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 *dirp, struct dirent ***namelist,
13 int (*filter)(const struct dirent *),
14 int (*compar)(const struct dirent **, const struct dirent **));
15 int alphasort(const struct dirent **a, const struct dirent **b);
17 int versionsort(const struct dirent **a, const struct dirent **b);
19 #include <fcntl.h> /* Definition of AT_* constants */
21 #include <dirent.h>
22 int scandirat(int dirfd, const char *dirp, struct dirent ***namelist,
24 int (*filter)(const struct dirent *),
25 int (*compar)(const struct dirent **, const struct dirent **));
26 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
28 scandir(), alphasort():
30 /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
31 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
32 versionsort(): _GNU_SOURCE
34 scandirat(): _GNU_SOURCE
36
38 The scandir() function scans the directory dirp, calling filter() on
39 each directory entry. Entries for which filter() returns nonzero are
40 stored in strings allocated via malloc(3), sorted using qsort(3) with
41 the comparison function compar(), and collected in array namelist which
42 is allocated via malloc(3). If filter is NULL, all entries are
43 selected.
44 The alphasort() and versionsort() functions can be used as the compari‐
46 son function compar(). The former sorts directory entries using str‐
47 coll(3), the latter using strverscmp(3) on the strings (*a)->d_name and
48 (*b)->d_name.
49 scandirat()
51 The scandirat() function operates in exactly the same way as scandir(),
52 except for the differences described here.
53 If the pathname given in dirp is relative, then it is interpreted rela‐
55 tive to the directory referred to by the file descriptor dirfd (rather
56 than relative to the current working directory of the calling process,
57 as is done by scandir() for a relative pathname).
58 If dirp is relative and dirfd is the special value AT_FDCWD, then dirp
60 is interpreted relative to the current working directory of the calling
61 process (like scandir()).
62 If dirp is absolute, then dirfd is ignored.
64 See openat(2) for an explanation of the need for scandirat().
66
68 The scandir() function returns the number of directory entries
69 selected. On error, -1 is returned, with errno set to indicate the
70 cause of the error.
71 The alphasort() and versionsort() functions return an integer less
73 than, equal to, or greater than zero if the first argument is consid‐
74 ered to be respectively less than, equal to, or greater than the sec‐
75 ond.
76
78 ENOENT The path in dirp does not exist.
79 ENOMEM Insufficient memory to complete the operation.
81 ENOTDIR
83 The path in dirp is not a directory.
84 The following additional errors can occur for scandirat():
86 EBADF dirfd is not a valid file descriptor.
88 ENOTDIR
90 dirp is a relative path and dirfd is a file descriptor referring
91 to a file other than a directory.
92
94 versionsort() was added to glibc in version 2.1.
95 scandirat() was added to glibc in version 2.15.
97
99 For an explanation of the terms used in this section, see
100 attributes(7).
101 ┌───────────────────────────┬───────────────┬────────────────┐
103 │Interface │ Attribute │ Value │
104 ├───────────────────────────┼───────────────┼────────────────┤
105 │scandir(), scandirat() │ Thread safety │ MT-Safe │
106 ├───────────────────────────┼───────────────┼────────────────┤
107 │alphasort(), versionsort() │ Thread safety │ MT-Safe locale │
108 └───────────────────────────┴───────────────┴────────────────┘
109
111 alphasort(), scandir(): 4.3BSD, POSIX.1-2008.
112 versionsort() and scandirat() are GNU extensions.
114
116 Since glibc 2.1, alphasort() calls strcoll(3); earlier it used str‐
117 cmp(3).
118 Before glibc 2.10, the two arguments of alphasort() and versionsort()
120 were typed as const void *. When alphasort() was standardized in
121 POSIX.1-2008, the argument type was specified as the type-safe const
122 struct dirent **, and glibc 2.10 changed the definition of alphasort()
123 (and the nonstandard versionsort()) to match the standard.
124
126 The program below prints a list of the files in the current directory
127 in reverse order.
128 Program source
130 #define _DEFAULT_SOURCE
132 #include <dirent.h>
133 #include <stdio.h>
134 #include <stdlib.h>
135 int
137 main(void)
138 {
139 struct dirent **namelist;
140 int n;
141 n = scandir(".", &namelist, NULL, alphasort);
143 if (n == -1) {
144 perror("scandir");
145 exit(EXIT_FAILURE);
146 }
147 while (n--) {
149 printf("%s\n", namelist[n]->d_name);
150 free(namelist[n]);
151 }
152 free(namelist);
153 exit(EXIT_SUCCESS);
155 }
156
158 closedir(3), fnmatch(3), opendir(3), readdir(3), rewinddir(3),
159 seekdir(3), strcmp(3), strcoll(3), strverscmp(3), telldir(3)
160
162 This page is part of release 5.07 of the Linux man-pages project. A
163 description of the project, information about reporting bugs, and the
164 latest version of this page, can be found at
165 https://www.kernel.org/doc/man-pages/.
166GNU 2020-06-09 SCANDIR(3)