NDB(3)                                                     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

     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)

     NDB(3)                                                     NDB(3)

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

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

          Ndbtuple*  ndbsubstitute(Ndbtuple *t, Ndbtuple *from, Ndbtu-
          ple *to);

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

          Ndbopen opens the database file and calls malloc(3) to allo-
          cate 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 con-
          taining 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 pro-
          gram 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

     NDB(3)                                                     NDB(3)

          pointed to valid storage before calling ndbsearch, which
          will fill it with information used by ndbsnext to link suc-
          cessive 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 mal-
          loced copy of the null terminated value associated with
          rattr. If tp is non nil, *tp will point to the entry.  Oth-
          erwise 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

     NDB(3)                                                     NDB(3)

                     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
          /ndb directory of network database files

     NDB(3)                                                     NDB(3)

     SOURCE
          /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.