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pgn-extract 16.0-1
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          pgn-extract: a Portable Game Notation (PGN) manipulator

Overview

This file documents a program to extract selected games from a PGN format
data file. There are several ways to specify the criteria on which to
extract: textual move sequences, the position reached after a sequence of
moves, information in the tag fields, and material balance in the ending.
Full ANSI C source for the program is available under the terms of the GNU
General Public License. The program includes a semantic analyser which will
report errors in game scores and it is also able to detect duplicate games
found in one or more of its input files.

The range of input move formats accepted is fairly wide and includes
recognition of lower-case piece letters for English and upper-case piece
letters for Dutch and German. The default output is in English Standard
Algebraic Notation (SAN), although there is some support for output in
different notations.

Extracted games may be written out either including or excluding comments,
NAGs, and variations. Games may be given ECO classifications derived from
the accompanying file eco.pgn, or a customised version provided by the
user.

Index

   * Flag summary
   * Usage and Arguments (-f)
   * Input Format
   * Output Files (-o, -a)
   * Variations:
        o Positional Variations (-x)
        o Textual Variations (-v)
   * Textual Variation Permutations (-P)
   * Duplicate Games (-d and -D, plus -Z)
   * Suppression of Unique Games (-U)
   * Matching on Tag Criteria (-t)
   * Date and Elo Matches with -t
   * Tag Criteria on the Command Line (-T)
   * Date Matches with -T
   * Argument Descriptions in a File (-A)
   * Outputing Games not matched (-n)
   * Check Files for Duplicates (-c)
   * Setting bounds on the number of moves in a game (-b)
   * ECO Classification (-e)
   * Separate Output Files (-#, -E)
   * Soundex Matching (-S)
   * Output Line Length (-w)
   * Output Format and Language (-W)
   * Forsyth-Edwards Notation (FEN) Descriptions (-F)
   * Material Matches (-z)
   * The Seven Tag Roster (-7)
   * User-defined Tag Roster Ordering (-R)
   * Mailing List
   * Limitations
   * The Files
   * Portability
   * Acknowledgements
   * License
   * A History of Changes to the Original Release

Flag summary

There follows a brief summary of the different flags taken by pgn-extract,
such as is produced by the -h flag. You are strongly advised to read the
remainder of this file, however, before attempting to use extract in
earnest.

     Flags:
   * -7 - output only the seven tag roster for each game. Other tags (apart
     from FEN and possibly ECO/Opening/Variation) are discarded (See -e).
   * -aoutputfile - the file to which extracted games are to be appended.
     See -o flag for overwriting an existing file.
   * -Aargsfile - read the program's arguments from argsfile.
   * -b[elu]num - restricted bounds on the number of moves in a game.
        o lnum set a lower bound of 'num' moves,
        o unum set an upper bound of 'num' moves,
        o otherwise num (or enum) means equal-to 'num' moves.
   * -cfile[.pgn] - Use file as a list of check files for duplicates.
   * -C - don't include comments in the output. Ordinarily these are
     retained.
   * -dduplicatefile - the file to which duplicate extracted games are to
     be written.
   * -D - don't output duplicate extracted game scores.
   * -eECO_file - perform ECO classification of games. The optional
     ECO_file should contain a PGN format list of ECO lines Default is to
     use eco.pgn from the current directory.
   * -E[123 etc.] - split output into separate files according to ECO.
        o E1 : Produce files from ECO letter, A.pgn, B.pgn, ...
        o E2 : Produce files from ECO letter and first digit, A0.pgn, ...
        o E3 : Produce files from full ECO code, A00.pgn, A01.pgn, ...
        o Further digits may be used to produce non-standard further
          refined division of games.
     All files are opened in append mode.
   * -ffile_list - file_list contains the list of PGN files to be searched
     - one per line.
   * -F - output a FEN string comment of the final game position.
   * -h - print an abbreviated list of help.
   * -h1 - print further help.
   * -? - print an abbreviated list of help.
   * -llogfile - Create a new logfile for the diagnostics rather than using
     stderr.
   * -Llogfile - Append all diagnostics to logfile.
   * -noutputfile - Write all valid games not otherwise output to
     outputfile.
   * -N - don't include NAGs in the output. Ordinarily these are retained.
   * -ooutputfile - the file to which extracted games are to be written.
     Any existing contents of the file are lost (see -a flag).
   * -P - don't match permutations of the textual variations (-v).
   * -r - report any errors but don't extract.
   * -Rtagorder - Use the tag ordering specified in the file tagorder.
   * -s - silent mode don't report each game as it is extracted.
   * -S - Use a simple soundex algorithm for tag matches. If used, this
     option must precede the -t or -T options.
   * -ttagfile - file of player, date, or result, extraction criteria.
   * -Tcriterion - player, date, or result, extraction criteria.
   * -U - don't output games that only occur once. (Use with -d to identify
     duplicates in multiple files.)
   * -vvariations - the file variations contains the textual lines of
     interest.
   * -V - don't include variations in the output. Ordinarily these are
     retained.
   * -wwidth - set width as an approximate line width for output.
   * -W - don't rewrite the moves into Standard Algebraic Notation.
   * -W[cm|epd|halg|lalg|elalg|san] - specify the output format to use.
        o Default (i.e., without this flag) is SAN.
        o -W (without anything following) selects the input format.
        o -Wcm is a legacy option that wrote ChessMaster format. I don't
          know if the output produced is still valid.
        o -Wepd is EPD format.
        o -Whalg is hyphenated long algebraic.
        o -Wlalg is long algebraic
        o -Welalg[PNBRQK] is enhanced long algebraic. Use the characters PNBRQK
	  for language specific output, e.g: -WelalgBSLTDK for German.
        o -Wsan[PNBRQK] Use the characters PNBRQK for language specific
          output, e.g: -WsanBSLTDK for German.
   * -xvariations - the file variations contains the lines resulting in
     positions of interest.
   * -zendings - the file endings contains the end positions of interest.
   * -Z - use the file virtual.tmp as an external hash table for
     duplicates. Use when MallocOrDie messages occur with big datasets.
   * -#num - output num games per file, to files named 1.pgn, 2.pgn, etc.

