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



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);

   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 non-zero 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 or -1 if an
       error occurs.

       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
       ENOMEM Insufficient memory to complete the operation.

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, 0, 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),  seekdir(3),  str-
       cmp(3), strcoll(3), strverscmp(3), telldir(3)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of
       the project, and information about reporting bugs, can be found at  http://www.ker-
       nel.org/doc/man-pages/.



GNU                               2009-02-10                        SCANDIR(3)

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