.TH LDAP_SORT 3 "RELEASEDATE" "OpenLDAP LDVERSION"
.\" $OpenLDAP: pkg/ldap/doc/man/man3/ldap_sort.3,v 1.13.2.4 2007/01/02 21:43:45 kurt Exp $
.\" Copyright 1998-2007 The OpenLDAP Foundation All Rights Reserved.
.\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
.SH NAME
ldap_sort_entries, ldap_sort_values, ldap_sort_strcasecmp \- LDAP sorting routines
.SH LIBRARY
OpenLDAP LDAP (libldap, -lldap)
.SH SYNOPSIS
.nf
.ft B
#include <ldap.h>
.LP
.ft B
ldap_sort_entries(ld, chain, attr, cmp)
.ft
LDAP *ld;
LDAPMessage **chain;
char *attr;
int (*cmp)();
.LP
.ft B
ldap_sort_values(ld, vals, cmp)
.ft
LDAP *ld;
char **vals;
int (*cmp)();
.LP
.ft B
ldap_sort_strcasecmp(a, b)
.ft
char *a;
char *b;
.SH DESCRIPTION
These routines are used to sort lists of entries and values retrieved
from an LDAP server.
.B ldap_sort_entries()
is used to sort a chain
of entries retrieved from an LDAP search call either by DN or by some
arbitrary attribute in the entries.  It takes \fIld\fP, the LDAP
structure, which is only used for error reporting, \fIchain\fP, the
list of entries as returned by
.BR ldap_search_s (3)
or
.BR ldap_result (3).
\fIattr\fP is the attribute to use as a key in the sort
or NULL to sort by DN, and \fIcmp\fP is the comparison function to use
when comparing values (or individual DN components if sorting by DN).
In this case, \fIcmp\fP should be a function taking two single values
of the \fIattr\fP to sort by, and returning a value less than zero,
equal to zero, or greater than zero, depending on whether the first
argument is less than, equal to, or greater than the second argument.
The convention is the same as used by
.BR qsort (3),
which is called to do the actual sorting.
.LP
.B ldap_sort_values()
is used to sort an array of values from an entry,
as returned by
.BR ldap_get_values (3).
It takes the LDAP connection
structure \fIld\fP, the array of values
to sort \fIvals\fP, and \fIcmp\fP, the comparison
function to use during the sort.
Note that \fIcmp\fP will be passed a pointer to each element in the
\fIvals\fP array, so if you pass the normal char ** for this parameter,
\fIcmp\fP should take two char **'s as arguments (i.e., you cannot
pass \fIstrcasecmp\fP or its friends for \fIcmp\fP).  You can, however,
pass the function
.B ldap_sort_strcasecmp()
for this purpose.
.LP
For example:
.LP
.nf
.ft tt
	LDAP *ld;
	LDAPMessage *res;

	/*
	 * ... call to ldap_search_s(), fill in res,
	 * retrieve sn attr ...
	 */

	/* now sort the entries on surname attribute */
	if ( ldap_sort_entries( ld, &res, "sn",
			ldap_sort_strcasecmp ) != 0 )
		ldap_perror( ld, "ldap_sort_entries" );
.ft
.fi
.SH NOTES
.LP
The
.B ldap_sort_entries()
routine applies the comparison function to
each value of the attribute in the array as returned by a call to
.BR ldap_get_values (3),
until a mismatch is found.
This works fine for single-valued attributes, but
may produce unexpected results for multi-valued attributes.
When sorting by DN, the comparison function is
applied to an exploded version of the DN, without types.
The return values for all of these functions are declared in the
<ldap.h> header file.  Some routines may dynamically allocate memory.
Callers are responsible for freeing such memory using the supplied
deallocation routines.
.SH SEE ALSO
.BR ldap (3),
.BR ldap_search (3),
.BR ldap_result (3),
.BR qsort (3)
.SH ACKNOWLEDGEMENTS
.B OpenLDAP
is developed and maintained by The OpenLDAP Project (http://www.openldap.org/).
.B OpenLDAP
is derived from University of Michigan LDAP 3.3 Release.