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phpMyFAQ 2.0.10 (Default branch)
01-08-2009
phpMyFAQ is a multilingual, completely database-driven FAQ system. It support various database systems and it also offers a content management system with a WYSIWYG editor, an image manager, flexible multi-user support, a news system, user tracking, language modules, templates, extensive XML support, PDF support, DocBook XML support, a backup system, and an easy to use installation script. |
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dbm(3C) dbm(3C) NAME
dbminit, fetch, store, delete, firstkey, nextkey, dbmclose - database subroutines SYNOPSIS
DESCRIPTION
These functions maintain key/content pairs in a database. They handle very large (a billion blocks (block = 1024 bytes)) databases and can locate a keyed item in one or two file system accesses. key and content parameters are described by the type. A specifies a string of dsize bytes pointed to by dptr. Arbitrary binary data, as well as normal ASCII strings, are allowed. The database is stored in two files. One file is a directory containing a bit map of keys and has as its suffix. The second file contains all data and has as its suffix. Before a database can be accessed, it must be opened by At the time of this call, the files and must exist. (An empty database is created by creating zero-length and files.) Once open, data stored under a key is accessed by and data is placed under a key by Storing data on an existing key replaces the existing data. A key (and its associated contents) is deleted by A linear pass through all keys in a database can be made, in (apparently) random order by using and returns the first key in the database. With any key, returns the next key in the database. The following code can be used to traverse the database: A database can be closed by calling A currently open database must be closed before opening a new one. DIAGNOSTICS
All functions that return an indicate errors with negative values and success with zero. Functions that return a indicate errors with a null dptr. WARNINGS
The dbm functions provided in this library should not be confused in any way with those of a general-purpose database management system such as ALLBASE/HP-UX SQL. These functions provide for multiple search keys per entry, they protect against multi-user access (in other words they do not lock records or files), and they provide the many other useful data base functions that are found in more robust database management systems. Creating and updating databases by use of these functions is relatively slow because of data copies that occur upon hash collisions. These functions for applications requiring fast lookup of relatively static information that is to be indexed by a single key. The file will contain holes so that its apparent size is about four times its actual content. Some older UNIX systems create real file blocks for these holes when touched. These files cannot be copied by normal means (such as cp(1), cat(1), tar(1), or ar(1)) without expan- sion. dptr pointers returned by these subroutines point into static storage that is changed by subsequent calls. The sum of the sizes of a key/content pair must not exceed the internal block size (currently 1024 bytes). Moreover, all key/content pairs that hash together must fit on a single block. returns an error if a disk block fills with inseparable data. does not physically reclaim file space, although it does make it available for reuse. The order of keys presented by and depends on a hashing function, not on anything interesting. A or during a pass through the keys by and may yield unexpected results. AUTHOR
dbm(3C) was developed by the University of California, Berkeley. SEE ALSO
ndbm(3X). dbm(3C)