Error messages and verbose reporting is done to the standard error output
unless the -l/-L flag is used.

Usage and Arguments (-f)

Extract takes an arbitrary number of game scores as input and outputs zero
or more of these games, typically in English Standard Algebraic Notation
(SAN). Which of the input games are output, and the style of the output,
depend upon the particular set of command line flags passed to pgn-extract.
The general form for calling pgn-extract is as follows:

    pgn-extract [flags] [input-game-files]

In its simplest form, calling pgn-extract with no arguments will cause it
to read games from its standard input, check them and reproduce those
without errors in SAN notation on its standard output.

Normally, the input files from which games are to be extracted are listed
on the command line:

    pgn-extract file1.pgn [file2.pgn ...]

An alternative to listing the game files on the command line is to list
their names, one per line, in a file which is then given after the -f flag:

    pgn-extract -ffile_list

In order to save the output in a file rather than standard output, use
either -o or -a to indicate the output file name, for instance:

    pgn-extract -oall.pgn file1.pgn file2.pgn file3.pgn

While pgn-extract can be used simply to check and reformat all the input
games, it is more usual to use it to select subsets of the input games.
Several different criteria are available on which to extract: move
variations, information in the tag fields, and material balance in the
ending, for instance. All of these criteria are described in detail below.

Input Format

This program's principle aim is to be able to read PGN files and output
games of interest. It follows that the input should look reasonably like
PGN to start with. This means that it doesn't cope well with files that
contain news article or mail headers, for instance, although it does make
an attempt to skip text that is obviously not game related between games.
Having said that, it does not require the move text be in Standard
Algebraic Notation (SAN). It will accept quite a few common formats
including:

   * Algebraic
   * Long Algebraic
   * various commonly-used intervening characters, such as : - x
   * Dutch and German upper case piece letters. (Support for Russian piece
     letters is in prototype.)
   * lower-case English piece characters (except that it will always prefer
     'b' to mean a pawn move rather than a Bishop move).

It does not require that there be any move numbers or PGN headers preceding
a game, as long as the move text is terminated by a valid result
designation: *, 1-0, 0-1, 1/2-1/2 (1/2 is also accepted). This makes the
program reasonably suitable for entering raw game text and having it
reformatted in proper SAN with a full set of headers.

Output Files (-o, -a)

In order to output all matched games to a single new file, the -o flag is
used:

    pgn-extract -onew.pgn file1.pgn file2.pgn

This has the effect of creating new.pgn from the contents of file1.pgn and
file2.pgn. The games in both source files are checked and rewritten, if
necessary, into SAN. Any previous contents of new.pgn will be lost with the
-o flag. In order to avoid this and append to an existing file, use the -a
flag:

    pgn-extract -anew.pgn file1.pgn file2.pgn

Note that there should be no space between either -o or -a and the output
file name.

Variations (-v and -x)

There are two distinct ways to specify variations of interest; positional
variations (the -x flag) and textual variations (the -v flag). The major
difference between the two is that positional variations specify a complete
move sequence whose end position is the primary point of interest, whereas
textual variations allow incomplete and fuzzy move sequence matches on the
text of a game to select games. Whilst it is possible to use both flags
together, this would be unusual as a game must match with both to be
extracted.

Positional Variations (-x)

The variations in which you are interested should be placed in a file whose
name is supplied with the -x flag. For instance:

    pgn-extract -xvars

where each variation is listed on a single line in the file vars (the
filename is immaterial). The following set of moves:

    e4 c5 Nf3 d6 d4 cxd4 Nxd4 Nf6 Nc3 a6

indicates that you wish to pick up all games reaching the Najdorf variation
position of the Sicilian Defence. Games reaching the end position of this
sequence are selected regardless of the route that was taken to reach it.
This allows various transpositional sequences to be specified by quoting
just one line to reach the required point. Therefore, games employing the
following move order will be picked up by quoting the line above.

    e4 c5 Nc3 d6 Nge2 Nf6 d4 cxd4 Nxd4 a6

A position is considered to match a required variation if it generates the
same board hash value. In the interests of reasonable efficiency, no
attempt is made to actually examine the state of the board. There is,
therefore, the potential for false hits but in my usage of pgn-extract I
have not found this to be a problem.

With this option, games are only searched to a depth approximately equal to
the length of the longest positional variation, in order to make processing
of large data sets faster than with a search of the whole game.

A comment line may be placed in a variation file by using a '%' as the
first character of the line. Move numbers are optional within the list of
moves.

From version 14.0 onwards, an alternative form of positional match is
available using a FEN description of the desired position. See the
description of the -t flag for how to specify a FEN position, and the -F
flag for a simple way to generate a FEN description from a game score.

Textual Variations (-v)

With this option, the matching is purely textual in nature, in contrast to
the -x flag. The -v flag works by string matching on the input text of
moves, so there is no facility for picking up transpositions automatically.
The variations in which you are interested should be placed in a file whose
name is supplied with the -v flag. For instance:

    pgn-extract -vvars

Each variation should be listed on a single line in the file vars (the
filename is immaterial). The move sequence:

    e4 c5 Nf3 d6 d4 cxd4 Nxd4 Nf6 Nc3 a6

indicates that you wish to pick up all games following the normal move
order of the Najdorf variation of the Sicilian Defence, and

    d4 Nf6 c4 e6 Nc3 Bb4

that you are interested in Nimzo-Indian games. The order in which the moves
are played by either White or Black is immaterial. All combinations are
tried, so the ordering:

    c4 e6 Nc3 Bb4 d4 Nf6

will produce the same set of matches as the previous ordering of the
Nimzo-Indian moves (see the -P flag for how to prevent this).

A comment line may be placed in a variation file by using a '%' as the
first character of the line. Move numbers are optional within the list of
moves.

