scandir, alphasort, versionsort — scan a directory for matching entries
#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) ; |
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
.
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.
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).
/* 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); } }
closedir(3), fnmatch(3), opendir(3), readdir(3), rewinddir(3), seekdir(3), strcmp(3), strcoll(3), strverscmp(3), telldir(3)
|