open.so

berkeley db 4.6.21的源码。berkeley db是一个简单的数据库管理系统

m4_comment([$Id: open.so,v 10.18 2003/10/18 19:15:53 bostic Exp $])

m4_ref_title(Access Methods,
    Database open, @opening a database, am/ops, am/opensub)

m4_p([dnl
The m4_refT(dbh_open) opens a database, and takes five arguments:])

m4_tagbegin

m4_tag(file, [The name of the file to be opened.])

m4_tag(database, [An optional database name.])

m4_tag(type, [dnl
The type of database to open.  This value will be one of the four access
methods m4_db supports: DB_BTREE, DB_HASH, DB_QUEUE or DB_RECNO, or the
special value DB_UNKNOWN, which allows you to open an existing file
without knowing its type.])

m4_tag(mode, [The permissions to give to any created file.])

m4_tagend

m4_p([dnl
There are a few flags that you can set to customize open:])

m4_tagbegin
m4_tag([m4_ref(DB_CREATE)], [dnl
Create the underlying database and any necessary physical files.])

m4_tag([m4_ref(DB_NOMMAP)], [dnl
Do not map this database into process memory.])

m4_tag([m4_ref(DB_RDONLY)], [Treat the data base as read-only.])

m4_tag([m4_ref(DB_THREAD)], [dnl
The returned handle is free-threaded, that is, it can be used
simultaneously by multiple threads within the process.])

m4_tag([m4_ref(DB_TRUNCATE)], [dnl
Physically truncate the underlying database file, discarding all
databases it contained. Underlying filesystem primitives are used to
implement this flag. For this reason it is only applicable to the
physical file and cannot be used to discard individual databases from
within physical files.])

m4_tag([m4_ref(DB_UPGRADE)], [Upgrade the database format as necessary.])

m4_tagend

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