────────────────────────────┼───────────────┼────────────────┤
112 │alphasort(), versionsort() │ Thread safety │ MT-Safe locale │
113 └─────────────────────────────────────┴───────────────┴────────────────┘
114
116 alphasort(), scandir(): 4.3BSD, POSIX.1-2008.
117 versionsort() and scandirat() are GNU extensions.
119
121 Since glibc 2.1, alphasort() calls strcoll(3); earlier it used str‐
122 cmp(3).
123 Before glibc 2.10, the two arguments of alphasort() and versionsort()
125 were typed as const void *. When alphasort() was standardized in
126 POSIX.1-2008, the argument type was specified as the type-safe const
127 struct dirent **, and glibc 2.10 changed the definition of alphasort()
128 (and the nonstandard versionsort()) to match the standard.
129
131 The program below prints a list of the files in the current directory
132 in reverse order.
133 Program source
135 #define _DEFAULT_SOURCE
137 #include <dirent.h>
138 #include <stdio.h>
139 #include <stdlib.h>
140 int
142 main(void)
143 {
144 struct dirent **namelist;
145 int n;
146 n = scandir(".", &namelist, NULL, alphasort);
148 if (n == -1) {
149 perror("scandir");
150 exit(EXIT_FAILURE);
151 }
152 while (n--) {
154 printf("%s\n", namelist[n]->d_name);
155 free(namelist[n]);
156 }
157 free(namelist);
158 exit(EXIT_SUCCESS);
160 }
161
163 closedir(3), fnmatch(3), opendir(3), readdir(3), rewinddir(3),
164 seekdir(3), strcmp(3), strcoll(3), strverscmp(3), telldir(3)
165
167 This page is part of release 5.12 of the Linux man-pages project. A
168 description of the project, information about reporting bugs, and the
169 latest version of this page, can be found at
170 https://www.kernel.org/doc/man-pages/.
171GNU 2021-03-22 SCANDIR(3)