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 *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
       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 compari-
       son function compar().  The former sorts directory entries  using  str-
       coll(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 rela-
       tive 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
       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 consid-
       ered to be respectively less than, equal to, or greater than  the  sec-
       ond.

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 str-
       cmp(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.

EXAMPLE
       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 4.10 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				  2017-03-13			    SCANDIR(3)