As transpositions are not picked up automatically with this flag, if you
also wanted to recognise the following as a Najdorf, you would have to add
this line to the variations file in addition to that given above:

    e4 c5 Nc3 d6 Nge2 Nf6 d4 cxd4 Nxd4 a6

However, because of the way in which the matching is done, it is possible
to specify slight alternatives on the way in which individual moves are
written. Notational alternatives for a single move are just written
separated from each other with a non-move character. This variation
specifies both the shorter and longer ways of writing the captures in a
Najdorf:

    e4 c5 Nf3 d6 d4 cxd4|cd Nxd4|Nd4 Nf6 Nc3 a6

However, given the variety of possible ways of writing various moves in
non-SAN format, e.g.

    cxd4|cd|c5d4|c5-d4

variation lists can get quite messy and I believe that this approach is
best avoided by ensuring that the input is proper SAN and only using SAN
notation in the variations file. In this way, the alternative-separator can
then be used purely for indicating genuine alternative moves at that point,
e.g.

    e4 c5 Nf3 d6 d4|d3

An important point when listing moves is that check and mate indicators
should be included where appropriate, otherwise moves incorporating these
characters in games to be searched will fail to match.

There is little point in using the -v flag in preference to the -x flag if
you are only interested in finding games that reach a particular position.
The real use for -v is when you wish to pick up games in a more general
way. For instance, the character '*' may be used in place of any move to
indicate that you don't care what was played at that point. So the
following:

    * b6

means that you are interested in all games in which Black replied 1 ... b6
regardless of White's first move. The sequence:

    d4 * c4 * Nc3 *

will pick up Nimzo-Indian, Grunfeld, King's Indian, etc. defences. This
notation is not possible with positional variations.

In addition, the character '!' may be used in front of any move to indicate
that you wish to disallow particular moves from matching at this point. For
instance, if you want to find Sicilian games where White did not reply with
Nf3 at move 2 you would specify:

    e4 c5 !Nf3

If you wished to disallow 2.Ne2 as well then

    e4 c5 !Nf3|Ne2

does the job. (Adding parentheses makes no difference as the '!' is applied
to all of the following move string.)

Care should be taken combining '!', '*' and variation permutations (see the
-P flag). Disallowed moves take precedence over '*' moves. If a single
disallowed move is found in a game within the length of the variation, that
game is excluded. This was the most sensible interpretation that I could
find to place on this usage.

Textual Variation Permutations (-P)

Normally, all permutations of a textual variation (see the -t flag) are
tried against the moves of a game. This cuts down on the number of separate
transpositional orderings that it is necessary to list, at the cost of
slower matching of each game. If the following were used to look for
Nimzo-Indian games:

    d4 Nf6 c4 e6 Nf6 Nc3 Bb4

a side-effect would be that it will also pick up games which start as:

    1. c4 Nf6 2. Nc3 e6 3. d4 Bb4

for instance. The -P flag requests that textual variations are matched
against the moves of the game strictly in the order in which they are
listed, without trying different orders. So, if you want to find only those
games that follow a particular move order, use this flag to suppress
permutations.

Duplicate Games (-d and -D, plus -Z)

If either the -d or -D flag is used, pgn-extract attempts to recognise
duplicate extracted games. Using the -d flag indicates that you wish copies
of the duplicate games to be written to the indicated file:

    pgn-extract -ddupes.pgn -ounique.pgn file.pgn

will extract from file.pgn the unique set of games into unique.pgn and the
duplicates (i.e., the second and subsequent copies of a game) to dupes.pgn.
A comment identifying in which file a duplicate was found precedes the
first duplicate found in that file and each duplicate game has a prefix
comment indicating the file in which the first version was found.

With the -D flag duplicate games are suppressed from the output. These two
flags are mutually exclusive, therefore.

Duplicates are identified by comparing a hash value for the board of the
end positions of extracted games and an additional cumulative hash value
generated from the move sequence. If these both values match then games are
considered to be duplicates. This is not guaranteed to be exact but it
gives a good approximation.

You should note that games are only considered to be duplicates on the
basis of the moves played. It may be that a game considered to be a
duplicate contains annotations and variations not present in the one found
earlier, so it might be necessary to do some swapping around to obtain
those you really wish to retain. You should, therefore, use the -D flag
with caution if you are trying to reorganise your master collection rather
than selecting out specific games for examination. (See also the -U flag.)

Detecting duplicates requires memory for the storage of a hash table
containing information on each game. No attempt is made to use extended or
expanded memory and so large databases can result in a MallocOrDie error.
If this is the case, try using the -Z flag which forces pgn-extract to
store its hash table externally, in a file called virtual.tmp. Each game
requires 16 bytes of file space. Clearly, if a very large database is being
processed, there is a risk of filling up the available file space if there
is insufficient available.

Suppression of Unique Games (-U)

The -U flag suppresses output of the first occurrence of a particular game.
This is useful when combined with the -d flag as a means of identifying
just those games that are duplicated in a list of multiple files. As the
duplicate games are commented with the file in which they were located, it
then becomes possible to prune a set of files containing common games. For
instance, suppose oldfile.pgn contains a set of games without duplicates,
and you wish to know which games in newfile.pgn already occur in
oldfile.pgn:

    pgn-extract -U -ddupes.pgn oldfile.pgn newfile.pgn

will write to dupes.pgn the duplicate games so that you can go through
newfile.pgn and remove them. Of course, if you simply want to hold the
combined set of games in a single file you would use something like:

    pgn-extract -D -onewset.pgn oldfile.pgn newfile.pgn

See Duplicate Games for dealing with MallocOrDie errors.

Matching on Tag Criteria (-t)

There are two ways to specify that you wish to use information in the tag
fields as extraction criteria: the -t flag and the -T flag. The -t flag
takes a file name argument and is the preferred method because of its ease
of use and greater flexibility:

    pgn-extract -ttags games.pgn

where tags is an arbitrary file name. In the file are listed tag name and
value pairs corresponding to the extraction criteria you wish to use. Each
line of this file should be of the form:

    PGN-Tag-name Tag-string

for instance:

    White "Tal"

(note the need to include double quotes around the tag value). This
requests that only those games where Tal had the White pieces are to be
considered for extraction. If you wish to limit the year in which those
games were played you might list:

    White "Tal"
    Date "1962"

Multiple pairs with the same tag name are or-ed together so:

    % Find games in the period 1960-1962.
    Date "1960"
    Date "1961"
    Date "1962"

will select all games from the three listed years. Note that comments may
be included in the tag file.

