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.\"     @(#)scandir.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/gen/scandir.3,v 1.9 2007/01/09 00:27:55 imp Exp $
.\"
.Dd May 20, 2008
.Dt SCANDIR 3
.Os
.Sh NAME
.Nm scandir ,
#ifdef UNIFDEF_BLOCKS
.Nm scandir_b ,
#endif
.Nm alphasort
.Nd scan a directory
.Sh SYNOPSIS
.In sys/types.h
.In dirent.h
.Ft int
.Fn scandir "const char *dirname" "struct dirent ***namelist" "int \\*(lp*select\\*(rp\\*(lpstruct dirent *\\*(rp" "int \\*(lp*compar\\*(rp\\*(lpconst void *, const void *\\*(rp"
.Ft int
.Fn alphasort "const void *d1" "const void *d2"
#ifdef UNIFDEF_BLOCKS
.Ft int
.Fn scandir_b "const char *dirname" "struct dirent ***namelist" "int \\*(lp^select\\*(rp\\*(lpstruct dirent *\\*(rp" "int \\*(lp^compar\\*(rp\\*(lpconst void *, const void *\\*(rp"
#endif
.Sh DESCRIPTION
The
.Fn scandir
function
reads the directory
.Fa dirname
and builds an array of pointers to directory
entries using
.Xr 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
.Fa namelist .
.Pp
The
.Fa select
argument is a pointer to a user supplied subroutine which is called by
.Fn 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
.Fa select
is null, then all the directory entries will be included.
.Pp
The
.Fa compar
argument is a pointer to a user supplied subroutine which is passed to
.Xr qsort 3
to sort the completed array.
If this pointer is null, the array is not sorted.
Note that from within the
.Fa compar
subroutine, the two arguments are of type
.Ft const struct dirent ** ,
so that a double-dereference is needed to access the fields in the
.Ft dirent
structure.
.Pp
The
.Fn alphasort
function
is a routine which can be used for the
.Fa compar
argument to sort the array alphabetically.
.Pp
The memory allocated for the array can be deallocated with
.Xr free 3 ,
by freeing each pointer in the array and then the array itself.
#ifdef UNIFDEF_BLOCKS
.Pp
The
.Fn scandir_b
function works the same way as the
.Fn scandir
function, except that
.Fa select
and
.Fa compar
are blocks instead of subroutines.
#endif
.Sh DIAGNOSTICS
Returns \-1 if the directory cannot be opened for reading or if
.Xr malloc 3
cannot allocate enough memory to hold all the data structures.
.Sh SEE ALSO
.Xr directory 3 ,
.Xr malloc 3 ,
.Xr qsort 3 ,
.Xr dir 5
.Sh HISTORY
The
.Fn scandir
and
.Fn alphasort
functions appeared in
.Bx 4.2 .
#ifdef UNIFDEF_BLOCKS
The
.Fn scandir_b
function appeared in Mac OS X 10.6.
#endif