gdbm - phpMan

File: gdbm.info, Node: Top, Next: Copying, Up: (dir)

The GNU database manager.
*************************

GNU `dbm' is a library of functions implementing a hashed database on a
disk file. This manual documents GNU `dbm' Version 1.10 (`gdbm'). The
software was originally written by Philip A. Nelson. This document
was originally written by Pierre Gaumond from texts written by Phil.

* Menu:

Introduction:

* Copying:: Your rights.
* Intro:: Introduction to GNU dbm.
* List:: List of functions.

Functions:

* Open:: Opening the database.
* Close:: Closing the database.
* Store:: Inserting and replacing records in the database.
* Fetch:: Searching records in the database.
* Delete:: Removing records from the database.
* Sequential:: Sequential access to records.
* Reorganization:: Database reorganization.
* Sync:: Insure all writes to disk have competed.
* Flat files:: Export and import to Flat file format.
* Errors:: Convert internal error codes into English.
* Options:: Setting internal options.
* Locking:: File locking.

Programs

* testgdbm:: Test and modify a GDBM database.
* gdbmexport:: Export a database into a portable format.

Other topics:

* Error codes:: Error codes returned by `gdbm' calls.
* Variables:: Two useful variables.
* Compatibility:: Compatibility with UNIX dbm and ndbm.
* Bugs:: Problems and bugs.
* Resources:: Additional resources,

* GNU Free Documentation License:: Document license.
* Index:: Index

File: gdbm.info, Node: Copying, Next: Intro, Prev: Top, Up: Top

1 Copying Conditions.
*********************

This library is "free"; this means that everyone is free to use it and
free to redistribute it on a free basis. GNU `dbm' (`gdbm') is not in
the public domain; it is copyrighted and there are restrictions on its
distribution, but these restrictions are designed to permit everything
that a good cooperating citizen would want to do. What is not allowed
is to try to prevent others from further sharing any version of `gdbm'
that they might get from you.

Specifically, we want to make sure that you have the right to give
away copies `gdbm', that you receive source code or else can get it if
you want it, that you can change these functions or use pieces of them
in new free programs, and that you know you can do these things.

To make sure that everyone has such rights, we have to forbid you to
deprive anyone else of these rights. For example, if you distribute
copies `gdbm', you must give the recipients all the rights that you
have. You must make sure that they, too, receive or can get the source
code. And you must tell them their rights.

Also, for our own protection, we must make certain that everyone
finds out that there is no warranty for anything in the `gdbm'
distribution. If these functions are modified by someone else and
passed on, we want their recipients to know that what they have is not
what we distributed, so that any problems introduced by others will not
reflect on our reputation.

`Gdbm' is currently distributed under the terms of the GNU General
Public License, Version 3. (_NOT_ under the GNU General Library Public
License.) A copy the GNU General Public License is included with the
distribution of `gdbm'.

File: gdbm.info, Node: Intro, Next: List, Prev: Copying, Up: Top

2 Introduction to GNU `dbm'.
****************************

GNU `dbm' (`gdbm') is a library of database functions that use
extensible hashing and works similar to the standard UNIX `dbm'
functions. These routines are provided to a programmer needing to
create and manipulate a hashed database. (`gdbm' is _NOT_ a complete
database package for an end user.)

The basic use of `gdbm' is to store key/data pairs in a data file.
Each key must be unique and each key is paired with only one data item.
The keys can not be directly accessed in sorted order. The basic unit
of data in `gdbm' is the structure:

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

This structure allows for arbitrary sized keys and data items.

The key/data pairs are stored in a `gdbm' disk file, called a `gdbm'
database. An application must open a `gdbm' database to be able
manipulate the keys and data contained in the database. `gdbm' allows
an application to have multiple databases open at the same time. When
an application opens a `gdbm' database, it is designated as a `reader'
or a `writer'. A `gdbm' database can be opened by at most one writer
at a time. However, many readers may open the database simultaneously.
Readers and writers can not open the `gdbm' database at the same time.

File: gdbm.info, Node: List, Next: Open, Prev: Intro, Up: Top

3 List of functions.
********************

The following is a quick list of the functions contained in the `gdbm'
library. The include file `gdbm.h', that can be included by the user,
contains a definition of these functions.

#include <gdbm.h>

GDBM_FILE gdbm_open(name, block_size, flags, mode, fatal_func);
void gdbm_close(dbf);
int gdbm_store(dbf, key, content, flag);
datum gdbm_fetch(dbf, key);
int gdbm_delete(dbf, key);
datum gdbm_firstkey(dbf);
datum gdbm_nextkey(dbf, key);
int gdbm_reorganize(dbf);
void gdbm_sync(dbf);
int gdbm_exists(dbf, key);
char *gdbm_strerror(errno);
int gdbm_setopt(dbf, option, value, size);
int gdbm_fdesc(dbf);

The `gdbm.h' include file is often in the `/usr/local/include'
directory. (The actual location of `gdbm.h' depends on your local
installation of `gdbm'.)

File: gdbm.info, Node: Open, Next: Close, Prev: List, Up: Top

4 Opening the database.
***********************

-- gdbm interface: GDBM_FILE gdbm_open (const char *NAME, int
BLOCK_SIZE, int FLAGS, int MODE, void (*fatal_func)(const
char *))
Initializes `gdbm' system. If the file has a size of zero bytes,
a file initialization procedure is performed, setting up the
initial structure in the file.

The arguments are:

NAME
The name of the file (the complete name, `gdbm' does not
append any characters to this name).

BLOCK_SIZE
It is used during initialization to determine the size of
various constructs. It is the size of a single transfer from
disk to memory. This parameter is ignored if the file has
been previously initialized. The minimum size is 512. If
the value is less than 512, the file system block size is
used, otherwise the value of BLOCK_SIZE is used.

FLAGS
If `flags' is set to `GDBM_READER', the user wants to just
read the database and any call to `gdbm_store' or
`gdbm_delete' will fail. Many readers can access the
database at the same time. If `flags' is set to
`GDBM_WRITER', the user wants both read and write access to
the database and requires exclusive access. If `flags' is set
to `GDBM_WRCREAT', the user wants both read and write access
to the database and wants it created if it does not already
exist. If `flags' is set to `GDBM_NEWDB', the user want a
new database created, regardless of whether one existed, and
wants read and write access to the new database.

The following may also be logically or'd into the database
flags: `GDBM_SYNC', which causes all database operations to be
synchronized to the disk, `GDBM_NOLOCK', which prevents the
library from performing any locking on the database file, and
`GDBM_NOMMAP', which disables the memory mapping mechanism.
The option `GDBM_FAST' is now obsolete, since `gdbm' defaults
to no-sync mode.

If the host `open' call (*note open: (open(2))open.)
supports the `O_CLOEXEC' flag, the `GDBM_CLOEXEC' can be or'd
into the flags, to enable the close-on-exec flag for the
database file descriptor.

MODE
File mode (see *note change permissions of a file:
(chmod(2))chmod, and *note open a file: (open(2))open.),
which is used if the file is created).

FATAL_FUNC
A function for `gdbm' to call if it detects a fatal error.
The only parameter of this function is a string. If the
value of `NULL' is provided, `gdbm' will use a default
function.

The return value, is the pointer needed by all other functions to
access that `gdbm' file. If the return is the `NULL' pointer,
`gdbm_open' was not successful. The errors can be found in
`gdbm_errno' variable (*note gdbm_errno: Variables.). Available
error codes are discussed in *note Error codes::.

In all of the following calls, the parameter DBF refers to the
pointer returned from `gdbm_open'.

File: gdbm.info, Node: Close, Next: Store, Prev: Open, Up: Top

5 Closing the database.
***********************

It is important that every file opened is also closed. This is needed
to update the reader/writer count on the file:

-- gdbm interface: void gdbm_close (GDBM_FILE DBF)
This function closes the `gdbm' file and frees all memory
associated with it. The parameter is:

DBF
The pointer returned by `gdbm_open'.

File: gdbm.info, Node: Store, Next: Fetch, Prev: Close, Up: Top

6 Inserting and replacing records in the database.
**************************************************

-- gdbm interface: int gdbm_store (GDBM_FILE DBF, datum KEY, datum
CONTENT, int FLAG)
The function `gdbm_store' inserts or replaces records in the
database.

The parameters are:

DBF
The pointer returned by `gdbm_open'.

KEY
The search key.

CONTENT
The data to be associated with the key.

FLAG
Defines the action to take when the key is already in the
database. The value `GDBM_REPLACE' (defined in `gdbm.h')
asks that the old data be replaced by the new CONTENT. The
value `GDBM_INSERT' asks that an error be returned and no
action taken if the KEY already exists.