In general, tags names that differ are and-ed together, so:

    White "Tal"
    Black "Fischer"
    Date "1962"
    Result "1-0"

selects only those games that Tal won with the White pieces against Fischer
in 1962.

It is important to note that:

    White "Tal"
    Black "Tal"

does not find all games played by Tal, but only those that he played
against himself. In order to overcome this, I have introduced a non-PGN tag
that should only be used in the extraction criteria file:

    Player "Tal"
    Date "1962"

finds all games from 1962 in which Tal had either the White pieces or the
Black. In effect, the White and Black player lists are or-ed together
rather than and-ed using this pseudo-tag.

Prefix matching on tag values is done so that a criterion should be a
prefix of the complete Tag string. Thus,

    Player "Karpov"

would match:

    [White "Karpov"]
    [White "Karpov, A"]
    [White "Karpov, An"]
    [White "Karpov, Alexander"]

but not

    [White "Anatoli Karpov"]

See the -S flag for a soundex facility with tag matching.

All tag criteria except ECO classification are checked before the moves of
the game in the interests of efficiency (tag checking is relatively fast
whereas positional checking of the game is not). Only once the game has
been processed is it checked to see whether an ECO tag match has been
requested. The consequence of this is that using the -e flag in combination
with ECO tag criteria you can search for games in particular ECO lines
without an ECO tag having been present in the input form.

From version 14.0 onwards, use of a FEN tag with the -t flag has a special
meaning. Rather than using this to match FEN tags in the header of a game,
a FEN description is used to indicate a search for a positional match
(similar to use of the -x flag). If a FEN description is provided with the
-t flag, the indicated position is searched for in each game processed, and
only those games that reach the indicated position are output. A FEN
tag-pair for the starting position would be described by:

    FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"

The position after the two moves e4 c5 would be:

    FEN "rnbqkbnr/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/RNBQKBNR w KQkq c6 0 2"

See details of the -F flag for a simple way to generate a FEN description
from a game score.

Date and Elo Matches with -t

From a -t tag file, more complex matching of dates and Elo values may be
performed by placing an operator between the tag name and the tag string to
be matched:

    Date < "1962"

would only match games played before 1962. Only the year value participates
in the matching process, as this is done using integer values rather than
strings.

    WhiteElo >= "2500"

only matches games where White is a strong player. Probably of more general
use is another pseudo-tag that I have introduced purely for this purpose:
Elo.

    Elo >= "2500"

matches games in which either player has an Elo tag matching that
relationship. The operators allowed are >, >=, <, <=, =, and <> (not equal
to).

Tag Criteria on the Command Line (-T)

An alternative to the -t flag is the -T flag, for use where command line
arguments are more convenient - perhaps where pgn-extract is being invoked
from another program. The tag coverage is not as extensive as with a tag
file, and the syntax is rather cumbersome. It is used as follows: after the
-T comes a single letter from the limited set [bdprw] to select string
prefixes of the tag fields of a game. For instance:

   * -TwPlayer - Extract games where Player has the White pieces.
   * -TbPlayer - Extract games where Player has the Black pieces.
   * -TpPlayer - Extract games where Player has either colour.
   * -TdDate - Extract games played on Date.
   * -TrResult - Extract games with result Result.
   * -TaAnnotator - Extract games Annotated by Annotator.
   * -TeEco - Extract games with ECO designation Eco.

For example,

    pgn-extract -TwTal -TbFischer file.pgn

would extract games from file.pgn in which Tal had the White pieces and
Fischer the Black.

Criteria of the same tag type are or-ed together, so

    pgn-extract -Tr1-0 -Tr0-1 file.pgn

extracts only decisive games.

Criteria of different tag types are and-ed together so

    pgn-extract -TwTal -Td1962 -Tr1-0 file.pgn

would extract only those games in which Tal played with the White pieces in
1962 and won.

The ECO classification (see the -e flag) is performed before attempting to
match an ECO tag, so:

    pgn-extract -TeA01 -e file.pgn

will perform ECO classification on the input file and extract games with
ECO classification A01 (Nimzo-Larsen attack), for instance.

Argument Descriptions in a File (-A)

It can be inconvenient to repeatedly type long argument lists on the
command line. The -A flag makes it possible to list arguments in a file,
rather than on a command line. Each argument line within the file must be
immediately preceded by a ':' (colon) character. Consider selecting games
by Tal from a file caro.pgn and writing them to talgames.pgn. Using command
line arguments, this would have the following form:

    pgn-extract -TpTal -otalgames.pgn caro.pgn

We can do the same job placing the argument list in the file args:

    % Select games by Tal.
    :-TpTal
    % Where to output the matched games.
    :-otalgames.pgn

and the same selection made with:

    pgn-extract -Aargs caro.pgn

Note that comments may be included using a '%' character.

Each argument should be listed on its own line, and all the arguments are
available in this way. The PGN source files may also be listed in the
argument file. They must be listed one per line, with a preceding colon
character. So an alternative for the above would be:

    % Select games by Tal.
    :-TpTal
    % Where to output the matched games.
    :-otalgames.pgn
    % The game files to be read.
    :caro.pgn

and the command invoked as simply:

    pgn-extract -Aargs

The -t, -v, -x, -z, and -R flags have slightly special treatment in an
argument file. Where the tags, variations, positions, endings and/or roster
ordering are to be read from files of those names, say, then the format of
these arguments in the argument file might be as you would expect:

    :-ttags
    :-vvariations
    :-xpositions
    :-zendings
    :-Rroster

However, within an argument file, the file names are optional, and it is
also possible to list further data for these flags on lines immediately
following. For instance, an alternative to:

    :-TpTal

we could say:

    :-t
    Player "Tal"

Notice that no colon should be present on the lines following the flag
line. In the following example, we select games won by Tal as White
reaching a particular position in the Caro Kann:

    :-t
    White "Tal"
    Result "1-0"
    :-otalwins.pgn
    :-x
    e4 c6 d4 d5 exd5 cxd5
    % Which game files to process.
    :caro.pgn

The arguments file may, itself, also contain -A arguments. This should make
it possible to build up hierarchies of game selection criteria if desired.
However, beware that there is no check for circularities in the
dependencies.

