Ubuntu Manpage: cdb - Constant DataBase manipulation tool

NAME

       cdb - Constant DataBase manipulation tool

SYNOPSYS

       cdb -q [-m] [-n num] dbname key
       cdb -d [-m] [dbname|-]
       cdb -l [-m] [dbname|-]
       cdb -s [dbname|-]
       cdb -c [-m] [-t tmpname|-] [-p perms] [-weru0] dbname [infile...]

DESCRIPTION

cdb used to query, dump, list, analyze or create CDB (Constant DataBase) files. Format of cdb described
in cdb(5) manpage. This manual page corresponds to version 0.78 of tinycdb package.

Query
cdb -q finds given key in a given dbname cdb file, and writes associated value to standard output if
found (and exits with zero), or exits with non-zero if not found. dbname must be seekable file, and
stdin can not be used as input. By default, cdb will print all records found. Options recognized in
query mode:

-nnum causes cdb to find and write a record with a given number num starting with 1 — when there are
many records with a given key.

-m newline will be added after every value printed. By default, multiple values will be written
without any delimiter.

Dump/List
cdb -d dumps contents, and cdb -l lists keys of cdbfile (or standard input if not specified) to standard
output, in format controlled by presence of -m option. See subsection "Formats" below. Output from cdb
-d can be used as an input for cdb -c.

Create
Cdb database created in two stages: temporary database is created, and after it is complete, it gets
atomically renamed to permanent place. This avoids requirements for locking between readers and writers
(or creaters). cdb -c will attempt to create cdb in file tmpname (or dbname with ".tmp" appended if no
-t option given) and then rename it to dbname. It will read supplied infiles (or standard input if none
specified). Options recognized in create mode:

-t tmpname
use given tmpname as temporary file. Defaults to dbname.tmp (i.e. with output file with .tmp
added). Note tmpname must be in the same filesystem as output file, as cdb uses rename(2) to
finalize the database creation procedure. If tmpname is a single dash (-), no temp file will be
created, database will be built in-place. This mode is useful when the final renaming is done by
the caller.

-p perms
permissions for the newly created file (usually an octal number, like 0644). By default the
permissions are 0666 (with current process umask applied). If this option is specified, current
umask value has no effect.

-w warn about duplicate keys.

-e abort on duplicate keys (implies -w).

-r replace existing key with new one in case of duplicate. This may require database file rewrite to
remove old records, and can be slow.

-0 zero-fill existing records when duplicate records are added. This is faster than -r, but leaves
extra zeros in the database file in case of duplicates.

-u do not add duplicate records.

-m interpret input as a sequence of lines, one record per line, with value separated from a key by
space or tab characters, instead of native cdb format (see "Input/Output Format" below).

Note that using any option that requires duplicate checking will slow creation process significantly,
especially for large databases.

Statistics
cdb -s will analyze dbfile and print summary to standard output. Statistics include: total number of
rows in a file, minimum, average and maximum key and value lengths, hash tables (max 256) and entries
used, number of hash collisions (that is, more than one key point to the same hash table entry), minimum,
average and maximum hash table size (of non-empty tables), and number of keys that sits at 10 different
distances from it's calculated hash table index — keys in distance 0 requires only one hash table lookup,
1 — two and so on; more keys at greater distance means slower database search.

Input/Output Format
By default, cdb expects (for create operation) or writes (for dump/list) native cdb format data. Cdb
native format is a sequence of records in a form:
+klen,vlen:key->val\n
where "+", ",", ":", "-", ">" and "\n" (newline) are literal characters, klen and vlen are length of key
and value as decimal numbers, and key and val are key and value themselves. Series of records terminated
by an empty line. This is the only format where key and value may contain any character including
newline, zero (\0) and so on.

When -l option requested (list keys mode), cdb will produce slightly modified output in a form:
+klen:key\n
(note vlen and val are omitted, together with surrounding delimiters).

If -m option is given, cdb will expect or produce one line for every record (newline is a record
delimiter), and every line should contain optional whitespace, key, whitespace and value up to end of
line. Lines started with hash character (#) and empty lines are ignored. This is the same format as
mkmap(1) utility expects.

OPTIONS SUMMARY

       Here is a short summary of all options accepted by cdb utility:

       -0     zero-fill duplicate records in create (-c) mode.

       -c     create mode.

       -d     dump mode.

       -e     abort (error) on duplicate key in create (-c) mode.

       -h     print short help and exit.

       -l     list mode.

       -m     input  or output is in "map" format, not in native cdb format.  In query mode, add a newline after
              every value written.

       -nnum  find and print numth record in query (-q) mode.

       -q     query mode.

       -r     replace duplicate keys in create (-c) mode.

       -s     statistics mode.

       -t tempfile
              specify temporary file when creating (-c) cdb file (use single dash (-) as tempfile to stop  using
              temp file).

       -u     do not insert duplicate keys (unique) in create (-c) mode.

       -w     warn about duplicate keys in create (-c) mode.

AUTHOR

       The  tinycdb  package  written  by Michael Tokarev <mjt@corpit.ru>, based on ideas and shares file format
       with original cdb library by Dan Bernstein.

LICENCE