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.::gnugo(6) User Contributed Perl Documentation .::gnugo(6)


gnugo - The GNU program to play the game of Go


gnugo [--boardsize <num>] [--color <color>] [--handicap <num>] [--komi <num>] [--quiet] [-v, --version] [-h, --help] [--help debug] [--copyright] [--mode <mode>] [--replay <color>] [-l, --infile <filename>] [-L, --until <move>] [-o, --outfile <filename>] [--printsgf <filename>] [-D, --depth <num>] [-B, --backfill_depth <num>] [--score [estimate⎪finish⎪aftermath] ] [-a, --allpats] [-T, --printboard] [-d, --debug <level>] [-w, --worms] [-m, --moyo <level>] [-b, --benchmark num] [-t, --trace] [-r, --seed num]


GNU Go plays a game of Go against the user. It has many other features: it can play against itself or another program, analyse and score a recorded game. GNU Go is compliant with Go modem protocol, load and save game in the Smart Game format.

GNU Go default is a simple alpha-numeric board display, but you can use a client such as CGoban.

The game of Go

Go is a game of strategy between two players usually played on a 19x19 grid called goban. The two players put black and white stones on the goban to enclose territory. Go was invented about 4000 years ago in ancient China. Other names for this game are (Chinese) Wei Chi, (Korean) Baduk and (Ing) Goe.

Playing a game in ASCII mode

To start a game with default options, just invoke "gnugo". The board will be drawn at your terminal using ASCII letters. In this mode, you can get help on available commands by the h key. To play as Black with 4 stones handicap, with a 0.5 komi, recording the game in the file record.sgf:

 gnugo --color black --handicap 4 --komi 0.5 -o record.sgf

Playing a game with CGoban

CGoban is a general purpose client program by Bill Shubert for playing Go. It runs under X Window System with a beautiful resizeable graphic display. To use GNU Go under X Window System, obtain the most recent version of CGoban from Bill Shubert's web site

Start CGoban. When the CGoban Control panel comes up, select `Go Modem.' You will get the Go Modem Protocol Setup. Choose one (or both) of the players to be ``Program,'' and fill out the box to the path to gnugo. After clicking OK, you get the Game Setup window. Choose ``Rules Set'' to be Japanese (otherwise handicaps won't work). Set the board size and handicap if you want. Click OK and you are ready to go.

In the Go Modem Protocol Setup window, when you specify the path to GNU Go, you can give it command line options, such as --quiet to suppress most messages. Since the Go Modem Protocol preempts standard I/O, other messages are sent to stderr, even if they are not error messages. These will appear in the terminal from which you started CGoban.

Scoring system

The game stops when both players pass. GNU Go will attempt to compute and report the score to you. It may occasionally make mistakes due to wrong evaluation of the status of a group. You can check the score as follows. In ASCII mode, at the end of the game, stones believed dead are marked in lower case letters, and you have the option of toggling their status before counting. Using CGoban, you may use CGoban's counting facility to count the game using either Japanese or Chinese rules.

Viewing a stored game

gnugo -l filename.sgf --mode ascii

loads filename.sgf and lets you navigate through the game by using the commands forward, back, goto and last. It is not possible to navigate through variations in ascii mode. You may also use CGoban to view stored games. CGoban can navigate variations.


The files in the doc directory contain detailed documentation about debugging options and internal program structure. Other documentation may be found in comments throughout the source code.

Go Modem Protocol

The Go Modem Protocol is a standard interface between Go programs and graphical display.

The Go Modem Protocol was developed by Bruce Wilcox with input from David Fotland, Anders Kierulf and others. Any Go program *should* use this protocol since it is standard. Since CGoban supports this protocol, the user interface for any Go program can be done entirely through CGoban. Using the Go Modem Protocol, you can play with another computer running a different program (even on a different operating system) using a modem, a serial cable or over the internet if the other program also supports the protocol. You can also communicate with the Go servers using CGoban.

Smart Game Format

Games (with comments, variations and other features) can be stored in the Smart Game Format (SGF). This format originated in Anders Kierulf's program Smart Go. Martin Muller and Arno Hollosi developed the current standard, which may be found at

GNU Go supports the Smart Game Format.


Main options

--mode mode

force the playing mode (ascii', gtp or gmp). Default is ASCII. If no terminal is detected GMP (Go Modem Protocol) will be assumed.

--replay color

replay the game generating moves for color, where color is white, black, or both. (requires -l)


Don't print copyright and other informational messages.

-l, --infile file

Load the SGF file (to score or analyze a recorded game).

-L, --until move

Stop loading just before move is played (e.g. 154 or L10).

-o, --outfile file

Save the played game to file in SGF format.

Game Options:

--boardsize num

Set the board size to use (1-19). Default is 19, other common formats are 13 and 9.

--color color

Choose your color (black or white). Black plays first, White gets the komi compensation.

--handicap num

Set the number of handicap stones.

--komi num

Set the komi (points given to white player to compensate advantage of the first move, usually 5.5 or 0.5). Default is 5.5.

Informative Output:

-v, --version

Display the version of GNU Go.

-h, --help

Display help message.

--help debug

Display help about debugging options.


Display copyright notice.

Debugging and advanced options:

-T, --printboard

Show board each move.

--level num

Level of play. (default 10; smaller=faster, weaker).

-b, --benchmark num

Benchmarking mode - can be used with -l.

-t, --trace

Verbose tracing (use twice or more to trace reading).

-r, --seed num

Set random number seed.

--score [estimate⎪finish⎪aftermath]

Count or estimate territory of the input file. Usage:

gnugo --score estimate -l filename

Loads the SGF file and estimates the score by measuring the influence. Use with -L if you want the estimate somewhere else than at the end of the file.

gnugo --score finish -l filename

Loads the SGF file and gnugo continues to play by itself up to the very end. Then the winner is determined by counting the territory.

gnugo --score aftermath -l filename

Similar to --score finish except that a more accurate but slower algorithm is used to determine the final status of the groups.

If the option -o outputfilename is provided, the results will also be written as comment at the end of the output file.

--printsgf outfile

Load SGF file, output final position (requires -l).


If you find a bug, please send the SGF output file to together with a description of the bug.

3.7.7 3rd Berkeley Distribution