Manpage of MIB_API


Section: C Library Functions (3)
Updated: 07 Aug 2000
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init_mib, add_mibdir, init_mib_internals, add_module_replacement, read_module, read_mib, read_all_mibs, read_objid, read_module_node, get_module_node snmp_set_mib_warnings, snmp_set_save_descriptions, shutdown_mib, print_mib, print_variable, print_value, print_objid, print_description - mib_api functions  


#include <stdio.h>
#include <sys/types.h>
#include <ucd-snmp/asn1.h>
#include <ucd-snmp/mib.h>
#include <ucd-snmp/parse.h>

void init_mib( void )
int add_mibdir( char *dirname )
int add_module_replacement( char *old_module, char *new_module, char *tag, int len )
void init_mib_internals( void )
struct tree *read_module( char *name )
struct tree *read_mib( char *filename )
struct tree *read_all_mibs( void )

void shutdown_mib( void )

void print_mib( FILE *fp)

int read_objid( char *input, oid *output, size_t *out_len)
int get_module_node( char *name, char *module, oid *objid, size_t *objidlen )

void print_variable( oid *objid, size_t objidlen, struct variable_list *variable)
void print_value( oid *objid, size_t objidlen, struct variable_list *variable)
void print_objid( oid *objid, size_t objidlen);
void print_description( oid *objid, size_t objidlen, int width);
void snmp_set_mib_warnings( int );
void snmp_set_save_descriptions( int );



The functions dealing with MIB modules fall into four groups. Those dealing with initialisation, those that read in and parse MIB files, those that search the MIB tree, and various output routines.

init_mib is a convenience function that handles all calls to add_mibdir, read_module and read_mib for standard applications. It should be called before any other routine that manipulates or accesses the MIB tree. This routine sets up various internal structures, as well as reading in the default MIB modules, as detailed below.

add_mibdir is used to define the range of directory locations which are searched for files containing MIB modules (one module per file). By default, this will be set to the directory DATADIR/mibs but this can be overridden by setting the environment variable MIBDIRS to a (colon-separated) list of directories to search. Note that this does not actually load the MIB modules located in that directory, but is an initialisation step to make them available. This function returns a count of files found in the directory, or a -1 if there is an error.

init_mib_internals sets up the internal structures, preparatory to reading in MIB modules. It should be called after all calls to add_mibdir, and before and calls to read_module. This is called automatically if init_mib is used.

add_module_replacement can be used to allow new MIB modules to obsolete older ones, without needing to amend the imports clauses of other modules. It takes the names of the old and new modules, together with an indication of which portions of the old module are affected.

tag len load the new module when:
NULL 0 always (the old module is a strict subset of the new)
name 0 for the given tag only
name non-0 for any identifier with this prefix
It can also be used to handle errors in the module identifiers used in MIB import clauses (such as referring to RFC1213 instead of RFC1213-MIB ).

read_module locates and parses the module specified, together with any modules that it imports from, and adds the contents of these modules to the active MIB tree. Note that add_mibdir must first be called to add the directory containing the file with the module definition, if this is not in the standard path.
By default, the following mib modules will be loaded: IP-MIB, IF-MIB, TCP-MIB, UDP-MIB, SNMPv2-MIB, RFC1213-MIB, UCD-SNMP-MIB. This can be overridden by setting the environment variable MIBS to a (colon-separated) list of modules to load. If this variable starts with a plus character, then the specified modules are added to the default list. Otherwise only those modules listed are loaded (together with any others they import from). If MIBS is set to ALL, read_all_mibs is called to load all the MIB files found in all the specified MIBDIRS.

read_mib parses the file specified, together with any modules that it imports from, and adds the contents to the active MIB tree. Such a file can contain more then one module, though care must be taken that any imports occur earlier in the file, if they are not to be read from the installed modules. Note that the file specified does not need to be in any of the directories initialised by add_mibdir (or the default setup), though any imported modules do.
The environment variable MIBFILES can be set to a (colon-separated) list of files containing mibs to load.

read_objid takes a string containing a textual version of an object identifier (in either numeric or descriptor form), and transforms this into the corresponding list of sub-identifiers. This is returned in the output parameter, with the number of sub-identifiers returned via out_len. When called, out_len must hold the maximum length of the output array. This function returns a value of 1 if it succeeds in parsing the string and 0 otherwise.

get_module_node takes a descriptor and the name of a module, and returns the corresponding oid list, in the same way as read_objid above.
If the module name is specified as "ANY", then this routine will assume that the descriptor given is unique within the tree, and will return the matching entry. If this assumption is invalid, then the behaviour as to which variable is returned is implementation dependent.

shutdown_mib will clear the information that was gathered by read_module, add_mibdir,and add_module_replacement. It is strongly recommended that one does not invoke shutdown_mib while there are SNMP sessions being actively managed.

print_mib will print out a representation of the currently active MIB tree to the specified FILE pointer.

print_variable will take an object identifier (as returned by read_objid or get_module_node ) and an instance of such a variable, and prints out the textual form of the object identifier together with the value of the variable.
A related routine sprint_variable takes an initial parameter of a string buffer, in which to print this information.

print_value and sprint_value do the same as the equivalent print_variable routines, but only displaying the value of the variable, without the corresponding object identifier>

print_objid and sprint_objid
take an object identifier (without an accompanying variable instance) and print out the textual representation.
Note that identifiers lying within the mib-2, experimental or private subtrees are listed from this point onwards, rather than with the full object identifier.

print_description takes an object identifier (as for print_objid above) and prints out the associated description. Note that there is no corresponding routine sprint_description

By default the parser does not save descriptions - they may be huge. In order to be able to print them, you must call snmp_set_save_descriptions(1).

In general the parser is silent about what strangenesses it sees in the mib files. To get warnings reported, call snmp_set_mib_warnings with a parameter of 1 (or 2 for even more warnings).



A colon separated list of directories to search for MIB modules. Default: LIBDIR/snmp/mibs
A colon separated list of files to load. Default: (none)
A colon separated list of MIB modules to load. Default: IP-MIB:IF-MIB:TCP-MIB:UDP-MIB:SNMPv2-MIB:RFC1213-MIB:UCD-SNMP-MIB.






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