Content-type: text/html Man page of cfg_subsys_query

cfg_subsys_query

Section: C Library Functions (3)
Index Return to Main Contents
 

NAME

cfg_subsys_query - Determine the value of selected subsystem attributes  

LIBRARY

Configuration Management Library (libcfg.a)  

SYNOPSIS

#include <cfg.h> cfg_status_t cfg_subsys_query(
        cfg_handle_t *handle,
        caddr_t subsys,
        cfg_attr_t *attributes,
        int nattributes);  

PARAMETERS

Structure identifying the means of communication between your application and the configuration management server. For local requests, pass NULL in this parameter. For remote requests, pass the value returned from the cfg_connect() routine. Specifies the name of the subsystem for which you are getting attribute values. On input, names the attributes for which you are requesting a value.

On return, contains information about the named attributes. The information includes the data type of the attribute, the list of operations supported by that attribute, the attribute-specific status of the query operation, the minimum and maximum allowed values for the attribute, and the current value of the attribute. For binary data items, the information includes the size of the attribute's current value. An integer value specifying the number of attributes for which you are requesting information.
 

DESCRIPTION

Use the cfg_subsys_query() routine to get information about a list of subsystem attributes. You can get information about one or more attributes.

When your application calls the cfg_subsys_query() routine, it passes the subsystem name and a list of attribute names to the system. The system reads this information and finds and collects the information about the named attributes. The system then returns the attribute information to your application.

The information returned from the cfg_subsys_query() routine is passed in a structure of type cfg_attr_t. If your application requests information about more than one attribute, an array of structures is returned. For information about this structure, see libcfg(3).

The following list describes the information returned to your application when it calls the cfg_subsys_query() routine: Attributes can be integer, string, or binary data. As defined in <sys/sysconfig.h>, the integer data types can be CFG_ATTR_INTTYPE (int), CFG_ATTR_UINTTYPE (uint), CFG_ATTR_LONGTYPE (long), or CFG_ATTR_ULONGTYPE (ulong). The string data type is a character string type named CFG_ATTR_STRTYPE and the binary data type is CFG_ATTR_BINTYPE. The definition of each attribute in the subsystem code determines what operations you can perform on the attribute. The possible operation code are CFG_OP_QUERY (you can request information about the attribute), CFG_OP_CONFIGURE (you can set the attribute value when the subsystem is initially configured), and CFG_OP_RECONFIGURE (you can modify the value of the attribute). During a query request, the system assigns a status to each attribute. The following table describes the status values that your application might receive from the cfg_subsys_query() routine:

Status CodeMeaning

CFG_ATTR_SUCCESSSuccessful operation
CFG_ATTR_EEXISTSNo attribute by that name exists
CFG_ATTR_EOPAttribute does not support the query operation
CFG_ATTR_ESUBSYS Subsystem failure (code within the subsystem returned an error)
CFG_ATTR_EINDEX The index for an indexed attribute is out of range
CFG_ATTR_EMEM Unable to allocate memory to return the attribute value

The value of each attribute is returned in a structure. In addition to the attribute value, this structure returns the minimum and maximum value for the attribute, the disposal routine, if any, to be called once the attribute value is returned, and for binary attributes, the length of the current value of the attribute. (The disposal routine is used to free temporary kernel memory occupied by string and binary data.)  

EXAMPLES

The following example illustrates the use of the cfg_subsys_query() library routine: cfg_attr_t attributes[2]; cfg_status_t retval; cfg_handle_t handle; int i;

/*****************************************************/ /* Initialize attribute names for the query */

strcpy (attributes[0].name, "nmounts"); strcpy (attributes[1].name, "mountpoint");

/***************************************************/ /* Call the cfg_subsys_query() routine */

retval = cfg_subsys_query(&handle, "lvm", attributes, 2);

if (retval != CFG_SUCCESS)
    print_error (retval);

else {
     /*  Use data returned from the query          */


     for (i=0; i<2; i++) {
         printf ("%s", attributes[i].name);
         if (attributes[i].status != CFG_ATTR_SUCCESS) {
             switch (attributes[i].status){
             case CFG_ATTR_EEXISTS:
               printf("unknown attribute\n");
               break;
             case CFG_ATTR_EOP:
               printf("attribute does not allow this operation\n");
               break;
             .
             .
             .
             default:
               printf("unknown error\n");
               break;
             }
             continue;
         }


   /*     Display attribute value to application user   */


         switch (attributes[i].type){
         case CFG_ATTR_INTTYPE:
           printf ("%d\n", (int) attributes[i].attr.num.val);
           break;
         .
         .
         .
         case CFG_ATTR_STRTYPE:
           printf ("%s\n", (int) attributes[i].attr.str.val);
           free(attributes[i].attr.str.val);
           break;


         case CFG_ATTR_BINTYPE:
           printf ("%d bytes of binary data received\n",
                    (int) attributes[i].attr.bin.val_size);
           free(attributes[i].attr.str.val);
           break;
         }
       }
    }

In this example, the application requests information about two attributes, nmounts and mountpoint. When the cfg_subsys_query() routine returns information about those attributes, the application tests the return status of the routine. The application reports any errors returned. If cfg_subsys_query() routine returns CFG_SUCCESS, the status for each attribute is tested and any errors are reported. The application displays to the user the value of attributes that return CFG_ATTR_SUCCESS. Note that the configuration management library allocates memory to hold the attribute value of each string and binary-type attribute being queried. Therefore, after using an attribute value, applications must free the allocated memory space to avoid a memory leak.  

RETURN VALUES

Upon successful completion, cfg_subsys_query() returns CFG_SUCCESS. Other return values indicate that an error has occurred. For information about handling return values from routines in the configuration management library, see libcfg(3).  

RELATED INFORMATION

Commands: cfgmgr(8), sysconfig(8)

Routines: cfg_connect(3), cfg_subsys_query_all(3), libcfg(3) delim off


 

Index

NAME
LIBRARY
SYNOPSIS
PARAMETERS
DESCRIPTION
EXAMPLES
RETURN VALUES
RELATED INFORMATION

This document was created by man2html, using the manual pages.
Time: 02:41:26 GMT, October 02, 2010