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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);
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(), sorted using qsort() with the
comparison function compar(), and collected in array namelist which is
allocated via malloc(). 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. LSB has deprecated the library
call alphasort() and never contained scandir().
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
/* 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)