#include <dirent.h>
int scandir(const char *restrict dirp,
struct dirent ***restrict namelist,
int (*filter)(const struct dirent *),
int (*compar)(const struct dirent **,
const struct dirent **));
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,
int (*filter)(const struct dirent *),
int (*compar)(const struct dirent **,
const struct dirent **));
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 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.
If the pathname given in 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 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.
The following additional errors can occur for scandirat():
scandirat() was added to glibc in version 2.15.
| Interface | Attribute | Value |
| scandir(), scandirat() | Thread safety | MT-Safe |
| alphasort(), versionsort() | Thread safety | MT-Safe locale |
versionsort() and scandirat() are GNU extensions.
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.
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);