GENDERS_QUERY(3)

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)