alphasort

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 *dir, struct dirent ***namelist,
              int(*select)(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);

DESCRIPTION
       The scandir() function scans the directory  dir,  calling  select()  on
       each  directory entry.  Entries for which select() returns non-zero are
       stored in strings allocated via malloc(), sorted using qsort() with the
       comparison  function compar(), and collected in array namelist which is
       allocated via malloc().  If select 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.

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 consid-
       ered to be respectively less than, equal to, or greater than  the  sec-
       ond.

ERRORS
       ENOMEM Insufficient memory to complete the operation.

CONFORMING TO
       None  of  these  functions  is  in  POSIX.  The functions scandir() and
       alphasort() are from BSD 4.3, 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
       /* print files in current directory in reverse order */
       #include <dirent.h>
       main(){
           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)



GNU                               2001-12-26                        SCANDIR(3)