scandir

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



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

SYNOPSIS
       #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

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.

   scandirat()
       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
       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
       ENOENT The path in dirp does not exist.

       ENOMEM Insufficient memory to complete the operation.

       ENOTDIR
              The path in dirp is not a directory.

       The following additional errors can occur for scandirat():

       EBADF  dirfd is not a valid file descriptor.

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

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

       scandirat() was added to glibc in version 2.15.

ATTRIBUTES
       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 │
       └───────────────────────────────────────┴───────────────┴────────────────┘

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

       versionsort() and scandirat() are GNU extensions.

NOTES
       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.

EXAMPLES
       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);
       }

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

COLOPHON
       This page is part of release 5.11 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
       https://www.kernel.org/doc/man-pages/.



GNU                                2021-03-22                         SCANDIR(3)