Outputting Games not Matched (-n)

The -n flag will cause all valid games not output via other criteria to be
saved in a given file. The purpose of this is to make it easier to
reorganise files in different ways. For instance, if you wish to remove all
of the games played by Tal from one file, you might do:

    pgn-extract -TpTal -otalgames.pgn -nothers.pgn file.pgn

After which, the file others.pgn will contain all of the valid games from
the original file, with the exception of Tal's.

Check Files for Duplicates (-c)

Check files contain games that are to be used in duplicate detection, but
not to form part of the output. If the filename appended to the argument
has a .pgn/.PGN suffix it is assumed to be a single file of games. If it
does not have this suffix then it is assumed to be a file containing a list
of the names of PGN game files, one per line, to be used as check files. A
typical use for this is to select new games of interest from a file that
probably contains games that exist elsewhere. In the following example, we
wish to select Nimzo-Indian games from newfile.pgn that don't already occur
in the master file nimzo.pgn:

    pgn-extract -cnimzo.pgn -vnimzo.var -D -onewnimzo.pgn newfile.pgn

The games in nimzo.pgn act as the source for duplicate detection so
duplicates of these will be suppressed (the -D flag). Only those games from
newfile.pgn which are not in nimzo.pgn will be output to newnimzo.pgn.
Contrast this behaviour with the following, which would create a new master
file of games from the combination of nimzo.pgn and newfile.pgn:

    pgn-extract -vnimzo.var -D -onewnimzo.pgn nimzo.pgn newfile.pgn

Date Matches with -T

A simple form of relational date matching is available from the command
line (-T). A date year may be prefixed with either 'b' or 'a' in order to
match games played either before or after the specified date. This assumes
that the date is stored in the game's date tag string in the normal form:
YYYY.MM.DD

So,

    pgn-extract -Tdb1962 file.pgn

will look for games played before 1962. A much fuller capability is
available in tag files with the -t flag.

Setting bounds on the number of moves in a game (-b)

The -b flag allows you to select games which have a number of moves within
the bounds you set. You can set a lower bound on the number of moves by
using -bl ('l' = lower bound), or an upper limit by using -bu ('u' = upper
bound). Both are followed by the number of moves so

    pgn-extract -bu20 file.pgn

will find brevities of 20 moves or less, whilst

    pgn-extract -bl60 file.pgn

will find games of 60 moves or move. Bounds may be combined so

    pgn-extract -bl30 -bu40 file.pgn

will find games in the range [30..40] moves. If neither 'l' nor 'u' is
used, but just a number following the -b, this means that the number of
moves must exactly match that number. Alternatively, 'e' can be used to
stand for 'equal to'. The following are equivalent and find all games of
exactly 35 moves.

    pgn-extract -b35 file.pgn
    pgn-extract -be35 file.pgn

ECO Classification (-e)

A PGN file of ECO classifications is distributed with this version. I
believe that this was put together by Ewart Shaw, Franz Hemmer and others,
to whom appropriate thanks is due. The -e flag requests pgn-extract to
add/replace ECO classifications in the games it outputs. This is done by
firstly reading a file of ECO lines in PGN format (eco.pgn in the current
directory, by default) and building a table of resulting positions. As the
games are then read they are looked up in the table to find a
classification. The deepest match is found. The supplied file has ECO,
Opening, and Variation tag strings for many lines. If present, pgn-extract
will add/replace these as well as SubVariation tags if available.

An alternative file to the default eco.pgn may be supplied in two ways:
either appending a file name to the -e

    -emy_eco_codes

or by setting the environment variable ECO_FILE to the full path name of
the file. Under DOS this can be done with

    set ECO_FILE=eco-file-path

in the AUTOEXEC.BAT file. Under UNIX csh this can be done with

    setenv ECO_FILE eco-file-path

in the .cshrc, for instance.

Having the ECO data read as plain text on program startup has the obvious
disadvantage that there is a high initial time overhead. On the other hand,
it has the advantage that users may add their own classifications to the
file very easily. It is fairly demanding of memory, so you advised not to
combine this with duplicate detection (-U, -D and -d), which can also
consume a lot of memory with big databases.

Because an ECO tag match with either the -t flag or the -T flag is delayed
until after ECO classification, this makes it relatively easy to select
games with particular ECO codes even if they weren't present in the source
form.

Usage of -e with the Seven Tag Roster flag (-7) results in the ECO tags
(ECO, Opening, Variation, SubVariation) being included in the output games.

Separate Output Files (-#, -E)

The -# and -E flags permit the output to be split into multiple files.
However, be warned that where the input involves a lot of games, these
flags might result in the creation of a large number of output files.

The -# flag takes an unsigned integer argument specifying the maximum
number of games to output to a single file. Successive output files are
numbered 1.pgn, 2.pgn, etc. Any existing contents of these files are always
overwritten on each run of pgn-extract.

       pgn-extract -#250 file.pgn

will check and split file.pgn into separate files of, at most, 250 games
each.

       pgn-extract -#1 file.pgn

will split file.pgn into separate files containing only a single game each.

The -E flag normally takes a numeric argument of value 1, 2, or 3. This is
used to indicate the level of subdivision required based upon the ECO tag
found in a game.

       pgn-extract -E3 file.pgn

will fully subdivide file.pgn into separate files based on the full ECO
code of each game, with names such as B03.pgn, A01.pgn, D45.pgn, etc. If a
game does not contain an ECO tag, or the tag appears to be malformed, it
will be written to a file called, noeco.pgn. All of these files are written
to in append mode, so that existing contents are not lost. However, beware
of using an input file whose name is the same as one that will be written
to by this operation. This could lead to infinite operation.

Level 1 classification uses just the initial letter of the ECO
classification to append to files A.pgn, B.pgn, etc. Level 2 uses the
initial letter and first digit, producing A0.pgn, B3.pgn, etc.

