Linux manual pages Section 3: Subroutines  

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);
 
[Note] Note
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. 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

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 3.52 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/.


  Copyright (C) 1993 David Metcalfe (davidprism.demon.co.uk)

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References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages
Modified Sat Jul 24 18:26:16 1993 by Rik Faith (faithcs.unc.edu)
Modified Thu Apr 11 17:11:33 1996 by Andries Brouwer (aebcwi.nl):
    Corrected type of compar routines, as suggested by
    Miguel Barreiro (enanoavalon.yaix.es).  Added example.
Modified Sun Sep 24 20:15:46 2000 by aeb, following Petter Reinholdtsen.
Modified 2001-12-26 by aeb, following Joey. Added versionsort.