.\" Copyright (c) 1999 Tim Singletary
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.\" $FreeBSD: src/lib/libc/db/man/dbm.3,v 1.8 2003/09/08 19:57:13 ru Exp $
.\"
.\" Note: The date here should be updated whenever a non-trivial
.\" change is made to the manual page.
.Dd July 7, 1999
.Dt DBM 3
.Os
.Sh NAME
.Nm dbm_clearerr ,
.Nm dbm_close ,
.Nm dbm_delete ,
.Nm dbm_dirfno ,
.Nm dbm_error ,
.Nm dbm_fetch ,
.Nm dbm_firstkey ,
.Nm dbm_nextkey ,
.Nm dbm_open ,
.Nm dbm_store
.Nd database access functions
.Sh SYNOPSIS
.In ndbm.h
.Ft int
.Fo dbm_clearerr
.Fa "DBM *db"
.Fc
.Ft void
.Fo dbm_close
.Fa "DBM *db"
.Fc
.Ft int
.Fo dbm_delete
.Fa "DBM *db"
.Fa "datum key"
.Fc
.Ft int
.Fo dbm_dirfno
.Fa "DBM *db"
.Fc
.Ft int
.Fo dbm_error
.Fa "DBM *db"
.Fc
.Ft datum
.Fo dbm_fetch
.Fa "DBM *db"
.Fa "datum key"
.Fc
.Ft datum
.Fo dbm_firstkey
.Fa "DBM *db"
.Fc
.Ft datum
.Fo dbm_nextkey
.Fa "DBM *db"
.Fc
.Ft DBM *
.Fo dbm_open
.Fa "const char *file"
.Fa "int open_flags"
.Fa "mode_t file_mode"
.Fc
.Ft int
.Fo dbm_store
.Fa "DBM *db"
.Fa "datum key"
.Fa "datum content"
.Fa "int store_mode"
.Fc
.Sh DESCRIPTION
Database access functions.
These functions are implemented using
.Xr dbopen 3
with a
.Xr hash 3
database.
.Pp
.Vt datum
is declared in
.In ndbm.h :
.Bd -literal
typedef struct {
	char *dptr;
	int dsize;
} datum;
.Ed
.Pp
The
.Fn dbm_open file open_flags file_mode
function
opens or creates a database file.
The
.Fa file
argument
is the basename of the file containing
the database; the actual database has a
.Pa .db
suffix.
I.e., if
.Fa file
is
.Qq Li /home/me/mystuff
then the actual database is in the file
.Pa /home/me/mystuff.db .
The
.Fa open_flags
and
.Fa file_mode
arguments
are passed to
.Xr open 2 .
.Pq Dv O_RDWR | O_CREAT
is a typical value for
.Fa open_flags ;
.Li 0660
is a typical value for
.Fa file_mode .
.Dv O_WRONLY
is treated as O_RDWR in
.Fa open_flags .
The pointer returned by
.Fn dbm_open
identifies the database and is the
.Fa db
argument to the other functions.
The
.Fn dbm_open
function
returns
.Dv NULL
and sets
.Va errno
if there were any errors.
.Pp
The
.Fn dbm_close db
function
closes the database.
The
.Fn dbm_close
function
normally returns zero.
.Pp
The
.Fn dbm_store db key content store_mode
function
inserts or replaces an entry in the database.
The
.Fa store_mode
argument
is either
.Dv DBM_INSERT
or
.Dv DBM_REPLACE .
If
.Fa store_mode
is
.Dv DBM_INSERT
and the database already contains an entry for
.Fa key ,
that entry is not replaced.
Otherwise the entry is replaced or inserted.
The
.Fn dbm_store
function
normally returns zero but returns 1 if the entry could not be
inserted (because
.Fa store_mode
is
.Dv DBM_INSERT ,
and an entry with
.Fa key
already exists) or returns -1 and sets
.Va errno
if there were any errors.
.Pp
The
.Fn dbm_fetch db key
function
returns
.Dv NULL
or the
.Fa content
corresponding to
.Fa key .
.Pp
The
.Fn dbm_delete db key
function
deletes the entry for
.Fa key .
The
.Fn dbm_delete
function
normally returns zero but returns 1 if there was no entry with
.Fa key
in the database or returns -1 and sets
.Va errno
if there were any errors.
.Pp
The
.Fn dbm_firstkey db
function
returns the first key in the database.
The
.Fn dbm_nextkey db
function
returns subsequent keys.
The
.Fn db_firstkey
function
must be called before
.Fn dbm_nextkey .
The order in which keys are returned is unspecified and may appear
random.
The
.Fn dbm_nextkey
function
returns
.Dv NULL
after all keys have been returned.
.Pp
The
.Fn dbm_error db
function
returns the
.Va errno
value of the most recent error.
The
.Fn dbm_clearerr db
function
resets this value to 0 and returns 0.
.Pp
The
.Fn dbm_dirfno db
function
returns the file descriptor to the database.
.Sh LEGACY SYNOPSIS
.Fd #include <fcntl.h>
.Fd #include <ndbm.h>
.Pp
The include file
.In ndbm.h
is necessary for all functions.
.Pp
.Ft DBM *
.br
.Fo dbm_open
.Fa "const char *file"
.Fa "int open_flags"
.Fa "int file_mode"
.Fc ;
.Pp
.Fa file_mode
has type
.Vt int .
.Sh SEE ALSO
.Xr open 2 ,
.Xr dbopen 3 ,
.Xr hash 3 ,
.Xr compat 5
.Sh STANDARDS
These functions (except
.Fn dbm_dirfno )
are included in the
.St -susv2 .