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(textutils.info)Input processing in ptx

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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.  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.