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File: coreutils.info, Node: ptx invocation, Next: tsort invocation, Prev: comm invocation, Up: Operating on sorted files
7.5 'ptx': Produce permuted indexes
===================================
'ptx' reads a text file and essentially produces a permuted index, with
each keyword in its context. The calling sketch is either one of:
ptx [OPTION ...] [FILE ...]
ptx -G [OPTION ...] [INPUT [OUTPUT]]
The '-G' (or its equivalent: '--traditional') option disables all GNU
extensions and reverts to traditional mode, thus introducing some
limitations and changing several of the program's default option values.
When '-G' is not specified, GNU extensions are always enabled. GNU
extensions to 'ptx' are documented wherever appropriate in this
document. *Note Compatibility in ptx::, for the full list.
Individual options are explained in the following sections.
When GNU extensions are enabled, there may be zero, one or several
FILEs after the options. If there is no FILE, the program reads the
standard input. If there is one or several FILEs, they give the name of
input files which are all read in turn, as if all the input files were
concatenated. However, there is a full contextual break between each
file and, when automatic referencing is requested, file names and line
numbers refer to individual text input files. In all cases, the program
outputs the permuted index to the standard output.
When GNU extensions are _not_ enabled, that is, when the program
operates in traditional mode, there may be zero, one or two parameters
besides the options. If there are no parameters, the program reads the
standard input and outputs the permuted index to the standard output.
If there is only one parameter, it names the text INPUT to be read
instead of the standard input. If two parameters are given, they give
respectively the name of the INPUT file to read and the name of the
OUTPUT file to produce. _Be very careful_ to note that, in this case,
the contents of file given by the second parameter is destroyed. This
behavior is dictated by System V 'ptx' compatibility; GNU Standards
normally discourage output parameters not introduced by an option.
Note that for _any_ file named as the value of an option or as an
input text file, a single dash '-' may be used, in which case standard
input is assumed. However, it would not make sense to use this
convention more than once per program invocation.
* Menu:
* General options in ptx:: Options which affect general program behavior.
* Charset selection in ptx:: Underlying character set considerations.
* Input processing in ptx:: Input fields, contexts, and keyword selection.
* Output formatting in ptx:: Types of output format, and sizing the fields.
* Compatibility in ptx::
File: coreutils.info, Node: General options in ptx, Next: Charset selection in ptx, Up: ptx invocation
7.5.1 General options
---------------------
'-G'
'--traditional'
As already explained, this option disables all GNU extensions to
'ptx' and switches to traditional mode.
'--help'
Print a short help on standard output, then exit without further
processing.
'--version'
Print the program version on standard output, then exit without
further processing.
An exit status of zero indicates success, and a nonzero value
indicates failure.
File: coreutils.info, Node: Charset selection in ptx, Next: Input processing in ptx, Prev: General options in ptx, Up: ptx invocation
7.5.2 Charset selection
-----------------------
As it is set up now, the program assumes that the input file is coded
using 8-bit ISO 8859-1 code, also known as Latin-1 character set,
_unless_ it is compiled for MS-DOS, in which case it uses the character
set of the IBM-PC. (GNU 'ptx' is not known to work on smaller MS-DOS
machines anymore.) Compared to 7-bit ASCII, the set of characters which
are letters is different; this alters the behavior of regular expression
matching. Thus, the default regular expression for a keyword allows
foreign or diacriticized letters. Keyword sorting, however, is still
crude; it obeys the underlying character set ordering quite blindly.
'-f'
'--ignore-case'
Fold lower case letters to upper case for sorting.
File: coreutils.info, Node: Input processing in ptx, Next: Output formatting in ptx, Prev: Charset selection in ptx, Up: ptx invocation
7.5.3 Word selection and input processing
-----------------------------------------
'-b FILE'
'--break-file=FILE'
This option provides an alternative (to '-W') method of describing
which characters make up words. It introduces the name of a file
which contains a list of characters which can_not_ be part of one
word; this file is called the "Break file". Any character which is
not part of the Break file is a word constituent. If both options
'-b' and '-W' are specified, then '-W' has precedence and '-b' is
ignored.
When GNU extensions are enabled, the only way to avoid newline as a
break character is to write all the break characters in the file
with no newline at all, not even at the end of the file. When GNU
extensions are disabled, spaces, tabs and newlines are always
considered as break characters even if not included in the Break
file.
'-i FILE'
'--ignore-file=FILE'
The file associated with this option contains a list of words which
will never be taken as keywords in concordance output. It is
called the "Ignore file". The file contains exactly one word in
each line; the end of line separation of words is not subject to
the value of the '-S' option.
'-o FILE'
'--only-file=FILE'
The file associated with this option contains a list of words which
will be retained in concordance output; any word not mentioned in
this file is ignored. The file is called the "Only file". The
file contains exactly one word in each line; the end of line
separation of words is not subject to the value of the '-S' option.
There is no default for the Only file. When both an Only file and
an Ignore file are specified, a word is considered a keyword only
if it is listed in the Only file and not in the Ignore file.