This function can return the following values:

-1
The item was not stored in the database because the caller
was not an official writer or either KEY or CONTENT have a
`NULL' `dptr' field.

Both KEY and CONTENT must have the `dptr' field be a
non-`NULL' value. Since a `NULL' `dptr' field is used by
other functions to indicate an error, it cannot be valid data.

+1
The item was not stored because the argument FLAG was
`GDBM_INSERT' and the KEY was already in the database.

0
No error. The value of CONTENT is keyed by KEY. The file on
disk is updated to reflect the structure of the new database
before returning from this function.

If you store data for a KEY that is already in the data base, `gdbm'
replaces the old data with the new data if called with `GDBM_REPLACE'.
You do not get two data items for the same `key' and you do not get an
error from `gdbm_store'.

The size in `gdbm' is not restricted like `dbm' or `ndbm'. Your
data can be as large as you want.

File: gdbm.info, Node: Fetch, Next: Delete, Prev: Store, Up: Top

7 Searching for records in the database.
****************************************

-- gdbm interface: datum gdbm_fetch (GDBM_FILE DBF, datum KEY)
Looks up a given KEY and returns the information associated with
it. The `dptr' field in the structure that is returned points to a
memory block allocated by `malloc'. It is the caller's
responsibility to free it when no longer needed.

If the `dptr' is `NULL', no data was found.

The parameters are:

DBF
The pointer returned by `gdbm_open'.

KEY
The search key.

An example of using this function:

content = gdbm_fetch (dbf, key);
if (content.dptr == NULL)
{
fprintf(stderr, "key not found\n");
}
else
{
/* do something with content.dptr */
}

You may also search for a particular key without retrieving it:

-- gdbm interface: int gdbm_exists (GDBM_FILE DBF, datum KEY)
Returns `true' (`1') if the KEY exists in DBF and `false' (`0')
otherwise.

The parameters are:

DBF
The pointer returned by `gdbm_open'.

KEY
The search key.

File: gdbm.info, Node: Delete, Next: Sequential, Prev: Fetch, Up: Top

8 Removing records from the database.
*************************************

To remove some data from the database, use the `gdbm_delete' function.

-- gdbm interface: int gdbm_delete (GDBM_FILE DBF, datum KEY)
Deletes the data associated with the given KEY, if it exists in
the database DBF. The file on disk is updated to reflect the
structure of the new database before returning from this function.

The parameters are:

DBF
The pointer returned by `gdbm_open'.

DATUM KEY
The search key.

The function returns `-1' if the item is not present or the
requester is a reader. The return of `0' marks a successful
delete.

File: gdbm.info, Node: Sequential, Next: Reorganization, Prev: Delete, Up: Top

9 Sequential access to records.
*******************************

The next two functions allow for accessing all items in the database.
This access is not `key' sequential, but it is guaranteed to visit every
`key' in the database once. The order has to do with the hash values.
`gdbm_firstkey' starts the visit of all keys in the database.
`gdbm_nextkey' finds and reads the next entry in the hash structure for
`dbf'.

-- gdbm interface: datum gdbm_firstkey (GDBM_FILE DBF)
Initiate sequential access to the database DBF. The returned
value is the first key accessed in the database. If the `dptr'
field in the returned datum is `NULL', the database contains no
data.

Otherwise, `dptr' points to a memory block obtained from `malloc',
which holds the key value. The caller is responsible for freeing
this memory block when no longer needed.

-- gdbm interface: datum gdbm_nextkey (GDBM_FILE DBF, datum PREV)
This function continues the iteration over the keys in DBF,
initiated by `gdbm_firstkey'. The parameter PREV holds the value
returned from a previous call to `gdbm_nextkey' or `gdbm_firstkey'.

The function returns next key from the database. If the `dptr'
field in the returned datum is `NULL', all keys in the database
has been visited.

Otherwise, `dptr' points to a memory block obtained from `malloc',
which holds the key value. The caller is responsible for freeing
this memory block when no longer needed.

These functions were intended to visit the database in read-only
algorithms, for instance, to validate the database or similar
operations. The usual algorithm for sequential access is:

key = gdbm_firstkey (dbf);
while (key.dptr)
{
datum nextkey;

/* do something with the key */
...

/* Obtain the next key */
nextkey = gdbm_nextkey (dbf, key);
/* Reclaim the memory used by the key */
free (key.dptr);
/* Use nextkey in the next iteration. */
key = nextkey;
}

Care should be taken when the `gdbm_delete' function is used in such
a loop. File visiting is based on a "hash table". The `gdbm_delete'
function re-arranges the hash table to make sure that any collisions in
the table do not leave some item "un-findable". The original key order
is _not_ guaranteed to remain unchanged in all instances. So it is
possible that some key will not be visited if a loop like the following
is executed:

key = gdbm_firstkey (dbf);
while (key.dptr)
{
datum nextkey;
if (some condition)
{
gdbm_delete (dbf, key);
}
nextkey = gdbm_nextkey (dbf, key);
free (key.dptr);
key = nextkey;
}

File: gdbm.info, Node: Reorganization, Next: Sync, Prev: Sequential, Up: Top

10 Database reorganization.
***************************

The following function should be used very seldom.

-- gdbm interface: int gdbm_reorganize (GDBM_FILE DBF)
Reorganizes the database.

The parameter is:

DBF
The pointer returned by `gdbm_open'.

If you have had a lot of deletions and would like to shrink the space
used by the `gdbm' file, this function will reorganize the database.
This results, in particular, in shortening the length of a `gdbm' file
by removing the space occupied by deleted records.

This reorganization requires creating a new file and inserting all
the elements in the old file DBF into the new file. The new file is
then renamed to the same name as the old file and DBF is updated to
contain all the correct information about the new file. If an error is
detected, the return value is negative. The value zero is returned
after a successful reorganization.

File: gdbm.info, Node: Sync, Next: Flat files, Prev: Reorganization, Up: Top

11 Database Synchronization
***************************

Unless your database was opened with the `GDBM_SYNC' flag, `gdbm' does
not wait for writes to be flushed to the disk before continuing. This
allows for faster writing of databases at the risk of having a
corrupted database if the application terminates in an abnormal
fashion. The following function allows the programmer to make sure the
disk version of the database has been completely updated with all
changes to the current time.

-- gdbm interface: void gdbm_sync (GDBM_FILE DBF)
Synchronizes the changes in DBF with its disk file. The parameter
is a pointer returned by `gdbm_open'.

This function would usually be called after a complete set of
changes have been made to the database and before some long
waiting time. The `gdbm_close' function automatically calls the
equivalent of `gdbm_sync' so no call is needed if the database is
to be closed immediately after the set of changes have been made.

File: gdbm.info, Node: Flat files, Next: Errors, Prev: Sync, Up: Top

12 Export and Import
********************

`Gdbm' databases can be converted into a portable "flat format". This
format can be used, for example, to migrate between the different
versions of `gdbm' databases. Generally speaking, flat files are safe
to send over the network, and can be used to recreate the database on
another machine. The recreated database is guaranteed to be a
byte-to-byte equivalent of the database from which the flat file was
created. This does not necessarily mean, however, that this file can
be used in the same way as the original one. For example, if the
original database contained non-ASCII data (e.g. C structures,
integers etc.), the recreated database can be of any use only if the
target machine has the same integer size and byte ordering as the
source one and if its C compiler uses the same packing conventions as
the one which generated C which populated the original database. In
general, such binary databases are not portable between machines,
unless you follow some stringent rules on what data is written to them
and how it is interpreted.

-- gdbm interface: int gdbm_export (GDBM_FILE DBF, const char
*EXPORTFILE, int FLAG, int MODE)
Create a flat file from the `gdbm' database. The parameters are:

DBF
A pointer to the source database, returned by a call to
`gdbm_open'. The database must be open in `GDBM_WRITER' mode.

EXPORTFILE
The name of the output file.

FLAG
How to create the output file. If FLAG is `GDBM_WRCREAT',
the file will be created if it does not exist already.
Otherwise, if it is `GDBM_NEWDB', it will be created if it
does not exist, and truncated otherwise.

MODE
The permissions to use when creating the output file. See
*note open a file: (open(2))open, for a detailed discussion.

-- gdbm interface: int gdbm_import (GDBM_FILE DBF, const char
*IMPORTFILE, int FLAG)
Populates the database from an existing flat file.

DBF
A pointer to the source database, returned by a call to
`gdbm_open'. The database must be open in `GDBM_WRITER' mode.

IMPORTFILE
The name of the input flat file. The file must exist.

