scandir(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 *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

       scandir(), alphasort():
           /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
               || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_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 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.

       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

       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 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

       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.

              The path in dirp is not a directory.

              (scandirat()) dirp is a relative pathname and dirfd is a
              file descriptor referring to a file other than a

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 standard.

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 5.13 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                            2021-08-27                     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)strverscmp(3)telldir(3)