LDAP_SORT(3LDAP) LDAP Library Functions LDAP_SORT(3LDAP)


NAME


ldap_sort, ldap_sort_entries, ldap_sort_values, ldap_sort_strcasecmp -
LDAP entry sorting functions

SYNOPSIS


cc[ flag... ] file... -lldap[ library... ]
#include <lber.h>
#include <ldap.h>

ldap_sort_entries(LDAP *ld, LDAPMessage **chain, char *attr,
int (*cmp)());


ldap_sort_values(LDAP *ld, char **vals, int (*cmp)());


ldap_sort_strcasecmp(char *a, char *b);


DESCRIPTION


These functions are used to sort lists of entries and values retrieved
from an LDAP server. 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 ld, the LDAP structure,
which is only used for error reporting, chain, the list of entries as
returned by ldap_search_s(3LDAP) or ldap_result(3LDAP). attr is the
attribute to use as a key in the sort or NULL to sort by DN, and cmp is
the comparison function to use when comparing values (or individual DN
components if sorting by DN). In this case, cmp should be a function
taking two single values of the attr 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 qsort(3C), which is
called to do the actual sorting.


ldap_sort_values() is used to sort an array of values from an entry, as
returned by ldap_get_values(3LDAP). It takes the LDAP connection
structure ld, the array of values to sort vals, and cmp, the
comparison function to use during the sort. Note that cmp will be passed
a pointer to each element in the vals array, so if you pass the normal
char ** for this parameter, cmp should take two char **'s as arguments
(that is, you cannot pass strcasecmp or its friends for cmp). You can,
however, pass the function ldap_sort_strcasecmp() for this purpose.


For example:

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" );


ATTRIBUTES


See attributes(5) for a description of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|Interface Stability | Evolving |
+--------------------+-----------------+

SEE ALSO


ldap(3LDAP), ldap_search(3LDAP), ldap_result(3LDAP), qsort(3C),
attributes(5)

NOTES


The ldap_sort_entries() function applies the comparison function to each
value of the attribute in the array as returned by a call to
ldap_get_values(3LDAP), 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
functions may allocate memory which must be freed by the calling
application.


January 27, 2002 LDAP_SORT(3LDAP)