In fact, values greater than 3 may be used to produce separation of even
finer granularity if more than two digits have been used in the
classification of a game.

Soundex Matching (-S)

There is a simple soundex algorithm available that attempts soundex matches
on White, Black, Site, Event, and Annotator tags if the -S flag is used in
combination with either the -t flag or the -T flag. The -S flag should
precede all -t and -T arguments. It should be noted that the soundex
matching does produce false matches.

Output Line Length (-w)

The -w flag allows an approximate line width to be set for output. The
default value is 75 characters. The following request output lines to be
approximately 100 characters wide:

    pgn-extract -w100 file.pgn

Output Format and Language (-W)

By default, pgn-extract rewrites the game score into English Standard
Algebraic Notation (SAN) because it is reasonably flexible about the input
form that it will accept. To prevent it from rewriting the original form of
the moves it reads, use the -W flag.

By itself, -W outputs the moves using the input text.
Using -Wlalg writes the moves in long algebraic form (e.g., e2e4).
Using -Whalg writes them in hyphenated long algebraic (e.g., e2-e4).
Using -Welalg writes the moves in enhanced long algebraic form (e.g., Ne2e4,
e5d6ep). The purpose of enhanced long algebraic form is to reduce the
amount of chess-specific knowledge that a post-procesing program might
need in order to interpret a chess program. For instance, in order to
provide a visualisation.

Output using non-English piece letters is possible using a variation of the
-Wsan flag. This flag may have a six-letter suffix indicating the letters
to be used in representing pawn, knight, bishop, rook, queen and king in
game scores and diagrams. So:

    pgn-extract -WsanPNBRQK ...

would output in the (default) English notation, and

    pgn-extract -WsanBSLTDK ...

would output in German. Note that the letter for a pawn is required because
board positions are sometimes output when an error is detected in a game
score.

-Wepd was introduced in version 15.0 to output in EPD (Extended Position
Description). A game is output as a sequence of EPD descriptions of the
position at the start of the game, and following each move. Each EPD line
contains the FEN board description, the active colour, castling
availability and en passant target square. A c0 comment contains a synopsis
of the player, event, site and date tags from the game's header.

-Wcm is a legacy flag and outputs the moves in what I believe to be (or
used to be) ChessMaster format.

Forsyth-Edwards Notation (FEN) Descriptions (-F)

The -t flag makes it possible to use Forsyth-Edwards Notation (FEN) in the
description of a position to be matched. The -F flag provides a convenience
method for generating a suitable FEN description of an arbitrary position.
The -F flag causes pgn-extract to output a FEN description of the final
position reached in a game, within the text of a comment. For instance,
suppose you were interested in finding games that reach the position after
the following moves.

    d4 Nf6 c4 e6 Nf3 b6 Nc3 Bb7 e3 Bb4 Bd3 O-O O-O Bxc3 bxc3 c5 *

Storing these moves in the file fen.pgn and running

    pgn-extract -F fen.pgn

would generate the score:

    [Event "?"]
    [Site "?"]
    [Date "????.??.??"]
    [Round "?"]
    [White "?"]
    [Black "?"]
    [Result "*"]

    1. d4 Nf6 2. c4 e6 3. Nf3 b6 4. Nc3 Bb7 5. e3 Bb4 6. Bd3 O-O 7. O-O Bxc3 8.
    bxc3 c5
    { "rn1q1rk1/pb1p1ppp/1p2pn2/2p5/2PP4/2PBPN2/P4PPP/R1BQ1RK1/ w - c6 0 9" } *

This FEN string could then be cut and pasted to an argument file and used
with the -t flag to supply matches:

    :-t
    FEN "rn1q1rk1/pb1p1ppp/1p2pn2/2p5/2PP4/2PBPN2/P4PPP/R1BQ1RK1/ w - c6 0 9"

(Note that the FEN string output with -F does not attempt to record the
number of halfmoves since the last pawn move or capture.)

Material Matches (-z)

The -z flag takes a filename of material balances for which you wish to
search in games. The basic structure of the file is one or more lines of
the form

    pieces1 pieces2

Pieces1 and pieces2 are lists of English piece letters for the material for
the two sides that you wish to look for in a game. For instance:

    rp nb

looks for an game in which a lone Rook and Pawn for one side are competing
against a lone Knight and Bishop for the other. The case of the letters is
immaterial, there is no need to include Kings in the description, and the
order of the pieces does not matter. Apart from Kings, if a piece letter is
not listed for a side then then that piece is not present within that
side's material. A match will be tested for from both White and Black's
point of view, so the example above matches the same games as:

    nb rp

Some notation may be added after any piece letter, typically to indicate
something about the number of occurrences of that piece on one side.

The following are valid for each piece:

   * * (zero or more of that piece).
   * + (one or more of that piece).
   * d (exactly d occurrences of that piece, where d is a digit).
   * d+ (d or more occurrences of that piece).
   * d- (d or fewer occurrences of that piece).

So:

    QR2B2N2P8 QR2B2N2P8

is the starting material position, and QR+B*N*P7- represents material in
which we require at least one pawn to be missing from one side and they
should have a Queen and Rook, but we don't care about the minor pieces.

In addition, some extra notation is available to specify material relative
to the opponent's. These are placed after the piece letter to which they
refer.

   * = (the number of these pieces must be the same as the opponent's).
   * # (the number of these pieces must be different the opponent's).
   * > (the number of these pieces more than the opponent has).
   * < (the number of these pieces less than the opponent has).

So,

    R+P+ R=P#

looks for Rook and Pawn games that with an equal number of Rooks but
unbalanced pawns.

In addition > and < may be preceded by a digit:

   * d> (the number of these pieces must be at least d more than the
     opponent's).
   * d< (the number of these pieces must be at least d less than the
     opponent's).

Two more notations, >=, <= may be preceded by an optional digit (the
default is 1). The meaning of this may not be intuitively obvious and, to
an extent, they represent a notational compromise.

   * d>= (the number of these pieces must be exactly d more than the
     opponent's).
   * d<= (the number of these pieces must be exactly d less than the
     opponent's).

