GDBMTOOL(1) GDBM User Reference GDBMTOOL(1)
NAME
gdbmtool - examine and modify a GDBM database
SYNOPSIS
gdbmtool [-lmNnqrs] [-b SIZE] [-c SIZE] [-f FILE] [--block-size=SIZE]
[--cache-size=SIZE] [--file FILE] [--newdb] [--no-lock] [--no-mmap]
[--norc] [--quiet] [--read-only] [--synchronize] [DBFILE] [COMMAND [;
COMMAND...]]
gdbmtool [-Vh] [--help] [--usage] [--version]
DESCRIPTION
The gdbmtool utility allows you to view and modify an existing GDBM
database or to create a new one.
The DBFILE argument supplies the name of the database to open. If not
supplied, the default name junk.gdbm is used instead. If the named
database does not exist, it will be created. An existing database can
be cleared (i.e. all records removed from it) using the --newdb option
(see below).
Unless the -N (--norc) option is given, after startup gdbmtool looks
for file named .gdbmtoolrc first in the current working directory, and,
if not found there, in the home directory of the user who started the
program. If found, this file is read and interpreted as a list of
gdbmtool commands.
Then gdbmtool starts a loop, in which it reads commands from the stan-
dard input, executes them and prints the results on the standard out-
put. If the standard input is attached to a console, the program runs
in interactive mode.
The program terminates when the quit command is given, or end-of-file
is detected on its standard input.
Commands can also be specified in the command line, after the DBFILE
argument. In this case, they will be interpreted without attempting to
read more commands from the standard input.
If several commands are supplied, they must be separated by semicolons
(properly escaped or quoted, in order to prevent them from being inter-
preted by the shell).
A gdbmtool command consists of a command verb, optionally followed by
one or more arguments, separated by any amount of white space. A com-
mand verb can be entered either in full or in an abbreviated form, as
long as that abbreviation does not match any other verb.
Any sequence of non-whitespace characters appearing after the command
verb forms an argument. If the argument contains whitespace or
unprintable characters it must be enclosed in double quotes. Within
double quotes the usual escape sequences are understood, as shown in
the table below:
Escape Expansion
\a Audible bell character (ASCII 7)
\b Backspace character (ASCII 8)
\f Form-feed character (ASCII 12)
\n Newline character (ASCII 10)
\r Carriage return character (ASCII 13)
\t Horizontal tabulation character (ASCII 9)
\v Vertical tabulation character (ASCII 11)
\\ Single slash
In addition, a backslash immediately followed by the end-of-line char-
acter effectively removes that character, allowing to split long argu-
ments over several input lines.
OPTIONS
-b, --block-size=SIZE
Set block size.
-c, --cache-size=SIZE
Set cache size.
-f, --file=FILE
Read commands from FILE, instead of from the standard input.
-l, --no-lock
Disable file locking.
-m, --no-mmap
Do not use mmap(2).
-n, --newdb
Create the database, truncating it if it already exists.
-q, --quiet
Don't print initial banner.
-r, --read-only
Open database in read-only mode.
-s, --synchronize
Synchronize to disk after each write.
-h, --help
Print a short usage summary.
--usage
Print a list of available options.
-V, --version
Print program version
SHELL COMMANDS
avail Print the avail list.
bucket NUM
Print the bucket number NUM and set is as the current one.
cache Print the bucket cache.
close Close the currently open database.
count Print the number of entries in the database.
current
Print the current bucket.
delete KEY
Delete record with the given KEY.
dir Print hash directory.
export FILE-NAME [truncate] [binary|ascii]
Export the database to the flat file FILE-NAME. This is equiva-
lent to gdbm_dump(1).
This command will not overwrite an existing file, unless the
truncate parameter is also given. Another optional parameter
determines the type of the dump (*note Flat files::). By
default, ASCII dump will be created.
fetch KEY
Fetch and display the record with the given KEY.
first Fetch and display the first record in the database. Subsequent
records can be fetched using the next command (see below).
hash KEY
Compute and display the hash value for the given KEY.
header Print file header.
help or ?
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.
history
Shows the command history list with line numbers. This command
is available only if the program was compiled with GNU Readline.
history COUNT.
Shows COUNT latest commands from the command history.
history N COUNT.
Shows COUNT commands from the command history starting with Nth
command.
import FILE-NAME [replace] [nometa]
Import data from a flat dump file FILE-NAME. If the replace
argument is given, any records with the same keys as the already
existing ones will replace them. The nometa argument turns off
restoring meta-information from the dump file.
list List the contents of the database.
next [KEY]
Sequential access: fetch and display the next record. If the
KEY is given, the record following the one with this key will be
fetched.
open FILE
Open the database file FILE. If successful, any previously open
database is closed. Otherwise, if the operation fails, the cur-
rently opened database remains unchanged.
