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NAME

       genders_query - query genders database for a set of nodes

SYNOPSIS

       #include <genders.h>

       int  genders_query(genders_t handle, char *nodes[], int len, const char
       *query);

DESCRIPTION

       genders_query() queries the genders database for a set of  nodes  based
       on  the  union,  intersection,  difference,  or  complement  of genders
       attributes and values.  The query for a set of nodes  is  passed  as  a
       string  through  the  query  parameter.   The  set  operation  union is
       represented by two pipe symbols (’||’), intersection by  two  ampersand
       symbols  (’&&’), difference by two minus symbols (’--’), and complement
       by a  tilde  (’~’).   Set  operations  are  performed  left  to  right.
       Parentheses  may  be used to change the order of operations.  A list of
       query examples are listed below.  A NULL query retrieves all nodes from
       the genders database.

       The  nodes  from  the query are stored in the list pointed to by nodes.
       len indicates the number of nodes that can be stored in the list.

       To avoid passing in a list that is not large enough to  store  all  the
       nodes,  genders_getnumnodes(3)  should be used to determine the minimum
       number   of   elements    nodes    should    be    able    to    store.
       genders_nodelist_create(3)  could  be  used  to  create  a list that is
       guaranteed to be large enough to store all of the nodes.

EXAMPLES

       The  following  are   example   queries   that   can   be   passed   to
       genders_query().

       Determine the set of nodes with the mgmt or login attribute:
               "mgmt||login"

       Determine the set of nodes that are not login nodes:
               "all--login"

       Determine the set of nodes that both login nodes and ntp servers:
               "login&&ntpserv"

       Determine the set of nodes that are not mgmt or login nodes:
               "~(mgmt||login)"

RETURN VALUES

       On success, the number of nodes stored in nodes is returned.  On error,
       -1 is returned, and an error code is returned  in  handle.   The  error
       code  can be retrieved via genders_errnum(3) , and a description of the
       error code can be retrieved via genders_strerror(3).  Error  codes  are
       defined in genders.h.

ERRORS

       GENDERS_ERR_NULLHANDLE
              The  handle  parameter  is  NULL.   The  genders  handle must be
              created with genders_handle_create(3).

       GENDERS_ERR_NOTLOADED
              genders_load_data(3) has not been called to load genders data.

       GENDERS_ERR_OVERFLOW
              The list pointed to by nodes is not large enough  to  store  all
              the nodes.

       GENDERS_ERR_PARAMETERS
              An incorrect parameter has been passed in.

       GENDERS_ERR_SYNTAX
              There is a syntax error in the query.

       GENDERS_ERR_OUTMEM
              malloc(3) has failed internally, system is out of memory.

       GENDERS_ERR_NULLPTR
              A null pointer has been found in the list passed in.

       GENDERS_ERR_MAGIC
              handle  has an incorrect magic number.  handle does not point to
              a   genders   handle   or   handle   has   been   destroyed   by
              genders_handle_destroy(3).

       GENDERS_ERR_INTERNAL
              An internal system error has occurred.

FILES

       /usr/include/genders.h

SEE ALSO

       libgenders(3),      genders_handle_create(3),     genders_load_data(3),
       genders_getnumnodes(3), genders_nodelist_create(3),  genders_errnum(3),
       genders_strerror(3)