In this example, both sides have a pair or Rooks but one has exactly one
pawn more than the other:

    r2p* r=p1>=

Here is an example where one side has sacrificed a Rook and Pawn for Knight
and Bishop and we don't care whether Queens are on or off the board, so
long as they are balanced:

    q*r+n*b*p+ q=r<n>b>p1<

This example represents some of the imprecision that can occur with
matches. The meaning of 'r<' is such that this could match positions in
which one side as 2 Rooks and the other none. This can be corrected with:

    q*r+n*b*p+ q=r1<=n>b>p1<

enforcing strictly one Rook less. We ought also to correct the same problem
with the minor pieces:

    q*r+n*b*p+ q=r1<=n1>=b1>=p1<

In practice, we probably want to allow general matching of minor pieces so
the letter 'L' may be used to stand for a minor piece (Bishop or Knight).
This example represents a similar sacrifice of Rook and Pawn for two minor
pieces.

    q*r+l*p+ q=r1<=l2>=p1<

I would advise against mixing the minor piece letter with Knight and Bishop
letters in the piece set for a single side, however, as I am not convinced
that it will produce exact results.

Position Stability with -z

The piece sets may be preceded by an optional number indicating the
required stability of the position. Normally, if you are looking for a
position with a particular set of material characteristics then you
probably want that position to last for a reasonable number of moves in
order to study its characteristics. The number before the piece sets is how
many half-moves you wish that material balance to last. By default, this
has a value of 2 so that fleeting positions in the middle of pairs of
exchanges do not produce unwanted matches. This example looks for
double-Rook and pawn games that last at least 10 half-moves:

    10 R2P+ R=P*

Text may be added after the piece lists as a form of comment.

A comment line may be placed in a material balance file by using a '%' as
the first character of the line.

The Seven Tag Roster (-7)

This flag discards tag pairs that are not part of the Seven Tag Roster:

    Event, Site, Date, Round, White, Black and Result.

However, if the original game included a FEN tag, this is included in the
output, as the moves will make no sense otherwise. In addition, if the -e
flag has been used for ECO classification, any ECO, Opening, Variation and
SubVariation tags are also output.

User-defined Tag Roster Ordering (-R)

The -R flag makes it possible for to define the order in which tags for a
game are listed in the output. The flag should be immediately followed by
the name of a file that contains a list of tag names, one per line, for
instance:

    pgn-extract -Rroster file.pgn

where roster might contain:

    % Output the tags of the seven tag roster alphabetically.
    Black
    Date
    Event
    Result
    Round
    Site
    White

The '%' character may be used to include comments in the file. Tags not
listed in such a file will appear after the required tags have been output.

Mailing List

If you find the program useful and would like to be put on a mailing list
to receive news of updates or to share suggestions that you think others
might be interested in, then drop me a line at D.J.Barnes@kent.ac.uk

Limitations

The moves, variations, and commentary of each game are held internally and
reformatted when a game is extracted, rather than reproducing the original
text of the game source.

Lower-case 'b' as the first character of a move is taken to be a move of
the b-pawn if one to match the move can be found. Otherwise, Bishop moves
are tried as an alternative. There is no back-up on failure if picking a
valid pawn move was the wrong choice.

Lower-case 'b' as the first character of a Bishop move is not acceptable in
the variations files.

Duplicate detection is not guaranteed to be exact. The -Z flag should give
slightly more accurate detection as it uses values for the end-position and
move sequence, whereas these are XORed, to save space, if -Z is not used.

The results of the -x, -v, and -t/-T search criteria are AND-ed together.
There might be occasions when you wanted to search for games that matched
either positional variations or textual variations at the same time, for
instance. This requires multiple runs of pgn-extract.

The FEN string output with -F does not attempt to record the number of
halfmoves since the last pawn move or capture.

The -Wsan variation that allows selection of the output language is tied to
single-character piece descriptions. This does not support Russian usage,
for instance, in which the King is described as a character pair.

The Files

The distribution comes with the following files.
 COPYING        GNU General Public License
 README         this file.
 Makefile       see below.
 Makefile.dos   see below.
 Makefile.ux    a copy of Makefile
 apply.[ch]     functions concerned with applying moves to a board.
 argsfile.[ch]  functions concerned with command line argument processing.
 bool.h         Boolean type definition.
 decode.[ch]    functions for decoding the text of a move.
 defs.h         definitions relating to boards.
 eco.[ch]       functions for looking up ECO classifications.
 eco.pgn        PGN file of ECO classifications.
 end.[ch]       functions for looking for matching endgames.
 grammar.[ch]   the parser.
 hashing.[ch]   duplicate detection hash tables.
 lex.[ch]       the lexical analyser.
 lines.[ch]     functions for reading lines.
 lists.[ch]     functions for holding the extraction criteria.
 map.[ch]       functions for implementing move semantics.
 moves.[ch]     functions for collecting moves and variations.
 mymalloc.[ch]  functions for memory allocation.
 output.[ch]    functions concerned with outputing the games.
 pgn-extract.exea 32-bit DOS executable.
 taglist.h      constants for pgn.y.
 tokens.h       type definition for lexical tokens.
 typedef.h      type definitions.
The sources include a Makefile for the UNIX make program as well as one for
Borland's make. However, the UNIX make program also works with the Djgpp
gcc compiler for DOS (see Portability).

Portability

pgn-extract is regularly used under DOS (using the Delorie free C compiler
- http://www.delorie.com/djgpp/) Solaris (Gnu C) and various versions of
Linux. I haven't managed to put a Mac version together.