FLAG
The FLAG argument to be passed to `gdbm_store' function when
adding new records. *Note Store::, for a description of its
effect.

See also *note gdbmexport::, *note testgdbm export::, and *note
testgdbm import::.

File: gdbm.info, Node: Errors, Next: Options, Prev: Flat files, Up: Top

13 Error strings.
*****************

To convert a `gdbm' error code into English text, use this routine:

-- gdbm interface: const char * gdbm_strerror (gdbm_error ERRNO)
Converts ERRNO (which is an integer value) into a human-readable
descriptive text. Returns a pointer to a static string. The
caller must not alter or free the returned pointer.

The ERRNO argument is usually the value of the global variable
`gdbm_errno'. *Note gdbm_errno: Variables.

File: gdbm.info, Node: Options, Next: Locking, Prev: Errors, Up: Top

14 Setting options
******************

`Gdbm' supports the ability to set certain options on an already open
database.

-- gdbm interface: int gdbm_setopt (GDBM_FILE DBF, int OPTION, void
*VALUE, int SIZE)
Sets an option on the database or returns the value of an option.

The parameters are:

DBF
The pointer returned by `gdbm_open'.

OPTION
The option to be set or retreived.

VALUE
A pointer to the value to which OPTION will be set or where to
place the option value (depending on the option).

SIZE
The length of the data pointed to by VALUE.

The valid options are:

GDBM_SETCACHESIZE
GDBM_CACHESIZE
Set the size of the internal bucket cache. This option may only be
set once on each GDBM_FILE descriptor, and is set automatically to
100 upon the first access to the database. The VALUE should point
to a `size_t' holding the desired cache size.

The `GDBM_CACHESIZE' option is provided for compatibility with
earlier versions.

GDBM_GETCACHESIZE
Return the size of the internal bucket cache. The VALUE should
point to a `size_t' variable, where the size will be stored.

GDBM_GETFLAGS
Return the flags describing the state of the database. The VALUE
should point to a `int' variable where to store the flags. The
return is the same as the flags used when opening the database
(*note gdbm_open: Open.), except that it reflects the current
state (which may have been altered by another calls to
`gdbm_setopt'.

GDBM_FASTMODE
Enable or disable the "fast writes mode", i.e. writes without
subsequent synchronization. The VALUE should point to an integer:
`TRUE' to enable fast mode, and `FALSE' to disable it.

This option is retained for compatibility with previous versions of
`gdbm'. Its effect is the reverse of `GDBM_SETSYNCMODE' (see
below).

GDBM_SETSYNCMODE
GDBM_SYNCMODE
Turn on or off file system synchronization operations. This
setting defaults to off. The VALUE should point to an integer:
`TRUE' to turn synchronization on, and `FALSE' to turn it off.

Note, that this option is a reverse of `GDBM_FASTMODE', i.e.
calling `GDBM_SETSYNCMODE' with `TRUE' has the same effect as
calling `GDBM_FASTMODE' with `FALSE'.

The `GDBM_SYNCMODE' option is provided for compatibility with
earlier versions.

GDBM_GETSYNCMODE
Return the current synchronization status. The VALUE should point
to an `int' where the status will be stored.

GDBM_SETCENTFREE
GDBM_CENTFREE
_NOTICE: This feature is still under study._

Set central free block pool to either on or off. The default is
off, which is how previous versions of `gdbm' handled free blocks.
If set, this option causes all subsequent free blocks to be placed
in the _global_ pool, allowing (in theory) more file space to be
reused more quickly. The VALUE should point to an integer: `TRUE'
to turn central block pool on, and `FALSE' to turn it off.

The `GDBM_CENTFREE' option is provided for compatibility with
earlier versions.

GDBM_SETCOALESCEBLKS
GDBM_COALESCEBLKS
_NOTICE: This feature is still under study._

Set free block merging to either on or off. The default is off,
which is how previous versions of `gdbm' handled free blocks. If
set, this option causes adjacent free blocks to be merged. This
can become a CPU expensive process with time, though, especially if
used in conjunction with GDBM_CENTFREE. The VALUE should point to
an integer: `TRUE' to turn free block merging on, and `FALSE' to
turn it off.

GDBM_GETCOALESCEBLKS
Return the current status of free block merging. The VALUE should
point to an `int' where the status will be stored.

GDBM_SETMAXMAPSIZE
Sets maximum size of a memory mapped region. The VALUE should
point to a value of type `size_t', `unsigned long' or `unsigned'.
The actual value is rounded to the nearest page boundary (the page
size is obtained from `sysconf(_SC_PAGESIZE)').

GDBM_GETMAXMAPSIZE
Return the maximum size of a memory mapped region. The VALUE
should point to a value of type `size_t' where to return the data.

GDBM_SETMMAP
Enable or disable memory mapping mode. The VALUE should point to
an integer: `TRUE' to enable memory mapping or `FALSE' to disable
it.

GDBM_GETMMAP
Check whether memory mapping is enabled. The VALUE should point
to an integer where to return the status.

GDBM_GETDBNAME
Return the name of the database disk file. The VALUE should point
to a variable of type `char**'. A pointer to the newly allocated
copy of the file name will be placed there. The caller is
responsible for freeing this memory when no longer needed. For
example:

char *name;

if (gdbm_setopt (dbf, GDBM_GETDBNAME, &name, sizeof (name)))
{
fprintf (stderr, "gdbm_setopt failed: %s\n",
gdbm_strerror (gdbm_errno));
}
else
{
printf ("database name: %s\n", name);
free (name);
}

The return value will be `-1' upon failure, or `0' upon success.
The global variable `gdbm_errno' will be set upon failure.

For instance, to set a database to use a cache of 10, after opening
it with `gdbm_open', but prior to accessing it in any way, the following
code could be used:

int value = 10;
ret = gdbm_setopt (dbf, GDBM_CACHESIZE, &value, sizeof (int));

File: gdbm.info, Node: Locking, Next: testgdbm, Prev: Options, Up: Top

15 File Locking.
****************

With locking disabled (if `gdbm_open' was called with `GDBM_NOLOCK'),
the user may want to perform their own file locking on the database file
in order to prevent multiple writers operating on the same file
simultaneously.

In order to support this, the `gdbm_fdesc' routine is provided.

-- gdbm interface: int gdbm_fdesc (GDBM_FILE DBF)
Returns the file descriptor of the database DBF. This value can
be used as an argument to `flock', `lockf' or similar calls.

File: gdbm.info, Node: testgdbm, Next: gdbmexport, Prev: Locking, Up: Top

16 Test and modify a GDBM database.
***********************************

The `testgdbm' utility allows you to view and modify an existing GDBM
database or to create a new one.

When invoked without options, it tries to open a database file called
`junk.gdbm', located in the current working directory. You can change
this default using the `-g' command line option. This option takes a
single argument, specifying the file name to open, e.g.:

$ testgdbm -g file.db

The database will be opened in read-write mode, unless the `-r'
option is specified, in which case it will be opened only for reading.

If the database does not exist, `testgdbm' will create it. There is
a special option `-n', which instructs the utility to create a new
database. If it is used and if the database already exists, it will be
deleted, so use it sparingly.

* Menu:

* invocation::
* shell::

File: gdbm.info, Node: invocation, Next: shell, Up: testgdbm

16.1 testgdbm invocation
========================

The following table summarizes all `testgdbm' command line options:

`-b SIZE'
Set block size.

`-c SIZE'
Set cache size.

`-g FILE'
Operate on FILE instead of the default `junk.gdbm'.

`-h'
Print a concise help summary.

`-n'
Create the database.

`-r'
Open the database in read-only mode.

`-s'
Synchronize to the disk after each write.

`-v'
Print program version and licensing information and exit.

File: gdbm.info, Node: shell, Prev: invocation, Up: testgdbm

16.2 testgdbm interactive mode
==============================

After successful startup, `testgdbm' starts a loop, in which it reads
commands from the user, executes them and prints the results on the
standard output. If the standard input is attached to a console,
`testgdbm' runs in interactive mode, which is indicated by its "prompt":

testgdbm> _

The utility finishes when it reads the `quit' command (see below) or
detects end-of-file on its standard input, whichever occurs first.

A `testgdbm' command consists of a "command verb", optionally
followed by one or two "arguments", separated by any amount of white
space. A command verb can be entered either in full or in an
abbreviated form, as long as that abbreviation does not match any other
verb. For example, `co' can be used instead of `count' and `ca'
instead of `cache'. Furthermore, many command verbs also have
single-letter forms, called "command letters".

An argument is any sequence of non-whitespace characters. Notice,
that currently there is no way to enter arguments containing white
space. This limitation will be removed in future releases.

