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NAME

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

SYNOPSIS

       #include <dirent.h>

       int scandir(const char *dir, 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  dir,  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.

CONFORMING TO

       None of  these  functions  is  in  POSIX.1-2001,  but  alphasort()  and
       scandir() are under consideration for a future revision to POSIX.1.

       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), strcmp(3), strcoll(3), strverscmp(3), telldir(3)

COLOPHON

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       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.