Acknowledgements

I would like to thank all those who used the program and made suggestions
for things to add. In particular, thanks to Michael Kerry whose help led to
better determination of game boundaries in earlier versions, and V. Armando
Sole whose own filter program was the inspiration for adding textual
variation permutations. John Brogan suggested adding the ! notation to the
variation file and provided the spur for duplicate detection. He also
supplied the original code for soundex matching (-S). He also provided the
code for soundex matching. Jaroslav Poriz, Ron Leamon, Ed Leonard, Charles
Frohman, and Robert Wilhelm helped with testing at various times. Bernhard
Maerz was instrumental in encouraging the inclusion of ECO classification
and material balance matches, and has provided a large number of ideas for
future versions! He and Peter Otterstaetter suggested the relational
operators in tag files, with Peter also providing the spur to make
duplicate detection work with bigger game files (-Z) and doing some very
useful testing for me. Kayvan Sylvan requested long algebraic output and
identified an error in ECO classification. Cameron Hayne suggested matching
on the number of moves in a game. Owen D. Lyne suggested extension of the
-E flag, and both tested and provided diagnostic data to help refine the
ECO classification aspects of the program. Karl-Martin Skontorp provided
the incentive and testing help that enabled me to add the -Wepd option.
Thanks to all of those people on the net who provide games in PGN format.
Finally, thanks, of course, to Steven Edwards (sje@mv.mv.com) for his work
on developing the PGN standard.

License

pgn-extract: a Portable Game Notation (PGN) extractor.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation; either version 1, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc., 675
Mass Ave, Cambridge, MA 02139, USA.

David Barnes may be contacted as D.J.Barnes@kent.ac.uk or via
http://www.cs.kent.ac.uk/people/staff/djb/

Changes to the Original Release

   * 19th October 2005. Added language-specific letters to -Welalg
     following a suggestion from Folkert van Heusden.
   * 1st May 2004: Fixed an error with ECO classification that
     was causing the file list to be out of sync.
   * 29th April 2004: Buffered game text before outputting it,
     so that trailing spaces on lines (which violate the PGN spec)
     can be deleted.
     Games with zero moves are now acceptable.
   * 26th April 2004: Slight modification to one of the hashing
     values made in order to try to avoid clashes in ECO matches.
     ECO matches now have a discretion of up to 6 half moves.
   * 13th February 2002: Added -Welalg as an output format following
     a suggestion from Rafal Furdzik.
   * 27th March 2001
        o Added output of EPD via -Wepd.
        o Fixed a long standing error in FEN castling rights. These were
          not being withdrawn if a Rook was captured on its home square.
          Pointed out by Karl-Martin Skontorp, who also provided the
          incentive to add -Wepd.
   * 26th April 2000 Added the -R flag for tag ordering.
   * 22nd April 2000 Completed implementation of -A to work with all flags.
   * 21st April 2000
        o Added the -F flag.
        o Added support for reading Russian source files.
   * 11th April 2000
        o Added the -A flag.
        o Extended usage of -Wsan to support output in different languages.
        o Usage of -e with -7 retains an ECO tag in matched games.
        o FEN tags with the -t flag are used as positional matches
          (equivalent to -x matches).
        o Non-standard tags are now retained in game output.
   * 12th January 2000 C compiler with Red Hat Linux 6 was no longer happy
     with static initialisations involving stdin, stdout and stderr.
     Changes made to lex.c and main.c to work around this. Pointed out by
     Mladen Bestvina.
   * 18th October 1999 Numbers greater than 3 allowed with -E, at the
     request of Owen Lyne.
   * 15th December 1997 Treat \r as WHITESPACE (for DOS files).
   * 8th June 1997 Added -b flag to set bounds on the number of moves in a
     game to be matched.
   * 2nd May 1997 Corrected small error when strings were not terminated
     properly. In tags, this resulted in the corrected tag ending in ]"]
     instead of "].
   * 17th February 1997 Added a little more error recovery.
   * 15th November 1996 Added -Z.
   * 23rd Sep 1996 It is no longer necessary to omit move numbers from the
     variations files (-v and -x). This makes it easier to cut and paste
     games of interest into these files.
   * 28th Jun 1996 It is no longer necessary to terminate the tag file
     (-t). Relational operators added in the tag file (-t). Added -E flag.
   * 7th May 1996 Corrected failure to make ECO classification when
     combined with -x. Added lalg and halg as long algebraic output
     formats.
   * 9th Oct 1995 Add -#
   * 25th Sep 1995: Default to reading stdin if no file arguments are
     provided.
   * 24th Jul 1995: Added setup from FEN tags.
   * 18th Jul 1995:
        o Added material balance matches with -z.
        o Added 'L' as a minor piece letter in ending files.
   * 14th Jul 1995: Made the order of arguments immaterial.
   * 5th Jul 1995:
        o Added ECO classification with -e.
        o Fixed false partial substring matches with -v, e.g. textual
          variation move Nc6 is now no longer matched by game move c6.
   * 22nd Mar 1995: Made permutation matching with -v the default and added
     -P to suppress it.
   * Jan 1995: Added -n and -L.
   * 17th Nov 1994: Liberated the program from using YACC and Lex.
   * 13th Oct 1994: Released test version with ChessMaster output.
   * 20th Sep 1994: Added move rewriting and -W flag.
   * 7th Sep 1994: Added -D flag.
   * 6th Sep 1994: Added -C and -V flags and soundex matching.
   * 5th Sep 1994:
        o Integrated the positional variation code from a separately
          developed program.
        o Added -N flag.
        o Added ! to the textual variation syntax.
        o Removed the writing to extract.pgn that was present in an earlier
          unreleased version.
        o Added -d flag.
   * 8th Jul 1994:
        o Added -o flag.
        o Discarded writing to standard output in DOS version because of
          extensive problems trying to make this work with redirected
          output. Instead, output is written to the file extract.pgn.
   * 6th Jul 1994: Added -7 flag.
   * 9th May 1994: Added -p flag for variation permutations.
   * 6th May 1994: Added * as a don't-care move in variations files.
   * 26th Apr 1994: Added the -t flag for files of extraction criteria.
   * 25th Apr 1994: Added the -T flag for extraction criteria.
   * 22nd Apr 1994: Added the -f flag for handling lists of PGN files.
   * 13th Apr 1994:
        o Cleaned up the game-length determination by reading/writing files
          in binary-mode.
        o Added -a flag for appending to existing .pgn files.
        o Added multiple input files.
        o Made verbose output the default behaviour.

  ------------------------------------------------------------------------
Copyright (C) 1994-2005 David Barnes
D.J.Barnes@kent.ac.uk
Date of this version: 19th October 2005
Version Number: 16.0