Each command takes at most two "formal parameters", which can be
optional or mandatory. If the number of actual arguments is less than
the number of mandatory parameters, `testgdbm' will prompt you to
supply missing arguments. For example, the `store' command takes two
mandatory parameters, so if you invoked it with no arguments, you would
be prompted twice to supply the necessary data, as shown in example
below:

testgdbm> store
key> three
data> 3

However, such prompting is possible only in interactive mode. In
non-interactive mode (e.g. when running a script), all arguments must
be supplied with each command, otherwise `testgdbm' will report an
error and exit immediately.

Some commands produce excessive amounts of output. To help you
follow it, `testgdbm' uses a pager utility to display such output. The
name of the pager utility is taken from the environment variable
`PAGER'. The pager is invoked only in interactive mode and only if the
estimated number of output lines is greater then the number of lines on
your screen.

Many of the `testgdbm' commands operate on database key and data
values. The utility assumes that both keys and data are ASCII strings,
either nul-terminated or not. By default, it is assumed that strings
are nul-terminated. You can change this by using `z' (`key-zero', for
keys) and `Z' (`data-zero', for data) commands.

The following table summarizes all available commands:

-- command verb: count
-- command abbrev: co
-- command letter: c
Print the number of entries in the database.

-- command verb: delete KEY
-- command abbrev: de KEY
-- command letter: d KEY
Delete entry with a given KEY

-- command verb: export FILE-NAME [truncate]
-- command abbrev: e FILE-NAME [truncate]
Export the database to the flat file FILE-NAME. *Note Flat
files::, for a description of the flat file format and its
purposes. This command will not overwrite an existing file,
unless the word `truncate' is given as its second argument.

See also `first', below.

*Note Sequential::, for more information on sequential access.

-- command verb: quit
-- command abbrev: q
Close the database and quit the utility.

-- command verb: store KEY DATA
-- command abbrev: sto KEY DATA
-- command letter: s KEY DATA
Store the DATA with KEY in the database. If KEY already exists,
its data will be replaced.

-- command verb: first
-- command abbrev: fi
-- command letter: 1
Fetch and display the first record in the database. Subsequent
records can be fetched using `next' command (see above). *Note
Sequential::, for more information on sequential access.

-- command verb: read FILE [replace]
-- command abbrev: rea FILE [replace]
-- command letter: < FILE [replace]
Read entries from FILE and store them in the database. If the
word `replace' is given as the second argument, any existing
records with matching keys will be replaced.

-- command verb: reorganize
-- command abbrev: reo
-- command letter: r
Reorganize the database (*note Reorganization::).

-- command verb: key-zero
-- command abbrev: k
-- command letter: z
Toggle key nul-termination. Use `status' to inspect the current
state. *Note nul-termination::.

-- command verb: avail
-- command abbrev: a
-- command letter: A
Print the "avail list".

-- command verb: bucket
-- command abbrev: b
-- command letter: B
Print the bucket number NUM.

-- command verb: current
-- command abbrev: cu
-- command letter: C
Print the current bucket.

-- command verb: dir
-- command abbrev: di
-- command letter: D
Print hash directory.

-- command verb: header
-- command abbrev: hea
-- command letter: F
Print file header.

-- command verb: hash KEY
-- command abbrev: ha KEY
-- command letter: H KEY
Compute and display the hash value for the given KEY.

-- command verb: cache
-- command abbrev: ca
-- command letter: K
Print the bucket cache.

-- command verb: status
-- command abbrev: sta
-- command letter: S
Print current program status. The following example shows the
information displayed:

Database file: junk.gdbm
Zero terminated keys: yes
Zero terminated data: yes

-- command verb: version
-- command abbrev: v
Print the version of `gdbm'.

-- command verb: data-zero
-- command abbrev: da
-- command letter: Z
Toggle data nul-termination. Use `status' to examine the current
status.

*Note nul-termination::.

-- command verb: help
-- command abbrev: hel
-- command letter: ?
Print a concise command summary, showing each command letter and
verb with its parameters and a short description of what it does.
Optional arguments are enclosed in square brackets.

File: gdbm.info, Node: gdbmexport, Next: Error codes, Prev: testgdbm, Up: Top

17 Export a database into a portable format.
********************************************

The `gdbmexport' utility converts the database into a portable "flat
format". Files in this format can be used to populate databases using
the `gdbm_import' function (*note gdbm_import: Flat files.) or the `i'
command of `testgdbm' utility (*note testgdbm import::). In many cases
files in this format are suitable for sending over the network to
populate the database on another machine. The only exception to this
are databases whose records contain non-ASCII data (e.g. C structures,
integers etc.). For such databases you will be better off by writing a
specialized utility to convert them to an architecture-independent
format.

If `gdbmexport' is linked with `libgdbm' version 1.8.3, it can be
used to convert databases from old to new format.

The utility takes two mandatory arguments: the name of the database
file to convert and the output file name, e.g.:

$ gdbmexport junk.gdbm junk.flat

In addition two options are understood:

`-h'
Display short usage summary and exit.

`-v'
Display program version and licensing information, and exit.

File: gdbm.info, Node: Error codes, Next: Variables, Prev: gdbmexport, Up: Top

19 Error codes
**************

This chapter summarizes the error codes which can be set by the
functions in `gdbm' library.

GDBM_NO_ERROR
No error occurred.

GDBM_MALLOC_ERROR
Memory allocation failed. Not enough memory.

GDBM_BLOCK_SIZE_ERROR
This error is set by the `gdbm_open' function (*note Open::), if
the value of its BLOCK_SIZE argument is incorrect.

GDBM_FILE_OPEN_ERROR
The library was not able to open a disk file. This can be set by
`gdbm_open' (*note Open::), `gdbm_export' and `gdbm_import'
functions (*note Flat files::).

Inspect the value of the system `errno' variable to get more
detailed diagnostics.

GDBM_FILE_WRITE_ERROR
Writing to a disk file failed. This can be set by `gdbm_open'
(*note Open::), `gdbm_export' and `gdbm_import' functions.

Inspect the value of the system `errno' variable to get more
detailed diagnostics.

GDBM_FILE_SEEK_ERROR
Positioning in a disk file failed. This can be set by `gdbm_open'
(*note Open::) function.

Inspect the value of the system `errno' variable to get a more
detailed diagnostics.

GDBM_FILE_READ_ERROR
Reading from a disk file failed. This can be set by `gdbm_open'
(*note Open::), `gdbm_export' and `gdbm_import' functions.

Inspect the value of the system `errno' variable to get a more
detailed diagnostics.

GDBM_BAD_MAGIC_NUMBER
The file given as argument to `gdbm_open' function is not a valid
`gdbm' file: it has a wrong magic number.

GDBM_EMPTY_DATABASE
The file given as argument to `gdbm_open' function is not a valid
`gdbm' file: it has zero length.

GDBM_CANT_BE_READER
This error code is set by the `gdbm_open' function if it is not
able to lock file when called in `GDBM_READER' mode (*note
GDBM_READER: Open.).

GDBM_CANT_BE_WRITER
This error code is set by the `gdbm_open' function if it is not
able to lock file when called in writer mode (*note Open::).

GDBM_READER_CANT_DELETE
Set by the `gdbm_delete' (*note Delete::) if it attempted to
operate on a database that is open in read-only mode (*note
GDBM_READER: Open.).

GDBM_READER_CANT_STORE
Set by the `gdbm_store' (*note Store::) if it attempted to operate
on a database that is open in read-only mode (*note GDBM_READER:
Open.).

GDBM_READER_CANT_REORGANIZE
Set by the `gdbm_reorganize' (*note Reorganization::) if it
attempted to operate on a database that is open in read-only mode
(*note GDBM_READER: Open.).

GDBM_UNKNOWN_UPDATE
Currently unused. Reserved for future uses.

GDBM_ITEM_NOT_FOUND
Requested item was not found. This error is set by `gdbm_delete'
(*note Delete::) and `gdbm_fetch' (*note Fetch::) when the
requested KEY value is not found in the database.

GDBM_REORGANIZE_FAILED
The `gdbm_reorganize' function is not able to create a temporary
database. *Note Reorganization::.

GDBM_CANNOT_REPLACE
Cannot replace existing item. This error is set by the
`gdbm_store' if the requested KEY value is found in the database
and the FLAG parameter is not `GDBM_REPLACE'. *Note Store::, for
a detailed discussion.

GDBM_ILLEGAL_DATA
Either KEY or CONTENT parameter was wrong in a call to to
`gdbm_store' (*note Store::).

GDBM_OPT_ALREADY_SET
Requested option can be set only once and was already set. This
error is returned by the `gdbm_setopt' function. *Note
GDBM_CACHESIZE: Options.

