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.
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:
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.
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.
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).
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.
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.
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.
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
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.
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
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 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.)
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:
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.
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:
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.
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.
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.
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 has slightly more potential to avoid false duplicates as it compares separate values for the end position and move sequence, whereas these are XORed to save space when -Z is not used. However, this will only make a difference and avoid false matches if two different games at the same hashtable index also produce identical XORed values.
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. |
| 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.exe | a 32-bit DOS executable. |
| taglist.h | constants for pgn.y. |
| tokens.h | type definition for lexical tokens. |
| typedef.h | type definitions. |
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@ukc.ac.uk
or via
http://www.cs.ukc.ac.uk/people/staff/djb/
Changes to the Original Release