'-r'
'--references'
On each input line, the leading sequence of non-white space
characters will be taken to be a reference that has the purpose of
identifying this input line in the resulting permuted index. *Note
Output formatting in ptx::, for more information about reference
production. Using this option changes the default value for option
'-S'.
Using this option, the program does not try very hard to remove
references from contexts in output, but it succeeds in doing so
_when_ the context ends exactly at the newline. If option '-r' is
used with '-S' default value, or when GNU extensions are disabled,
this condition is always met and references are completely excluded
from the output contexts.
'-S REGEXP'
'--sentence-regexp=REGEXP'
This option selects which regular expression will describe the end
of a line or the end of a sentence. In fact, this regular
expression is not the only distinction between end of lines or end
of sentences, and input line boundaries have no special
significance outside this option. By default, when GNU extensions
are enabled and if '-r' option is not used, end of sentences are
used. In this case, this REGEX is imported from GNU Emacs:
[.?!][]\"')}]*\\($\\|\t\\| \\)[ \t\n]*
Whenever GNU extensions are disabled or if '-r' option is used, end
of lines are used; in this case, the default REGEXP is just:
\n
Using an empty REGEXP is equivalent to completely disabling end of
line or end of sentence recognition. In this case, the whole file
is considered to be a single big line or sentence. The user might
want to disallow all truncation flag generation as well, through
option '-F ""'. *Note Syntax of Regular Expressions:
(emacs)Regexps.
When the keywords happen to be near the beginning of the input line
or sentence, this often creates an unused area at the beginning of
the output context line; when the keywords happen to be near the
end of the input line or sentence, this often creates an unused
area at the end of the output context line. The program tries to
fill those unused areas by wrapping around context in them; the
tail of the input line or sentence is used to fill the unused area
on the left of the output line; the head of the input line or
sentence is used to fill the unused area on the right of the output
line.
As a matter of convenience to the user, many usual backslashed
escape sequences from the C language are recognized and converted
to the corresponding characters by 'ptx' itself.
'-W REGEXP'
'--word-regexp=REGEXP'
This option selects which regular expression will describe each
keyword. By default, if GNU extensions are enabled, a word is a
sequence of letters; the REGEXP used is '\w+'. When GNU extensions
are disabled, a word is by default anything which ends with a
space, a tab or a newline; the REGEXP used is '[^ \t\n]+'.
An empty REGEXP is equivalent to not using this option. *Note
Syntax of Regular Expressions: (emacs)Regexps.
As a matter of convenience to the user, many usual backslashed
escape sequences, as found in the C language, are recognized and
converted to the corresponding characters by 'ptx' itself.
File: coreutils.info, Node: Output formatting in ptx, Next: Compatibility in ptx, Prev: Input processing in ptx, Up: ptx invocation
7.5.4 Output formatting
-----------------------
Output format is mainly controlled by the '-O' and '-T' options
described in the table below. When neither '-O' nor '-T' are selected,
and if GNU extensions are enabled, the program chooses an output format
suitable for a dumb terminal. Each keyword occurrence is output to the
center of one line, surrounded by its left and right contexts. Each
field is properly justified, so the concordance output can be readily
observed. As a special feature, if automatic references are selected by
option '-A' and are output before the left context, that is, if option
'-R' is _not_ selected, then a colon is added after the reference; this
nicely interfaces with GNU Emacs 'next-error' processing. In this
default output format, each white space character, like newline and tab,
is merely changed to exactly one space, with no special attempt to
compress consecutive spaces. This might change in the future. Except
for those white space characters, every other character of the
underlying set of 256 characters is transmitted verbatim.
Output format is further controlled by the following options.
'-g NUMBER'
'--gap-size=NUMBER'
Select the size of the minimum white space gap between the fields
on the output line.
'-w NUMBER'
'--width=NUMBER'
Select the maximum output width of each final line. If references
are used, they are included or excluded from the maximum output
width depending on the value of option '-R'. If this option is not
selected, that is, when references are output before the left
context, the maximum output width takes into account the maximum
length of all references. If this option is selected, that is,
when references are output after the right context, the maximum
output width does not take into account the space taken by
references, nor the gap that precedes them.
'-A'
'--auto-reference'
Select automatic references. Each input line will have an
automatic reference made up of the file name and the line ordinal,
with a single colon between them. However, the file name will be
empty when standard input is being read. If both '-A' and '-r' are
selected, then the input reference is still read and skipped, but
the automatic reference is used at output time, overriding the
input reference.
'-R'
'--right-side-refs'
In the default output format, when option '-R' is not used, any
references produced by the effect of options '-r' or '-A' are
placed to the far right of output lines, after the right context.
With default output format, when the '-R' option is specified,
references are rather placed at the beginning of each output line,
before the left context. For any other output format, option '-R'
is ignored, with one exception: with '-R' the width of references
is _not_ taken into account in total output width given by '-w'.
This option is automatically selected whenever GNU extensions are
disabled.
'-F STRING'
'--flac-truncation=STRING'
This option will request that any truncation in the output be
reported using the string STRING. Most output fields theoretically
extend towards the beginning or the end of the current line, or
current sentence, as selected with option '-S'. But there is a
maximum allowed output line width, changeable through option '-w',
which is further divided into space for various output fields.
