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 nonzero are stored in strings allocated via malloc(3), sorted using qsort(3) with the  comparison  function  com-
       par(), 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),  strcmp(3),  strcoll(3),   strverscmp(3),
       telldir(3)

COLOPHON
       This  page  is  part of release 3.25 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/.



GNU                                                        2009-02-10                                                 SCANDIR(3)