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Manual Reference Pages  -  NDB (3)

NAME

ndbopen, ndbcat, ndbchanged, ndbclose, ndbreopen, ndbsearch, ndbsnext, ndbgetvalue, ndbfree, ipattr, ndbgetipaddr, ndbipinfo, ndbhash, ndbparse, ndbfindattr, ndbdiscard, ndbconcatenate, ndbreorder, ndbsubstitute, ndbgetval, ndblookval - network database

CONTENTS

Synopsis
Description
Files
Source
See Also
Diagnostics
Bugs

SYNOPSIS

#include <u.h>
#include <libc.h>
#include <bio.h>
#include <ndb.h>

Ndb*      ndbopen(char *file)

Ndb*      ndbcat(Ndb *db1, Ndb *db2)

Ndb*      ndbchanged(Ndb *db)

int       ndbreopen(Ndb *db)

void      ndbclose(Ndb *db)

Ndbtuple* ndbsearch(Ndb *db, Ndbs *s, char *attr, char *val)

Ndbtuple* ndbsnext(Ndbs *s, char *attr, char *val)

char*     ndbgetvalue(Ndb *db, Ndbs *s, char *attr, char *val,

          char *rattr, Ndbtuple **tp)

char*     ipattr(char *name)

Ndbtuple* ndbgetipaddr(Ndb *db, char *sys);

Ndbtuple* ndbipinfo(Ndb *db, char *attr, char *val, char **attrs,
int nattr)

ulong     ndbhash(char *val, int hlen)

Ndbtuple* ndbparse(Ndb *db)

Ndbtuple* ndbfindattr(Ndbtuple *entry, Ndbtuple *line, char *attr)

void      ndbfree(Ndbtuple *db)

Ndbtuple* ndbdiscard(Ndbtuple *t, Ndbtuple *a)

Ndbtuple* ndbconcatenate(Ndbtuple *a, Ndbtuple *b);

Ndbtuple* ndbreorder(Ndbtuple *t, Ndbtuple *a);

Ndbtuple* ndbsubstitute(Ndbtuple *t, Ndbtuple *from, Ndbtuple *to);

DESCRIPTION

These routines are used by network administrative programs to search the network database. They operate on the database files described in ndb(7).

Ndbopen opens the database file and calls malloc(3) to allocate a buffer for it. If file is zero, all network database files are opened.

Ndbcat concatenates two open databases. Either argument may be nil.

Ndbreopen checks if the database files associated with db have changed and if so throws out any cached information and reopens the files.

Ndbclose closes any database files associated with db and frees all storage associated with them.

Ndbsearch and ndbsnext search a database for an entry containing the attribute/value pair, attr=val. Ndbsearch is used to find the first match and ndbsnext is used to find each successive match. On a successful search both return a linked list of Ndbtuple structures acquired by malloc(3) that represent the attribute/value pairs in the entry. On failure they return zero.
typedef struct Ndbtuple Ndbtuple; struct Ndbtuple {
char attr[Ndbalen];
char *val;
Ndbtuple *entry;
Ndbtuple *line;
ulong ptr; /* for the application; starts 0 */
char valbuf[Ndbvlen]; /* initial allocation for val */ };
The entry pointers chain together all pairs in the entry in a null-terminated list. The line pointers chain together all pairs on the same line in a circular list. Thus, a program can implement 2 levels of binding for pairs in an entry. In general, pairs on the same line are bound tighter than pairs on different lines.
The argument s of ndbsearch has type Ndbs and should be pointed to valid storage before calling ndbsearch, which will fill it with information used by ndbsnext to link successive searches. The structure Ndbs looks like:
typedef struct Ndbs Ndbs; struct Ndbs {
Ndb *db; /* data base file being searched */
...
Ndbtuple *t; /* last attribute value pair found */ };
The t field points to the pair within the entry matched by the ndbsearch or ndbsnext.
Ndbgetvalue searches the database for an entry containing not only an attribute/value pair, attr=val, but also a pair with the attribute rattr. If successful, it returns a malloced copy of the null terminated value associated with rattr. If tp is non nil, *tp will point to the entry. Otherwise the entry will be freeed.
Ndbfree frees a list of tuples returned by one of the other routines.
Ipattr takes the name of an IP system and returns the attribute it corresponds to:
 
dom domain name
ip Internet number
sys system name
Ndbgetipaddr looks in db for an entry matching sys as the value of a sys= or dom= attribute/value pair and returns all IP addresses in the entry. If sys is already an IP address, a tuple containing just that address is returned.

Ndbipinfo looks up Internet protocol information about a system. This is an IP aware search. It looks first for information in the system’s database entry and then in the database entries for any IP subnets or networks containing the system. The system is identified by the attribute/value pair, attr=val. Ndbipinfo returns a list of tuples whose attributes match the attributes in the n element array attrs. For example, consider the following database entries describing a network, a subnetwork, and a system.

ipnet=big ip=10.0.0.0
          dns=dns.big.com
          smtp=smtp.big.com ipnet=dept ip=10.1.1.0 ipmask=255.255.255.0
          smtp=smtp1.big.com ip=10.1.1.4 dom=x.big.com
          bootf=/386/9pc

Calling

ndbipinfo(db, "dom", "x.big.com", ["bootf" "smtp" "dns"], 3)

will return the tuples bootf=/386/9pc, smtp=smtp1.big.com, and dns=dns.big.com.

The next three routines are used by programs that create the hash tables and database files. Ndbhash computes a hash offset into a table of length hlen for the string val. Ndbparse reads and parses the next entry from the database file. Multiple calls to ndbparse parse sequential entries in the database file. A zero is returned at end of file.

Ndbfindattr searches entry for the tuple with attribute attr and returns a pointer to the tuple. If line points to a particular line in the entry, the search starts there and then wraps around to the beginning of the entry.

All of the routines provided to search the database provide an always consistent view of the relevant files. However, it may be advantageous for an application to read in the whole database using ndbopen and ndbparse and provide its own search routines. The ndbchanged routine can be used by the application to periodicly check for changes. It returns zero if none of the files comprising the database have changes and non-zero if they have.

Finally, a number of routines are provided for manipulating tuples.

Ndbdiscard removes attr/val pair a from tuple t and frees it. If a isn’t in t it is just freed.

Ndbconcatenate concatenates two tuples and returns the result. Either or both tuples may be nil.

Ndbreorder reorders a tuple t to make the line containing attr/val pair a first in the entry and making a first in its line.

Ndbsubstitute replaces a single att/val pair from in t with the tuple to. All attr/val pairs in to end up on the same line. from is freed.

FILES

/usr/local/plan9/ndb
  directory of network database files

SOURCE

/usr/local/plan9/src/libndb

SEE ALSO

ndb(1) ndb(7)

DIAGNOSTICS

Ndbgetvalue and ndblookvalue set errstr to buffer too short if the buffer provided isn’t long enough for the returned value.

BUGS

Ndbgetval and ndblookval are deprecated versions of ndbgetvalue and ndblookvalue. They expect a fixed 64 byte long result buffer and existed when the values of a Ndbtuple structure where fixed length.
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