When a field has to be truncated because it cannot extend beyond
the beginning or the end of the current line to fit in, then a
truncation occurs. By default, the string used is a single slash,
as in '-F /'.
STRING may have more than one character, as in '-F ...'. Also, in
the particular case when STRING is empty ('-F ""'), truncation
flagging is disabled, and no truncation marks are appended in this
case.
As a matter of convenience to the user, many usual backslashed
escape sequences, as found in the C language, are recognized and
converted to the corresponding characters by 'ptx' itself.
'-M STRING'
'--macro-name=STRING'
Select another STRING to be used instead of 'xx', while generating
output suitable for 'nroff', 'troff' or TeX.
'-O'
'--format=roff'
Choose an output format suitable for 'nroff' or 'troff' processing.
Each output line will look like:
.xx "TAIL" "BEFORE" "KEYWORD_AND_AFTER" "HEAD" "REF"
so it will be possible to write a '.xx' roff macro to take care of
the output typesetting. This is the default output format when GNU
extensions are disabled. Option '-M' can be used to change 'xx' to
another macro name.
In this output format, each non-graphical character, like newline
and tab, is merely changed to exactly one space, with no special
attempt to compress consecutive spaces. Each quote character: '"'
is doubled so it will be correctly processed by 'nroff' or 'troff'.
'-T'
'--format=tex'
Choose an output format suitable for TeX processing. Each output
line will look like:
\xx {TAIL}{BEFORE}{KEYWORD}{AFTER}{HEAD}{REF}
so it will be possible to write a '\xx' definition to take care of
the output typesetting. Note that when references are not being
produced, that is, neither option '-A' nor option '-r' is selected,
the last parameter of each '\xx' call is inhibited. Option '-M'
can be used to change 'xx' to another macro name.
In this output format, some special characters, like '$', '%', '&',
'#' and '_' are automatically protected with a backslash. Curly
brackets '{', '}' are protected with a backslash and a pair of
dollar signs (to force mathematical mode). The backslash itself
produces the sequence '\backslash{}'. Circumflex and tilde
diacritical marks produce the sequence '^\{ }' and '~\{ }'
respectively. Other diacriticized characters of the underlying
character set produce an appropriate TeX sequence as far as
possible. The other non-graphical characters, like newline and
tab, and all other characters which are not part of ASCII, are
merely changed to exactly one space, with no special attempt to
compress consecutive spaces. Let me know how to improve this
special character processing for TeX.
File: coreutils.info, Node: Compatibility in ptx, Prev: Output formatting in ptx, Up: ptx invocation
7.5.5 The GNU extensions to 'ptx'
---------------------------------
This version of 'ptx' contains a few features which do not exist in
System V 'ptx'. These extra features are suppressed by using the '-G'
command line option, unless overridden by other command line options.
Some GNU extensions cannot be recovered by overriding, so the simple
rule is to avoid '-G' if you care about GNU extensions. Here are the
differences between this program and System V 'ptx'.
* This program can read many input files at once, it always writes
the resulting concordance on standard output. On the other hand,
System V 'ptx' reads only one file and sends the result to standard
output or, if a second FILE parameter is given on the command, to
that FILE.
Having output parameters not introduced by options is a dangerous
practice which GNU avoids as far as possible. So, for using 'ptx'
portably between GNU and System V, you should always use it with a
single input file, and always expect the result on standard output.
You might also want to automatically configure in a '-G' option to
'ptx' calls in products using 'ptx', if the configurator finds that
the installed 'ptx' accepts '-G'.
* The only options available in System V 'ptx' are options '-b',
'-f', '-g', '-i', '-o', '-r', '-t' and '-w'. All other options are
GNU extensions and are not repeated in this enumeration. Moreover,
some options have a slightly different meaning when GNU extensions
are enabled, as explained below.
* By default, concordance output is not formatted for 'troff' or
'nroff'. It is rather formatted for a dumb terminal. 'troff' or
'nroff' output may still be selected through option '-O'.
* Unless '-R' option is used, the maximum reference width is
subtracted from the total output line width. With GNU extensions
disabled, width of references is not taken into account in the
output line width computations.
* All 256 bytes, even ASCII NUL bytes, are always read and processed
from input file with no adverse effect, even if GNU extensions are
disabled. However, System V 'ptx' does not accept 8-bit
characters, a few control characters are rejected, and the tilde
'~' is also rejected.
* Input line length is only limited by available memory, even if GNU
extensions are disabled. However, System V 'ptx' processes only
the first 200 characters in each line.
* The break (non-word) characters default to be every character
except all letters of the underlying character set, diacriticized
or not. When GNU extensions are disabled, the break characters
default to space, tab and newline only.
* The program makes better use of output line width. If GNU
extensions are disabled, the program rather tries to imitate System
V 'ptx', but still, there are some slight disposition glitches this
program does not completely reproduce.
* The user can specify both an Ignore file and an Only file. This is
not allowed with System V 'ptx'.
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