scandirat(3) — Linux manual page


SCANDIR(3)                Linux Programmer's Manual               SCANDIR(3)

NAME         top

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

SYNOPSIS         top

       #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 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 *dirp, struct dirent ***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 versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

       versionsort(): _GNU_SOURCE

       scandirat(): _GNU_SOURCE

DESCRIPTION         top

       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

       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.

       The scandirat() function operates in exactly the same way as
       scandir(), except for the differences described here.

       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().

RETURN VALUE         top

       The scandir() function returns the number of directory entries
       selected.  On error, -1 is returned, with errno set to indicate the
       cause of 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.

ERRORS         top

       ENOENT The path in dirp does not exist.

       ENOMEM Insufficient memory to complete the operation.

              The path in dirp is not a directory.

       The following additional errors can occur for scandirat():

       EBADF  dirfd is not a valid file descriptor.

              dirp is a relative path and dirfd is a file descriptor
              referring to a file other than a directory.

VERSIONS         top

       versionsort() was added to glibc in version 2.1.

       scandirat() was added to glibc in version 2.15.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface                  Attribute     Value          │
       │scandir(), scandirat()     │ Thread safety │ MT-Safe        │
       │alphasort(), versionsort() │ Thread safety │ MT-Safe locale │

CONFORMING TO         top

       alphasort(), scandir(): 4.3BSD, POSIX.1-2008.

       versionsort() and scandirat() are GNU extensions.

NOTES         top

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

       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

EXAMPLES         top

       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>

           struct dirent **namelist;
           int n;

           n = scandir(".", &namelist, NULL, alphasort);
           if (n == -1) {

           while (n--) {
               printf("%s\n", namelist[n]->d_name);


SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

GNU                              2020-06-09                       SCANDIR(3)

Pages that refer to this page: creat(2)open(2)openat(2)