GDBM_OPT_ILLEGAL
The OPTION argument is not valid or the VALUE argument points to
an invalid value in a call to `gdbm_setopt' function. *Note
Options::.

GDBM_BYTE_SWAPPED
The `gdbm_open' function (*note Open::) attempts to open a
database which is created on a machine with different byte
ordering.

GDBM_BAD_FILE_OFFSET
The `gdbm_open' function (*note Open::) sets this error code if
the file it tries to open has a wrong magic number.

GDBM_BAD_OPEN_FLAGS
Set by the `gdbm_export' function if supplied an invalid FLAGS
argument. *Note Flat files::.

GDBM_FILE_STAT_ERROR
Getting information about a disk file failed. The system `errno'
will give more details about the error.

This error can be set by the following functions: `gdbm_open',
`gdbm_reorganize'.

GDBM_FILE_EOF
End of file was encountered where more data was expected to be
present. This error can occur when fetching data from the database
and usually means that the database is truncated or otherwise
corrupted.

This error can be set by any GDBM function that does I/O. Some of
these functions are: `gdbm_delete', `gdbm_exists', `gdbm_fetch',
`gdbm_export', `gdbm_import', `gdbm_reorganize', `gdbm_firstkey',
`gdbm_nextkey', `gdbm_store'.

File: gdbm.info, Node: Variables, Next: Compatibility, Prev: Error codes, Up: Top

18 Useful global variables.
***************************

The following global variables and constants are available:

-- Variable: gdbm_error gdbm_errno
This variable contains error code from the last failed `gdbm'
call. *Note Error codes::, for a list of available error codes and
their descriptions.

Use `gdbm_strerror' (*note Errors::) to convert it to a
descriptive text.

-- Variable: const char * gdbm_errlist[]
This variable is an array of error descriptions, which is used by
`gdbm_strerror' to convert error codes to human-readable text
(*note Errors::). You can access it directly, if you wish so. It
contains `_GDBM_MAX_ERRNO + 1' elements and can be directly
indexed by the error code to obtain a corresponding descriptive
text.

-- Constant: _GDBM_MIN_ERRNO
The minimum error code used by `gdbm'.

-- Constant: _GDBM_MAX_ERRNO
The maximum error code used by `gdbm'.

-- Variable: const char * gdbm_version
A string containing the version information.

-- Variable: int const gdbm_version_number[3]
This variable contains the `gdbm' version numbers:

Index Meaning
---------------------------------------------------------------
0 Major number
1 Minor number
2 Patchlevel number

Additionally, the following constants are defined in the `gdbm.h'
file:

GDBM_VERSION_MAJOR
Major number.

GDBM_VERSION_MINOR
Minor number.

GDBM_VERSION_PATCH
Patchlevel number.

These can be used to verify whether the header file matches the
library.

To compare two split-out version numbers, use the following function:

-- gdbm interface: int gdbm_version_cmp (int const A[3], int const
B[3])
Compare two version numbers. Return `-1' if A is less than B, `1'
if A is greater than B and `0' if they are equal.

Comparison is done from left to right, so that:

a = { 1, 8, 3 };
b = { 1, 8, 3 };
gdbm_version_cmp (a, b) => 0

a = { 1, 8, 3 };
b = { 1, 8, 2 };
gdbm_version_cmp (a, b) => 1

a = { 1, 8, 3 };
b = { 1, 9. 0 };
gdbm_version_cmp (a, b) => -1

File: gdbm.info, Node: Compatibility, Next: Bugs, Prev: Variables, Up: Top

20 Compatibility with standard `dbm' and `ndbm'.
************************************************

`Gdbm' includes a compatibility layer, which provides traditional
`ndbm' and older `dbm' functions. The layer is compiled and installed
if the `--enable-libgdbm-compat' option is used when configuring the
package.

The compatibility layer consists of two header files: `ndbm.h' and
`dbm.h' and the `libgdbm_compat' library.

Older programs using `ndbm' or `dbm' interfaces can use
`libgdbm_compat' without any changes. To link a program with the
compatibility library, add the following two options to the `cc'
invocation: `-lgdbm -lgdbm_compat'. The `-L' option may also be
required, depending on where `gdbm' is installed, e.g.:

cc ... -L/usr/local/lib -lgdbm -lgdbm_compat

Databases created and manipulated by the compatibility interfaces
consist of two different files: `FILE.dir' and `FILE.pag'. This is
required by the POSIX specification and corresponds to the traditional
usage. Note, however, that despite the similarity of the naming
convention, actual data stored in these files has not the same format as
in the databases created by other `dbm' or `ndbm' libraries. In other
words, you cannot access a standard UNIX `dbm' file with GNU `dbm'!

GNU `dbm' files are not `sparse'. You can copy them with the usual
`cp' command and they will not expand in the copying process.

* Menu:

* ndbm:: NDBM interface functions.
* dbm:: DBM interface functions.

File: gdbm.info, Node: ndbm, Next: dbm, Up: Compatibility

20.1 NDBM interface functions.
==============================

The functions below implement the POSIX `ndbm' interface:

-- ndbm: DBM * dbm_open (char *FILE, int FLAGS, int MODE)
Opens a database. The FILE argument is the full name of the
database file to be opened. The function opens two files:
`FILE.pag' and `FILE.dir'. The FLAGS and MODE arguments have the
same meaning as the second and third arguments of `open' (*note
open a file: (open(2))open.), except that a database opened for
write-only access opens the files for read and write access and
the behavior of the `O_APPEND' flag is unspecified.

The function returns a pointer to the `DBM' structure describing
the database. This pointer is used to refer to this database in
all operations described below.

Any error detected will cause a return value of `NULL' and an
appropriate value will be stored in `gdbm_errno' (*note
Variables::).

-- ndbm: void dbm_close (DBM *DBF)
Closes the database. The DBF argument must be a pointer returned
by an earlier call to `dbm_open'.

-- ndbm: datum dbm_fetch (DBM *DBF, datum KEY)
Reads a record from the database with the matching key. The KEY
argument supplies the key that is being looked for.

If no matching record is found, the `dptr' member of the returned
datum is `NULL'. Otherwise, the `dptr' member of the returned
datum points to the memory managed by the compatibility library.
The application should never free it.

-- ndbm: int dbm_store (DBM *DBF, datum KEY, datum CONTENT, int MODE)
Writes a key/value pair to the database. The argument DBF is a
pointer to the `DBM' structure returned from a call to `dbm_open'.
The KEY and CONTENT provide the values for the record key and
content. The MODE argument controls the behavior of `dbm_store'
in case a matching record already exists in the database. It can
have one of the following two values:

`DBM_REPLACE'
Replace existing record with the new one.

`DBM_INSERT'
The existing record is left unchanged, and the function
returns `1'.

If no matching record exists in the database, new record will be
inserted no matter what the value of the MODE is.

-- ndbm: int dbm_delete (DBM *DBF, datum KEY)
Deletes the record with the matching key from the database. If the
function succeeds, `0' is returned. Otherwise, if no matching
record is found or if an error occurs, `-1' is returned.

-- ndbm: datum dbm_firstkey (DBM *DBF)
Initializes iteration over the keys from the database and returns
the first key. Note, that the word `first' does not imply any
specific ordering of the keys.

If there are no records in the database, the `dptr' member of the
returned datum is `NULL'. Otherwise, the `dptr' member of the
returned datum points to the memory managed by the compatibility
library. The application should never free it.

-- ndbm: datum dbm_nextkey (DBM *DBF)
Continues the iteration started by `dbm_firstkey'. Returns the
next key in the database. If the iteration covered all keys in the
database, the `dptr' member of the returned datum is `NULL'.
Otherwise, the `dptr' member of the returned datum points to the
memory managed by the compatibility library. The application
should never free it.

The usual way of iterating over all the records in the database is:

for (key = dbm_firstkey (dbf);
key.ptr;
key = dbm_nextkey (dbf))
{
/* do something with the key */
}

The loop above should not try to delete any records from the
database, otherwise the iteration is not guaranteed to cover all
the keys. *Note Sequential::, for a detailed discussion of this.

-- ndbm: int dbm_error (DBM *DBF)
Returns the error condition of the database: `0' if no errors
occurred so far while manipulating the database, and a non-zero
value otherwise.

-- ndbm: void dbm_clearerr (DBM *DBF)
Clears the error condition of the database.

-- ndbm: int dbm_dirfno (DBM *DBF)
Returns the file descriptor of the `dir' file of the database. It
is guaranteed to be different from the descriptor returned by the
`dbm_pagfno' function (see below).