This command takes additional information from the variables
open, lock, mmap, and sync. See the section VARIABLES, for a
detailed description of these.
quit Close the database and quit the utility.
reorganize
Reorganize the database.
set [VAR=VALUE...]
Without arguments, lists variables and their values. If argu-
ments are specified, sets variables. Boolean variables can be
set by specifying variable name, optionally prefixed with no, to
set it to false.
source FILE
Read commands from the given FILE.
status Print current program status.
store KEY DATA
Store the DATA with the given KEY in the database. If the KEY
already exists, its data will be replaced.
unset VARIABLE...
Unsets listed variables.
version
Print the version of gdbm.
DATA DEFINITIONS
The define statement provides a mechanism for defining key or content
structures. It is similar to the C struct declaration:
define key|content { defnlist }
The defnlist is a comma-separated list of member declarations. Within
defnlist the newline character looses its special meaning as the com-
mand terminator, so each declaration can appear on a separate line and
arbitrary number of comments can be inserted to document the defini-
tion.
Each declaration has one of the following formats
type name
type name [N]
where type is a data type and name is the member name. The second for-
mat defines the member name as an array of N elements of type.
The supported types are:
type meaning
char single byte (signed)
short signed short integer
ushort unsigned short integer
int signed integer
unsigned unsigned integer
uint ditto
long signed long integer
ulong unsigned long integer
llong signed long long integer
ullong unsigned long long integer
float a floating point number
double double-precision floating point number
string array of characters (see the NOTE below)
stringz null-terminated string of characters
The following alignment declarations can be used within defnlist:
offset N
The next member begins at offset N.
pad N Add N bytes of padding to the previous member.
For example:
define content {
int status,
pad 8,
char id[3],
stringz name
}
To define data consisting of a single data member, the following sim-
plified construct can be used:
define key|content type
where type is one of the types discussed above.
NOTE: The string type can reasonably be used only if it is the last or
the only member of the data structure. That's because it provides no
information about the number of elements in the array, so it is inter-
preted to contain all bytes up to the end of the datum.
VARIABLES
confirm, boolean
Whether to ask for confirmation before certain destructive oper-
ations, such as truncating the existing database. Default is
true.
ps1, string
Primary prompt string. Its value can contain conversion speci-
fiers, consisting of the % character followed by another charac-
ter. These specifiers are expanded in the resulting prompt as
follows:
Sequence Expansion
%f name of the db file
%p program name
%P package name (gdbm)
%_ horizontal space (ASCII 32)
%v program version
%% %
The default prompt is %p>%_.
ps2, string
Secondary prompt. See ps1 for a description of its value. This
prompt is displayed before reading the second and subsequent
lines of a multi-line command.
The default value is %_>%_.
delim1, string
A string used to delimit fields of a structured datum on output
(see the section DATA DEFINITIONS).
Default is , (a comma). This variable cannot be unset.
delim2, string
A string used to delimit array items when printing a structured
datum.
Default is , (a comma). This variable cannot be unset.
pager, string
The name and command line of the pager program to pipe output
to. This program is used in interactive mode when the estimated
number of output lines is greater then the number of lines on
your screen.
The default value is inherited from the environment variable
PAGER. Unsetting this variable disables paging.
quiet, boolean
Whether to display welcome banner at startup. This variable
should be set in a startup script file.
The following variables control how the database is opened:
cachesize, numeric
Sets the cache size. By default this variable is not set.
blocksize, numeric
Sets the block size. Unset by default.
open, string
Open mode. The following values are allowed:
newdb Truncate the database if it exists or create a new one.
Open it in read-write mode.
wrcreat or rw
Open the database in read-write mode. Create it if it
does not exist. This is the default.
reader or readonly
Open the database in read-only mode. Signal an error if
it does not exist.
filemode, octal
Sets the file mode for newly created database files. Default is
0644.
lock, boolean
Lock the database. This is the default.
mmap, boolean
Use memory mapping. This is the default.
coalesce, boolean
When set, this option causes adjacent free blocks to be merged
which allows for more efficient memory management at the expense
of a certain increase in CPU usage.
centfree, boolean
Enables central free block pool. This causes all free blocks of
space to be placed in the global pool, thereby speeding up the
allocation of data space.
SEE ALSO
gdbm_dump(1), gdbm_load(1), gdbm(3).
REPORTING BUGS
Report bugs to <bug-gdbm AT gnu.org>.
COPYRIGHT
Copyright (C) 2013-2018 Free Software Foundation, Inc
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>;
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
GDBM June 27, 2018 GDBMTOOL(1)
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