NAME
scandir,
scandirat, alphasort
— scan a directory
SYNOPSIS
#include
<sys/types.h>
#include <dirent.h>
int
scandir(const char *dirname,
struct dirent ***namelist, int
(*select)(const struct dirent *), int (*compar)(const
struct dirent **, const struct dirent **));
int
scandirat(int dirfd,
const char *dirname, struct dirent
***namelist, int (*select)(const struct dirent
*), int (*compar)(const struct dirent **, const struct
dirent **));
int
alphasort(const
struct dirent **d1, const
struct dirent **d2);
DESCRIPTION
The
scandir()
function reads the directory dirname and builds an
array of pointers to directory entries using
malloc(3).
It returns the number of entries in the array. A pointer to the array of
directory entries is stored in the location referenced by
namelist.
The select parameter is a
pointer to a user-supplied subroutine which is called by
scandir()
to select which entries are to be included in the array. The select routine
is passed a pointer to a directory entry and should return a non-zero value
if the directory entry is to be included in the array. If
select is NULL, then all
directory entries will be included.
The compar parameter is a pointer to a
user-supplied subroutine which is passed to
qsort(3) to
sort the completed array. If this pointer is NULL,
the array is not sorted.
The
alphasort()
function is a routine which can be used for the compar
parameter to sort the array alphabetically.
The memory allocated for the array can be deallocated with free(3), by freeing each pointer in the array and then the array itself.
The
scandirat()
function is similar to scandir(), but takes an
additional dirfd argument. If
dirname is relative, dirfd must
be a valid file descriptor referencing a directory, in which case the
dirname lookup is performed relative to the directory
referenced by dirfd. If dirfd
has the special value AT_FDCWD, then the current
process directory is used as the base for relative lookups. See
openat(2)
for additional details.
DIAGNOSTICS
Returns -1 if the directory cannot be opened for reading or if malloc(3) cannot allocate enough memory to hold all the data structures.
SEE ALSO
STANDARDS
The scandir() and
alphasort() functions conform to
IEEE Std 1003.1-2008 (“POSIX.1”).
HISTORY
The scandir() and
alphasort() functions appeared in
4.2BSD.
The argument types for alphasort() and for
the compar argument to
scandir() were originally void
*, then changed to const void *, and then
finally changed by IEEE Std 1003.1-2008
(“POSIX.1”) to their current form of
const struct dirent **. Similarly, the
select() argument to
scandir() was originally struct
dirent * until it was changed to its current form of
const struct dirent *.