DragonFly On-Line Manual Pages

DBM(3)                DragonFly Library Functions Manual                DBM(3)

NAME
     dbm_clearerr, dbm_close, dbm_delete, dbm_dirfno, dbm_error, dbm_fetch,
     dbm_firstkey, dbm_nextkey, dbm_open, dbm_store - database access
     functions

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <fcntl.h>
     #include <ndbm.h>

     DBM *
     dbm_open(const char *base, int flags, mode_t mode);

     void
     dbm_close(DBM *db);

     int
     dbm_store(DBM *db, datum key, datum data, int flags);

     datum
     dbm_fetch(DBM *db, datum key);

     int
     dbm_delete(DBM *db, datum key);

     datum
     dbm_firstkey(DBM *db);

     datum
     dbm_nextkey(DBM *db);

     int
     dbm_error(DBM *db);

     int
     dbm_clearerr(DBM *db);

     int
     dbm_dirfno(DBM *db);

DESCRIPTION
     Database access functions.  These functions are implemented using
     dbopen(3) with a hash(3) database.

     datum is declared in <ndbm.h>:

     typedef struct {
             char *dptr;
             size_t dsize;
     } datum;

     The dbm_open(base, flags, mode) function opens or creates a database.
     The base argument is the basename of the file containing the database;
     the actual database has a .db suffix.  I.e., if base is
     "/home/me/mystuff" then the actual database is in the file
     /home/me/mystuff.db.  The flags and mode arguments are passed to open(2).
     (O_RDWR | O_CREAT) is a typical value for flags; 0660 is a typical value
     for mode.  O_WRONLY is not allowed in flags.  The pointer returned by
     dbm_open() identifies the database and is the db argument to the other
     functions.  The dbm_open() function returns NULL and sets errno if there
     were any errors.

     The dbm_close(db) function closes the database.

     The dbm_store(db, key, data, flags) function inserts or replaces an entry
     in the database.  The flags argument is either DBM_INSERT or DBM_REPLACE.
     If flags is DBM_INSERT and the database already contains an entry for
     key, that entry is not replaced.  Otherwise the entry is replaced or
     inserted.  The dbm_store() function normally returns zero but returns 1
     if the entry could not be inserted (because flags is DBM_INSERT, and an
     entry with key already exists) or returns -1 and sets errno if there were
     any errors.

     The dbm_fetch(db, key) function returns NULL or the data corresponding to
     key.

     The dbm_delete(db, key) function deletes the entry for key.  The
     dbm_delete() function normally returns zero but returns 1 if there was no
     entry with key in the database or returns -1 and sets errno if there were
     any errors.

     The dbm_firstkey(db) function returns the first key in the database.  The
     dbm_nextkey(db) function returns subsequent keys.  The dbm_firstkey()
     function must be called before dbm_nextkey().  The order in which keys
     are returned is unspecified and may appear random.  The dbm_nextkey()
     function returns NULL after all keys have been returned.

     The dbm_error(db) function returns the errno value of the most recent
     error.  The dbm_clearerr(db) function resets this value to 0 and returns
     0.

     The dbm_dirfno(db) function returns the file descriptor to the database.

SEE ALSO
     open(2), dbopen(3), hash(3)

STANDARDS
     These functions (except dbm_dirfno()) are included in the Version 2 of
     the Single UNIX Specification ("SUSv2").

DragonFly 5.7-DEVELOPMENT     September 13, 2019     DragonFly 5.7-DEVELOPMENT