The Lightweight Directory Access Protocol (LDAP) (RFC 4510) provides
access to X.500 directory services. These services may be stand-alone
or part of a distributed directory service. This client API supports
LDAP over TCP (RFC 4511), LDAP over TLS/SSL, and LDAP over IPC (UNIX
domain sockets). This API supports SASL (RFC 4513) and Start TLS
(RFC 4513) as well as a number of protocol extensions. This API is
loosely based upon IETF/LDAPEXT C LDAP API draft specification, a (orphaned)
work in progress.
The OpenLDAP Software package includes a stand-alone server in
various LDAP clients, and an LDAP client library used to provide
programmatic access to the LDAP protocol. This man page gives an
overview of the LDAP library routines.
Both synchronous and asynchronous APIs are provided. Also included are
various routines to parse the results returned from these routines.
These routines are found in the -lldap library.
The basic interaction is as follows. A session handle is
and set the protocol version to 3 by calling
The underlying session is established first operation is
issued. This would generally be a Start TLS or Bind operation,
or a Search operation to read attributes of the Root DSE.
A Start TLS operation is performed by calling
A LDAP bind operation is performed by calling
or one of its friends.
A Search operation is performed by calling ldap_search_ext_s(3)
or one of its friends.
This library supports version 3 of the Lightweight Directory Access
Protocol (LDAPv3) as defined in RFC 4510. It also supports a variant
of version 2 of LDAP as defined by U-Mich LDAP and, to some degree,
RFC 1777. Version 2 (all variants) are considered obsolete.
Version 3 should be used instead.
For backwards compatibility reasons, the library defaults to version 2.
Hence, all new applications (and all actively maintained applications)
to select version 3. The library manual pages assume version 3
has been selected.
INPUT and OUTPUT PARAMETERS
All character string input/output is expected to be/is UTF-8
encoded Unicode (version 3.2).
Distinguished names (DN) (and relative distinguished names (RDN) to
be passed to the LDAP routines should conform to RFC 4514 UTF-8
Search filters to be passed to the search routines are to be
constructed by hand and should conform to RFC 4515 UTF-8
LDAP URLs to be passed to routines are expected to conform
to RFC 4516 format. The
routines can be used to work with LDAP URLs.
LDAP controls to be passed to routines can be manipulated using the
Also provided are various utility routines. The
routines are used to sort the entries and values returned via
the ldap search routines.
A number of interfaces are now considered deprecated. For instance,
ldap_add(3) is deprecated in favor of ldap_add_ext(3).
Deprecated interfaces generally remain in the library. The macro
LDAP_DEPRECATED can be defined to a non-zero value
(e.g., -DLDAP_DEPRECATED=1) when compiling program designed to use
deprecated interfaces. It is recommended that developers writing new
programs, or updating old programs, avoid use of deprecated interfaces.
Over time, it is expected that documentation (and, eventually, support) for
deprecated interfaces to be eliminated.
Also included in the distribution is a set of lightweight Basic
Encoding Rules routines. These routines are used by the LDAP library
routines to encode and decode LDAP protocol elements using the
(slightly simplified) Basic Encoding Rules defined by LDAP. They are
not normally used directly by an LDAP application program except
in the handling of controls and extended operations. The
routines provide a printf and scanf-like interface, as well as
lower-level access. These routines are discussed in