The application can lock this descriptor to serialize accesses to
the database.

-- ndbm: int dbm_pagfno (DBM *DBF)
Returns the file descriptor of the `pag' file of the database.
See also `dbm_dirfno'.

-- ndbm: int dbm_rdonly (DBM *DBF)
Returns `1' if the database DBF is open in a read-only mode and
`0' otherwise.

File: gdbm.info, Node: dbm, Prev: ndbm, Up: Compatibility

20.2 DBM interface functions.
=============================

The functions below are provided for compatibility with the old UNIX
`DBM' interface. Only one database at a time can be manipulated using
them.

-- dbm: int dbminit (char *FILE)
Opens a database. The FILE argument is the full name of the
database file to be opened. The function opens two files:
`FILE.pag' and `FILE.dir'. If any of them does not exist, the
function fails. It never attempts to create the files.

The database is opened in the read-write mode, if its disk
permissions permit.

The application must ensure that the functions described below in
this section are called only after a successful call to `dbminit'.

-- dbm: int dbmclose (void)
Closes the database opened by an earlier call to `dbminit'.

-- dbm: datum fetch (datum KEY)
Reads a record from the database with the matching key. The KEY
argument supplies the key that is being looked for.

-- dbm: int store (datum KEY, datum CONTENT)
Stores the key/value pair in the database. If a record with the
matching key already exists, its content will be replaced with the
new one.

Returns `0' on success and `-1' on error.

-- dbm: int delete (datum KEY)
Deletes a record with the matching key.

If the function succeeds, `0' is returned. Otherwise, if no
matching record is found or if an error occurs, `-1' is returned.

-- dbm: datum firstkey (void)
Initializes iteration over the keys from the database and returns
the first key. Note, that the word `first' does not imply any
specific ordering of the keys.

-- dbm: datum nextkey (datum KEY)
Continues the iteration started by a call to `firstkey'. Returns
the next key in the database. If the iteration covered all keys
in the database, the `dptr' member of the returned datum is `NULL'.
Otherwise, the `dptr' member of the returned datum points to the
memory managed by the compatibility library. The application
should never free it.

File: gdbm.info, Node: Bugs, Next: Resources, Prev: Compatibility, Up: Top

21 Problems and bugs.
*********************

If you have problems with GNU `dbm' or think you've found a bug, please
report it. Before reporting a bug, make sure you've actually found a
real bug. Carefully reread the documentation and see if it really says
you can do what you're trying to do. If it's not clear whether you
should be able to do something or not, report that too; it's a bug in
the documentation!

Before reporting a bug or trying to fix it yourself, try to isolate
it to the smallest possible input file that reproduces the problem.
Then send us the input file and the exact results `gdbm' gave you. Also
say what you expected to occur; this will help us decide whether the
problem was really in the documentation.

Once you've got a precise problem, send e-mail to <bug-gdbm AT gnu.org>.

Please include the version number of GNU `dbm' you are using. You
can get this information by printing the variable `gdbm_version' (*note
Variables::).

Non-bug suggestions are always welcome as well. If you have
questions about things that are unclear in the documentation or are
just obscure features, please report them too.

You may contact the authors and maintainers by e-mail:
<phil AT cs.edu>, <downsj AT downsj.com>, <gray AT gnu.ua>

File: gdbm.info, Node: Resources, Next: GNU Free Documentation License, Prev: Bugs, Up: Top

22 Additional resources
***********************

For the latest updates and pointers to additional resources, visit
`http://www.gnu.org/software/gdbm'.

In particular, a copy of `gdbm' documentation in various formats is
available online at `http://www.gnu.org/software/gdbm/manual'.

Latest versions of `gdbm' can be downloaded from anonymous FTP:
`ftp://ftp.gnu.org/gnu/gdbm', or via HTTP from
`http://ftp.gnu.org/gnu/gdbm', or from any GNU mirror worldwide. See
`http://www.gnu.org/order/ftp.html', for a list of mirrors.

To track `gdbm' development, visit
`http://puszcza.gnu.org.ua/projects/gdbm'.

File: gdbm.info, Node: GNU Free Documentation License, Next: Index, Prev: Resources, Up: Top

Appendix A GNU Free Documentation License
*****************************************

Version 1.3, 3 November 2008

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or
noncommercially. Secondarily, this License preserves for the
author and publisher a way to get credit for their work, while not
being considered responsible for modifications made by others.

This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.
It complements the GNU General Public License, which is a copyleft
license designed for free software.

We have designed this License in order to use it for manuals for
free software, because free software needs free documentation: a
free program should come with manuals providing the same freedoms
that the software does. But this License is not limited to
software manuals; it can be used for any textual work, regardless
of subject matter or whether it is published as a printed book.
We recommend this License principally for works whose purpose is
instruction or reference.

1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium,
that contains a notice placed by the copyright holder saying it
can be distributed under the terms of this License. Such a notice
grants a world-wide, royalty-free license, unlimited in duration,
to use that work under the conditions stated herein. The
"Document", below, refers to any such manual or work. Any member
of the public is a licensee, and is addressed as "you". You
accept the license if you copy, modify or distribute the work in a
way requiring permission under copyright law.

A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.

A "Secondary Section" is a named appendix or a front-matter section
of the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall
subject (or to related matters) and contains nothing that could
fall directly within that overall subject. (Thus, if the Document
is in part a textbook of mathematics, a Secondary Section may not
explain any mathematics.) The relationship could be a matter of
historical connection with the subject or with related matters, or
of legal, commercial, philosophical, ethical or political position
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The "Invariant Sections" are certain Secondary Sections whose
titles are designated, as being those of Invariant Sections, in
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The Document may contain zero Invariant Sections. If the Document
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The "Cover Texts" are certain short passages of text that are
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Front-Cover Text may be at most 5 words, and a Back-Cover Text may
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A "Transparent" copy of the Document means a machine-readable copy,
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Examples of suitable formats for Transparent copies include plain
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XML for which the DTD and/or processing tools are not generally
available, and the machine-generated HTML, PostScript or PDF
produced by some word processors for output purposes only.

The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the
material this License requires to appear in the title page. For
works in formats which do not have any title page as such, "Title
Page" means the text near the most prominent appearance of the
work's title, preceding the beginning of the body of the text.

The "publisher" means any person or entity that distributes copies
of the Document to the public.

A section "Entitled XYZ" means a named subunit of the Document
whose title either is precisely XYZ or contains XYZ in parentheses
following text that translates XYZ in another language. (Here XYZ
stands for a specific section name mentioned below, such as
"Acknowledgements", "Dedications", "Endorsements", or "History".)
To "Preserve the Title" of such a section when you modify the
Document means that it remains a section "Entitled XYZ" according
to this definition.

The Document may include Warranty Disclaimers next to the notice
which states that this License applies to the Document. These
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this License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and
has no effect on the meaning of this License.

2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License
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You may also lend copies, under the same conditions stated above,
and you may publicly display copies.

3. COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly
have printed covers) of the Document, numbering more than 100, and
the Document's license notice requires Cover Texts, you must
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these Cover Texts: Front-Cover Texts on the front cover, and
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If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
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If you publish or distribute Opaque copies of the Document
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state in or with each Opaque copy a computer-network location from
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latter option, you must take reasonably prudent steps, when you
begin distribution of Opaque copies in quantity, to ensure that
this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you
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It is requested, but not required, that you contact the authors of
the Document well before redistributing any large number of
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4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document
under the conditions of sections 2 and 3 above, provided that you
release the Modified Version under precisely this License, with
the Modified Version filling the role of the Document, thus
licensing distribution and modification of the Modified Version to
whoever possesses a copy of it. In addition, you must do these
things in the Modified Version:

A. Use in the Title Page (and on the covers, if any) a title
distinct from that of the Document, and from those of
previous versions (which should, if there were any, be listed
in the History section of the Document). You may use the
same title as a previous version if the original publisher of
that version gives permission.

B. List on the Title Page, as authors, one or more persons or
entities responsible for authorship of the modifications in
the Modified Version, together with at least five of the
principal authors of the Document (all of its principal
authors, if it has fewer than five), unless they release you
from this requirement.

C. State on the Title page the name of the publisher of the
Modified Version, as the publisher.

D. Preserve all the copyright notices of the Document.

E. Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.

F. Include, immediately after the copyright notices, a license
notice giving the public permission to use the Modified
Version under the terms of this License, in the form shown in
the Addendum below.

G. Preserve in that license notice the full lists of Invariant
Sections and required Cover Texts given in the Document's
license notice.

