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(7) for a description of the following attributes:


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

SEE ALSO

qsort(3C), ldap(3LDAP), ldap_result(3LDAP), ldap_search(3LDAP),
attributes(7)

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)