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,
24 struct dirent ***namelist,
25 int (*filter)(const struct dirent *),
26 int (*compar)(const struct dirent **, const struct dirent **));
27 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
29 scandir(), alphasort():
31 /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
32 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
33 versionsort(): _GNU_SOURCE
35 scandirat(): _GNU_SOURCE
37
39 The scandir() function scans the directory dirp, calling filter() on
40 each directory entry. Entries for which filter() returns nonzero are
41 stored in strings allocated via malloc(3), sorted using qsort(3) with
42 the comparison function compar(), and collected in array namelist which
43 is allocated via malloc(3). If filter is NULL, all entries are se‐
44 lected.
45 The alphasort() and versionsort() functions can be used as the compari‐
47 son function compar(). The former sorts directory entries using str‐
48 coll(3), the latter using strverscmp(3) on the strings (*a)->d_name and
49 (*b)->d_name.
50 scandirat()
52 The scandirat() function operates in exactly the same way as scandir(),
53 except for the differences described here.
54 If the pathname given in dirp is relative, then it is interpreted rela‐
56 tive to the directory referred to by the file descriptor dirfd (rather
57 than relative to the current working directory of the calling process,
58 as is done by scandir() for a relative pathname).
59 If dirp is relative and dirfd is the special value AT_FDCWD, then dirp
61 is interpreted relative to the current working directory of the calling
62 process (like scandir()).
63 If dirp is absolute, then dirfd is ignored.
65 See openat(2) for an explanation of the need for scandirat().
67
69 The scandir() function returns the number of directory entries se‐
70 lected. On error, -1 is returned, with errno set to indicate the cause
71 of the error.
72 The alphasort() and versionsort() functions return an integer less
74 than, equal to, or greater than zero if the first argument is consid‐
75 ered to be respectively less than, equal to, or greater than the sec‐
76 ond.
77
79 ENOENT The path in dirp does not exist.
80 ENOMEM Insufficient memory to complete the operation.
82 ENOTDIR
84 The path in dirp is not a directory.
85 The following additional errors can occur for scandirat():
87 EBADF dirfd is not a valid file descriptor.
89 ENOTDIR
91 dirp is a relative path and dirfd is a file descriptor referring
92 to a file other than a directory.
93
95 versionsort() was added to glibc in version 2.1.
96 scandirat() was added to glibc in version 2.15.
98
100 For an explanation of the terms used in this section, see at‐
101 tributes(7).
102 ┌───────────────────────────┬───────────────┬────────────────┐
104 │Interface │ Attribute │ Value │
105 ├───────────────────────────┼───────────────┼────────────────┤
106 │scandir(), scandirat() │ Thread safety │ MT-Safe │
107 ├───────────────────────────┼───────────────┼────────────────┤
108 │alphasort(), versionsort() │ Thread safety │ MT-Safe locale │
109 └───────────────────────────┴───────────────┴────────────────┘
110
112 alphasort(), scandir(): 4.3BSD, POSIX.1-2008.
113 versionsort() and scandirat() are GNU extensions.
115
117 Since glibc 2.1, alphasort() calls strcoll(3); earlier it used str‐
118 cmp(3).
119 Before glibc 2.10, the two arguments of alphasort() and versionsort()
121 were typed as const void *. When alphasort() was standardized in
122 POSIX.1-2008, the argument type was specified as the type-safe const
123 struct dirent **, and glibc 2.10 changed the definition of alphasort()
124 (and the nonstandard versionsort()) to match the standard.
125
127 The program below prints a list of the files in the current directory
128 in reverse order.
129 Program source
131 #define _DEFAULT_SOURCE
133 #include <dirent.h>
134 #include <stdio.h>
135 #include <stdlib.h>
136 int
138 main(void)
139 {
140 struct dirent **namelist;
141 int n;
142 n = scandir(".", &namelist, NULL, alphasort);
144 if (n == -1) {
145 perror("scandir");
146 exit(EXIT_FAILURE);
147 }
148 while (n--) {
150 printf("%s\n", namelist[n]->d_name);
151 free(namelist[n]);
152 }
153 free(namelist);
154 exit(EXIT_SUCCESS);
156 }
157
159 closedir(3), fnmatch(3), opendir(3), readdir(3), rewinddir(3),
160 seekdir(3), strcmp(3), strcoll(3), strverscmp(3), telldir(3)
161
163 This page is part of release 5.10 of the Linux man-pages project. A
164 description of the project, information about reporting bugs, and the
165 latest version of this page, can be found at
166 https://www.kernel.org/doc/man-pages/.
167GNU 2020-06-09 SCANDIR(3)