col(1)                                                               col(1)




 NAME    [Toc]    [Back]
      col - filter reverse line-feeds and backspaces

 SYNOPSIS    [Toc]    [Back]
      col [-blfxp]

 DESCRIPTION    [Toc]    [Back]
      col reads from the standard input and writes onto the standard output.
      It performs the line overlays implied by reverse line feeds (ASCII
      code ESC-7), and by forward and reverse half-line feeds (ESC-9 and
      ESC-8).  col is particularly useful for filtering multi-column output
      made with the nroff .rt command, and output resulting from use of the
      tbl preprocessor (see nroff(1) and tbl(1)).

      If the -b option is given, col assumes that the output device in use
      is not capable of backspacing.  In this case, if two or more
      characters are to appear in the same place, only the last one read is
      output.

      If the -l option is given, col assumes the output device is a line
      printer (rather than a character printer) and removes backspaces in
      favor of multiply overstruck full lines.  It generates the minimum
      number of print operations necessary to generate the required number
      of overstrikes.  (All but the last print operation on a line are
      separated by carriage returns (\r); the last print operation is
      terminated by a newline (\n).)

      Although col accepts half-line motions in its input, it normally does
      not emit them on output.  Instead, text that would appear between
      lines is moved to the next lower full-line boundary.  This treatment
      can be suppressed by the -f (fine) option; in this case, the output
      from col may contain forward half-line feeds (ESC-9), but will still
      never contain either kind of reverse line motion.

      Unless the -x option is given, col converts white space to tabs on
      output wherever possible to shorten printing time.

      The ASCII control characters SO (\016) and SI (\017) are assumed by
      col to start and end text in an alternate character set.  The
      character set to which each input character belongs is remembered, and
      on output SI and SO characters are generated as appropriate to ensure
      that each character is printed in the correct character set.

      On input, the only control characters accepted are space, backspace,
      tab, return, new-line, SI , SO , and VT , (\013), and ESC followed by
      7, 8, or 9.  The VT character is an alternate form of full reverse
      line-feed, included for compatibility with some earlier programs of
      this type.  All other non-printing characters are ignored.

      Normally, col ignores any unrecognized escape sequences found in its
      input; the -p option can be used to cause col to output these



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 col(1)                                                               col(1)




      sequences as regular characters, subject to overprinting from reverse
      line motions.  The use of this option is highly discouraged unless the
      user is fully aware of the textual position of the escape sequences.

 EXTERNAL INFLUENCES    [Toc]    [Back]
    Environment Variables
      LANG provides a default value for the internationalization variables
      that are unset or null. If LANG is unset or null, the default value of
      "C" (see lang(5)) is used. If any of the internationalization
      variables contains an invalid setting, col will behave as if all
      internationalization variables are set to "C".  See environ(5).

      LC_ALL If set to a non-empty string value, overrides the values of all
      the other internationalization variables.

      LC_CTYPE determines the interpretation of text as single and/or
      multi-byte characters, the classification of characters as printable,
      and the characters matched by character class expressions in regular
      expressions.

      LC_MESSAGES determines the locale that should be used to affect the
      format and contents of diagnostic messages written to standard error
      and informative messages written to standard output.

      NLSPATH determines the location of message catalogues for the
      processing of LC_MESSAGES.

    International Code Set Support    [Toc]    [Back]
      Single- and multi-byte character code sets are supported.

 EXAMPLES    [Toc]    [Back]
      col is used most often with nroff and tbl.  A common usage is:

           tbl filename | nroff -man | col | more -s

      (very similar to the usual man(1) command).  This command allows
      vertical bars and outer boxes to be printed for tables.  The file is
      run through the tbl preprocessor, and the output is then piped through
      nroff, formatting the output using the -man macros.  The formatted
      output is then piped through col, which sets up the vertical bars and
      aligns the columns in the file.  The file is finally piped through the
      more command, which prints the output to the screen with underlining
      and highlighting substituted for italic and bold typefaces.  The -s
      option deletes excess space from the output so that multiple blank
      lines are not printed to the screen.

 SEE ALSO    [Toc]    [Back]
      nroff(1), tbl(1), ul(1), man(5).

 NOTES    [Toc]    [Back]
      The input format accepted by col matches the output produced by nroff



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 col(1)                                                               col(1)




      with either the -T37 or -Tlp options.  Use -T37 (and the -f option of
      col) if the ultimate disposition of the output of col is a device that
      can interpret half-line motions, and -Tlp otherwise.

 BUGS    [Toc]    [Back]
      Cannot back up more than 128 lines.  Cannot back up across page
      boundaries.

      There is a maximum limit for the number of characters, including
      backspaces and overstrikes, on a line.  The maximum limit is at least
      800 characters.

      Local vertical motions that would result in backing up over the first
      line of the document are ignored.  As a result, the first line must
      not have any superscripts.

 WARNINGS    [Toc]    [Back]
      This command is likely to be withdrawn from X/Open standards.
      Applications using this command might not be portable to other
      vendors' systems.

 STANDARDS CONFORMANCE    [Toc]    [Back]
      col: SVID2, SVID3, XPG2, XPG3


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