Info Node: (textutils.info)Input processing in ptx
(textutils.info)Input processing in ptx
Word selection and input processing
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`-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. In the case there are both
an Only file and an Ignore file, a word will be subject to be a
keyword only if it is given in the Only file and not given in the
Ignore file.
`-r'
`--references'
On each input line, the leading sequence of non white characters
will be taken to be a reference that has the purpose of
identifying this input line on the produced permuted index. For
more information about reference production, see Note:Output
formatting in ptx. 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, there is other
distinction between end of lines or end of sentences than the
effect of this regular expression, 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, the precise 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, as found in 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, letting the
default dive in. *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.