cfg_subsys_query(3) Library Functions Manual cfg_subsys_query(3)
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 sub-
system 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).
To query an individual array element, on input the index field of the cfg_attr_t structure must be set to the index value of the array ele-
ment.
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 Code Meaning
---------------------------------------------------------------------
CFG_ATTR_SUCCESS Successful operation
CFG_ATTR_EEXISTS No attribute by that name exists
CFG_ATTR_EOP Attribute 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 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, "bufcache"); strcpy (attributes[1].name, "max-vnodes");
/***************************************************/ /* Call the cfg_subsys_query() routine */
retval = cfg_subsys_query(&handle, "vfs", 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
");
break;
case CFG_ATTR_EOP:
printf("attribute does not allow this operation
");
break;
.
.
.
default:
printf("unknown error
");
break;
}
continue;
}
/* Display attribute value to application user */
switch (attributes[i].type){
case CFG_ATTR_INTTYPE:
printf ("%d
", (int) attributes[i].attr.num.val);
break;
.
.
.
case CFG_ATTR_STRTYPE:
printf ("%s
", (int) attributes[i].attr.str.val);
free(attributes[i].attr.str.val);
break;
case CFG_ATTR_BINTYPE:
printf ("%d bytes of binary data received
",
(int) attributes[i].attr.bin.val_size);
free(attributes[i].attr.str.val);
break;
}
}
}
In this example, the application requests information about two attributes, bufcache and max-vnodes. 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.
RETURN VALUES
Upon successful completion, cfg_subsys_query() returns CFG_SUCCESS. Other return values indicate that an error has occurred. For informa-
tion 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
cfg_subsys_query(3)