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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | NOTES | EXAMPLES | SEE ALSO | COLOPHON |
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scandir(3) Library Functions Manual scandir(3)
scandir, scandirat, alphasort, versionsort - scan a directory for
matching entries
Standard C library (libc, -lc)
#include <dirent.h>
int scandir(const char *restrict dirp,
struct dirent ***restrict namelist,
typeof(int (const struct dirent *)) *filter,
typeof(int (const struct dirent **, const struct dirent **))
*compar);
int alphasort(const struct dirent **a, const struct dirent **b);
int versionsort(const struct dirent **a, const struct dirent **b);
#include <fcntl.h> /* Definition of AT_* constants */
#include <dirent.h>
int scandirat(int dirfd, const char *restrict dirp,
struct dirent ***restrict namelist,
typeof(int (const struct dirent *)) *filter,
typeof(int (const struct dirent **, const struct dirent **))
*compar);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
scandir(), alphasort():
/* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
versionsort():
_GNU_SOURCE
scandirat():
_GNU_SOURCE
The scandir() function scans the directory dirp, calling filter()
on each directory entry. Entries for which filter() returns
nonzero are stored in strings allocated via malloc(3), sorted
using qsort(3) with the comparison function compar(), and
collected in array namelist which is allocated via malloc(3). If
filter is NULL, all entries are selected.
The alphasort() and versionsort() functions can be used as the
comparison function compar(). The former sorts directory entries
using strcoll(3), the latter using strverscmp(3) on the strings
(*a)->d_name and (*b)->d_name.
scandirat()
The scandirat() function operates in exactly the same way as
scandir(), except for the differences described here.
If dirp is relative, then it is interpreted relative to the
directory referred to by the file descriptor dirfd (rather than
relative to the current working directory of the calling process,
as is done by scandir() for a relative pathname).
If dirp is relative and dirfd is the special value AT_FDCWD, then
dirp is interpreted relative to the current working directory of
the calling process (like scandir()).
If dirp is absolute, then dirfd is ignored.
See openat(2) for an explanation of the need for scandirat().
The scandir() function returns the number of directory entries
selected. On error, -1 is returned, with errno set to indicate
the error.
The alphasort() and versionsort() functions return an integer less
than, equal to, or greater than zero if the first argument is
considered to be respectively less than, equal to, or greater than
the second.
EBADF (scandirat()) dirp is relative but dirfd is neither
AT_FDCWD nor a valid file descriptor.
ENOENT The path in dirp does not exist.
ENOMEM Insufficient memory to complete the operation.
ENOTDIR
The path in dirp is not a directory.
ENOTDIR
(scandirat()) dirp is relative and dirfd is a file
descriptor referring to a file other than a directory.
For an explanation of the terms used in this section, see
attributes(7).
┌───────────────────────────────┬───────────────┬────────────────┐
│ Interface │ Attribute │ Value │
├───────────────────────────────┼───────────────┼────────────────┤
│ scandir(), scandirat() │ Thread safety │ MT-Safe │
├───────────────────────────────┼───────────────┼────────────────┤
│ alphasort(), versionsort() │ Thread safety │ MT-Safe locale │
└───────────────────────────────┴───────────────┴────────────────┘
alphasort()
scandir()
POSIX.1-2008.
versionsort()
scandirat()
GNU.
alphasort()
scandir()
4.3BSD, POSIX.1-2008.
versionsort()
glibc 2.1.
scandirat()
glibc 2.15.
Since glibc 2.1, alphasort() calls strcoll(3); earlier it used
strcmp(3).
Before glibc 2.10, the two arguments of alphasort() and
versionsort() were typed as const void *. When alphasort() was
standardized in POSIX.1-2008, the argument type was specified as
the type-safe const struct dirent **, and glibc 2.10 changed the
definition of alphasort() (and the nonstandard versionsort()) to
match the standard.
The program below prints a list of the files in the current
directory in reverse order.
Program source
#define _DEFAULT_SOURCE
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
int
main(void)
{
struct dirent **namelist;
int n;
n = scandir(".", &namelist, NULL, alphasort);
if (n == -1) {
perror("scandir");
exit(EXIT_FAILURE);
}
while (n--) {
printf("%s\n", namelist[n]->d_name);
free(namelist[n]);
}
free(namelist);
exit(EXIT_SUCCESS);
}
closedir(3), fnmatch(3), opendir(3), readdir(3), rewinddir(3),
seekdir(3), strcmp(3), strcoll(3), strverscmp(3), telldir(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-05-17 scandir(3)
Pages that refer to this page: open(2), closedir(3), dirfd(3), fnmatch(3), opendir(3), qsort(3), readdir(3), rewinddir(3), seekdir(3), telldir(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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