H. Include an unaltered copy of this License.

I. Preserve the section Entitled "History", Preserve its Title,
and add to it an item stating at least the title, year, new
authors, and publisher of the Modified Version as given on
the Title Page. If there is no section Entitled "History" in
the Document, create one stating the title, year, authors,
and publisher of the Document as given on its Title Page,
then add an item describing the Modified Version as stated in
the previous sentence.

J. Preserve the network location, if any, given in the Document
for public access to a Transparent copy of the Document, and
likewise the network locations given in the Document for
previous versions it was based on. These may be placed in
the "History" section. You may omit a network location for a
work that was published at least four years before the
Document itself, or if the original publisher of the version
it refers to gives permission.

K. For any section Entitled "Acknowledgements" or "Dedications",
Preserve the Title of the section, and preserve in the
section all the substance and tone of each of the contributor
acknowledgements and/or dedications given therein.

L. Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section
titles.

M. Delete any section Entitled "Endorsements". Such a section
may not be included in the Modified Version.

N. Do not retitle any existing section to be Entitled
"Endorsements" or to conflict in title with any Invariant
Section.

O. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no
material copied from the Document, you may at your option
designate some or all of these sections as invariant. To do this,
add their titles to the list of Invariant Sections in the Modified
Version's license notice. These titles must be distinct from any
other section titles.

You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text
has been approved by an organization as the authoritative
definition of a standard.

You may add a passage of up to five words as a Front-Cover Text,
and a passage of up to 25 words as a Back-Cover Text, to the end
of the list of Cover Texts in the Modified Version. Only one
passage of Front-Cover Text and one of Back-Cover Text may be
added by (or through arrangements made by) any one entity. If the
Document already includes a cover text for the same cover,
previously added by you or by arrangement made by the same entity
you are acting on behalf of, you may not add another; but you may
replace the old one, on explicit permission from the previous
publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this
License give permission to use their names for publicity for or to
assert or imply endorsement of any Modified Version.

5. COMBINING DOCUMENTS

You may combine the Document with other documents released under
this License, under the terms defined in section 4 above for
modified versions, provided that you include in the combination
all of the Invariant Sections of all of the original documents,
unmodified, and list them all as Invariant Sections of your
combined work in its license notice, and that you preserve all
their Warranty Disclaimers.

The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name
but different contents, make the title of each such section unique
by adding at the end of it, in parentheses, the name of the
original author or publisher of that section if known, or else a
unique number. Make the same adjustment to the section titles in
the list of Invariant Sections in the license notice of the
combined work.

In the combination, you must combine any sections Entitled
"History" in the various original documents, forming one section
Entitled "History"; likewise combine any sections Entitled
"Acknowledgements", and any sections Entitled "Dedications". You
must delete all sections Entitled "Endorsements."

6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other
documents released under this License, and replace the individual
copies of this License in the various documents with a single copy
that is included in the collection, provided that you follow the
rules of this License for verbatim copying of each of the
documents in all other respects.

You may extract a single document from such a collection, and
distribute it individually under this License, provided you insert
a copy of this License into the extracted document, and follow
this License in all other respects regarding verbatim copying of
that document.

7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other
separate and independent documents or works, in or on a volume of
a storage or distribution medium, is called an "aggregate" if the
copyright resulting from the compilation is not used to limit the
legal rights of the compilation's users beyond what the individual
works permit. When the Document is included in an aggregate, this
License does not apply to the other works in the aggregate which
are not themselves derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half
of the entire aggregate, the Document's Cover Texts may be placed
on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic
form. Otherwise they must appear on printed covers that bracket
the whole aggregate.

8. TRANSLATION

Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section
4. Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also
include the original English version of this License and the
original versions of those notices and disclaimers. In case of a
disagreement between the translation and the original version of
this License or a notice or disclaimer, the original version will
prevail.

If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to
Preserve its Title (section 1) will typically require changing the
actual title.

9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense, or distribute it is void,
and will automatically terminate your rights under this License.

However, if you cease all violation of this License, then your
license from a particular copyright holder is reinstated (a)
provisionally, unless and until the copyright holder explicitly
and finally terminates your license, and (b) permanently, if the
copyright holder fails to notify you of the violation by some
reasonable means prior to 60 days after the cessation.

Moreover, your license from a particular copyright holder is
reinstated permanently if the copyright holder notifies you of the
violation by some reasonable means, this is the first time you have
received notice of violation of this License (for any work) from
that copyright holder, and you cure the violation prior to 30 days
after your receipt of the notice.

Termination of your rights under this section does not terminate
the licenses of parties who have received copies or rights from
you under this License. If your rights have been terminated and
not permanently reinstated, receipt of a copy of some or all of
the same material does not give you any rights to use it.

10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of
the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
`http://www.gnu.org/copyleft/'.

Each version of the License is given a distinguishing version
number. If the Document specifies that a particular numbered
version of this License "or any later version" applies to it, you
have the option of following the terms and conditions either of
that specified version or of any later version that has been
published (not as a draft) by the Free Software Foundation. If
the Document does not specify a version number of this License,
you may choose any version ever published (not as a draft) by the
Free Software Foundation. If the Document specifies that a proxy
can decide which future versions of this License can be used, that
proxy's public statement of acceptance of a version permanently
authorizes you to choose that version for the Document.

11. RELICENSING

"Massive Multiauthor Collaboration Site" (or "MMC Site") means any
World Wide Web server that publishes copyrightable works and also
provides prominent facilities for anybody to edit those works. A
public wiki that anybody can edit is an example of such a server.
A "Massive Multiauthor Collaboration" (or "MMC") contained in the
site means any set of copyrightable works thus published on the MMC
site.

"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
license published by Creative Commons Corporation, a not-for-profit
corporation with a principal place of business in San Francisco,
California, as well as future copyleft versions of that license
published by that same organization.

"Incorporate" means to publish or republish a Document, in whole or
in part, as part of another Document.

An MMC is "eligible for relicensing" if it is licensed under this
License, and if all works that were first published under this
License somewhere other than this MMC, and subsequently
incorporated in whole or in part into the MMC, (1) had no cover
texts or invariant sections, and (2) were thus incorporated prior
to November 1, 2008.

The operator of an MMC Site may republish an MMC contained in the
site under CC-BY-SA on the same site at any time before August 1,
2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents
====================================================

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:

Copyright (C) YEAR YOUR NAME.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ``GNU
Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts." line with this:

with the Invariant Sections being LIST THEIR TITLES, with
the Front-Cover Texts being LIST, and with the Back-Cover Texts
being LIST.

If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License, to
permit their use in free software.

File: gdbm.info, Node: Index, Prev: GNU Free Documentation License, Up: Top

Index
*****

[index]
* Menu:

