SCANDIR(3)

NAME
scandir, alphasort, versionsort - scan a directory for matching entries

SYNOPSIS
#include <dirent.h>

int scandir(const char *dirp, struct dirent ***namelist,
    int (*filter)(const struct dirent *),
    int (*compar)(const struct dirent **, const struct dirent **));

int alphasort(const void *a, const void *b);

int versionsort(const void *a, const void *b);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

scandir(), alphasort(): _BSD_SOURCE || _SVID_SOURCE
versionsort(): _GNU_SOURCE

DESCRIPTION
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.

RETURN VALUE
The scandir() function returns the number of directory entries selected or -1 if an error occurs.

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.

ERRORS

ENOENT
    The path in dirp does not exist.

ENOMEM
    Insufficient memory to complete the operation.

ENOTDIR
    The path in dirp is not a directory.

VERSIONS
versionsort() was added to glibc in version 2.1.

CONFORMING TO
alphasort() and scandir() are specified in POSIX.1-2008, and are widely available. versionsort() is a GNU extension.

The functions scandir() and alphasort() are from 4.3BSD, and have been available under Linux since libc4. Libc4 and libc5 use the more precise prototype

    int alphasort(const struct dirent ** a,
                  const struct dirent **b);

but glibc 2.0 returns to the imprecise BSD prototype.

The function versionsort() is a GNU extension, available since glibc 2.1.

Since glibc 2.1, alphasort() calls strcoll(3); earlier it used strcmp(3).

EXAMPLE
#define _SVID_SOURCE
/* print files in current directory in reverse order */
#include <dirent.h>

int
main(void)
{
    struct dirent **namelist;
    int n;

    n = scandir(".", &namelist, NULL, alphasort);
    if (n < 0)
        perror("scandir");
    else {
        while (n--) {
            printf("%s\n", namelist[n]->d_name);
            free(namelist[n]);
        }
        free(namelist);
    }
}

SEE ALSO
closedir(3), fnmatch(3), opendir(3), readdir(3), rewinddir(3), scandirat(3), seekdir(3), strcmp(3), strcoll(3), strverscmp(3), telldir(3)

COLOPHON
This page is part of release 3.50 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.