* -g, testgdbm option: testgdbm. (line 9)
* -n, testgdbm option: testgdbm. (line 19)
* -r, testgdbm option: testgdbm. (line 16)
* 1: shell. (line 118)
* <: shell. (line 125)
* ?: shell. (line 200)
* _GDBM_MAX_ERRNO: Variables. (line 28)
* _GDBM_MIN_ERRNO: Variables. (line 25)
* A: shell. (line 143)
* a: shell. (line 142)
* avail: shell. (line 141)
* B: shell. (line 148)
* b: shell. (line 147)
* bucket: shell. (line 146)
* C: shell. (line 153)
* c: shell. (line 63)
* ca: shell. (line 172)
* cache: shell. (line 171)
* close-on-exec: Open. (line 48)
* closing database: Close. (line 6)
* co: shell. (line 62)
* command line options, testgdbm: invocation. (line 6)
* compatibility layer: Compatibility. (line 6)
* count: shell. (line 61)
* creating a database, testgdbm: testgdbm. (line 19)
* cu: shell. (line 152)
* current: shell. (line 151)
* D: shell. (line 158)
* d: shell. (line 68)
* da: shell. (line 191)
* data-zero: shell. (line 190)
* database options: Options. (line 6)
* database reorganization: Reorganization. (line 6)
* database synchronization: Sync. (line 6)
* database, closing: Close. (line 6)
* database, opening or creating: Open. (line 6)
* DBM functions: dbm. (line 6)
* dbm.h: Compatibility. (line 11)
* dbm_clearerr: ndbm. (line 98)
* dbm_close: ndbm. (line 26)
* dbm_delete: ndbm. (line 57)
* dbm_dirfno: ndbm. (line 101)
* dbm_error: ndbm. (line 93)
* dbm_fetch: ndbm. (line 30)
* dbm_firstkey: ndbm. (line 62)
* DBM_INSERT: ndbm. (line 49)
* dbm_nextkey: ndbm. (line 72)
* dbm_open: ndbm. (line 9)
* dbm_pagfno: ndbm. (line 109)
* dbm_rdonly: ndbm. (line 113)
* DBM_REPLACE: ndbm. (line 46)
* dbm_store: ndbm. (line 39)
* dbmclose: dbm. (line 23)
* dbminit: dbm. (line 11)
* de: shell. (line 67)
* default database, testgdbm: testgdbm. (line 9)
* delete <1>: dbm. (line 42)
* delete: shell. (line 66)
* deleting records: Delete. (line 6)
* deletion in iteration loops: Sequential. (line 56)
* di: shell. (line 157)
* dir: shell. (line 156)
* dir file: Compatibility. (line 22)
* e: shell. (line 72)
* error codes: Error codes. (line 6)
* error strings: Errors. (line 6)
* export <1>: shell. (line 71)
* export: Flat files. (line 6)
* F: shell. (line 163)
* f: shell. (line 82)
* fe: shell. (line 81)
* fetch <1>: dbm. (line 26)
* fetch: shell. (line 80)
* fetching records: Fetch. (line 6)
* fi: shell. (line 117)
* first: shell. (line 116)
* firstkey: dbm. (line 48)
* Flat file format: Flat files. (line 6)
* GDBM_BAD_FILE_OFFSET: Error codes. (line 117)
* GDBM_BAD_MAGIC_NUMBER: Error codes. (line 48)
* GDBM_BAD_OPEN_FLAGS: Error codes. (line 121)
* GDBM_BLOCK_SIZE_ERROR: Error codes. (line 15)
* GDBM_BYTE_SWAPPED: Error codes. (line 112)
* GDBM_CACHESIZE: Options. (line 30)
* GDBM_CANNOT_REPLACE: Error codes. (line 92)
* GDBM_CANT_BE_READER: Error codes. (line 56)
* GDBM_CANT_BE_WRITER: Error codes. (line 61)
* GDBM_CENTFREE: Options. (line 78)
* GDBM_CLOEXEC: Open. (line 48)
* gdbm_close: Close. (line 10)
* GDBM_COALESCEBLKS: Options. (line 92)
* gdbm_delete: Delete. (line 9)
* gdbm_delete and sequential access: Sequential. (line 56)
* GDBM_EMPTY_DATABASE: Error codes. (line 52)
* gdbm_errlist: Variables. (line 17)
* gdbm_errno: Variables. (line 9)
* gdbm_exists: Fetch. (line 37)
* gdbm_export: Flat files. (line 25)
* GDBM_FASTMODE: Options. (line 52)
* gdbm_fdesc: Locking. (line 14)
* gdbm_fetch: Fetch. (line 7)
* GDBM_FILE_EOF: Error codes. (line 132)
* GDBM_FILE_OPEN_ERROR: Error codes. (line 19)
* GDBM_FILE_READ_ERROR: Error codes. (line 41)
* GDBM_FILE_SEEK_ERROR: Error codes. (line 34)
* GDBM_FILE_STAT_ERROR: Error codes. (line 125)
* GDBM_FILE_WRITE_ERROR: Error codes. (line 27)
* gdbm_firstkey: Sequential. (line 14)
* GDBM_GETCACHESIZE: Options. (line 40)
* GDBM_GETCOALESCEBLKS: Options. (line 104)
* GDBM_GETDBNAME: Options. (line 127)
* GDBM_GETFLAGS: Options. (line 44)
* GDBM_GETMAXMAPSIZE: Options. (line 114)
* GDBM_GETMMAP: Options. (line 123)
* GDBM_GETSYNCMODE: Options. (line 74)
* GDBM_ILLEGAL_DATA: Error codes. (line 98)
* gdbm_import: Flat files. (line 46)
* GDBM_INSERT: Store. (line 23)
* GDBM_ITEM_NOT_FOUND: Error codes. (line 83)
* GDBM_MALLOC_ERROR: Error codes. (line 12)
* GDBM_NEWDB <1>: Flat files. (line 35)
* GDBM_NEWDB: Open. (line 28)
* gdbm_nextkey: Sequential. (line 24)
* GDBM_NO_ERROR: Error codes. (line 9)
* GDBM_NOLOCK <1>: Locking. (line 6)
* GDBM_NOLOCK: Open. (line 40)
* GDBM_NOMMAP: Open. (line 40)
* gdbm_open: Open. (line 9)
* GDBM_OPT_ALREADY_SET: Error codes. (line 102)
* GDBM_OPT_ILLEGAL: Error codes. (line 107)
* GDBM_READER: Open. (line 28)
* GDBM_READER_CANT_DELETE: Error codes. (line 65)
* GDBM_READER_CANT_REORGANIZE: Error codes. (line 75)
* GDBM_READER_CANT_STORE: Error codes. (line 70)
* gdbm_reorganize: Reorganization. (line 9)
* GDBM_REORGANIZE_FAILED: Error codes. (line 88)
* GDBM_REPLACE: Store. (line 23)
* GDBM_SETCACHESIZE: Options. (line 30)
* GDBM_SETCENTFREE: Options. (line 78)
* GDBM_SETCOALESCEBLKS: Options. (line 92)
* GDBM_SETMAXMAPSIZE: Options. (line 108)
* GDBM_SETMMAP: Options. (line 118)
* gdbm_setopt: Options. (line 11)
* GDBM_SETSYNCMODE: Options. (line 61)
* gdbm_store: Store. (line 8)
* gdbm_strerror: Errors. (line 9)
* gdbm_sync: Sync. (line 15)
* GDBM_SYNC <1>: Sync. (line 6)
* GDBM_SYNC: Open. (line 40)
* GDBM_SYNCMODE: Options. (line 61)
* GDBM_UNKNOWN_UPDATE: Error codes. (line 80)
* gdbm_version: Variables. (line 31)
* gdbm_version_cmp: Variables. (line 61)
* GDBM_VERSION_MAJOR: Variables. (line 45)
* GDBM_VERSION_MINOR: Variables. (line 48)
* gdbm_version_number: Variables. (line 34)
* GDBM_VERSION_PATCH: Variables. (line 51)
* GDBM_WRCREAT <1>: Flat files. (line 35)
* GDBM_WRCREAT: Open. (line 28)
* GDBM_WRITER: Open. (line 28)
* gdbmexport: gdbmexport. (line 6)
* H: shell. (line 168)
* ha: shell. (line 167)
* hash: shell. (line 166)
* hea: shell. (line 162)
* header: shell. (line 161)
* hel: shell. (line 199)
* help: shell. (line 198)
* i: shell. (line 86)
* import <1>: shell. (line 85)
* import: Flat files. (line 6)
* interactive mode, testgdbm: shell. (line 6)
* iterating over records: Sequential. (line 6)
* iteration and gdbm_delete: Sequential. (line 56)
* iteration loop: Sequential. (line 36)
* iteration loop, using NDBM: ndbm. (line 79)
* junk.gdbm: testgdbm. (line 9)
* K: shell. (line 173)
* k: shell. (line 136)
* key-zero: shell. (line 135)
* l: shell. (line 92)
* libgdbm_compat: Compatibility. (line 11)
* list: shell. (line 91)
* locking: Locking. (line 6)
* looking up records: Fetch. (line 6)
* n: shell. (line 96)
* NDBM functions: ndbm. (line 6)
* ndbm.h: Compatibility. (line 11)
* next: shell. (line 95)
* nextkey: dbm. (line 58)
* opening the database: Open. (line 6)
* options, database: Options. (line 6)
* pag file: Compatibility. (line 22)
* PAGER: shell. (line 45)
* pager, testgdbm: shell. (line 45)
* q: shell. (line 107)
* quit: shell. (line 106)
* r: shell. (line 132)
* rea: shell. (line 124)
* read: shell. (line 123)
* read-only mode, testgdbm: testgdbm. (line 16)
* record, deleting: Delete. (line 6)
* record, fetching: Fetch. (line 6)
* records, iterating over: Sequential. (line 6)
* records, storing: Store. (line 6)
* records, testing existence: Fetch. (line 34)
* reo: shell. (line 131)
* reorganization, database: Reorganization. (line 6)
* reorganize: shell. (line 130)
* S: shell. (line 178)
* s: shell. (line 112)
* sequential access: Sequential. (line 6)
* sequential access, using NDBM: ndbm. (line 79)
* sta: shell. (line 177)
* status: shell. (line 176)
* sto: shell. (line 111)
* store <1>: dbm. (line 35)
* store: shell. (line 110)
* storing records: Store. (line 6)
* synchronization, database: Sync. (line 6)
* testgdbm: testgdbm. (line 6)
* v: shell. (line 187)
* version: shell. (line 186)
* version number: Variables. (line 30)
* Z: shell. (line 192)
* z: shell. (line 137)

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