col(C)                          19 June 1992                          col(C)


 Name

    col - filter reverse linefeeds

 Syntax

    col [ -bfxp ]

 Description

    col prepares output from processes, such as the text formatter nroff(CT),
    for output on devices that limit or do not allow reverse or half-line
    motions.  col is typically used to process nroff output text that con-
    tains tables generated by the tbl program. A typical command line might
    be:

       tbl file | nroff | col | lpr

    col takes the following options:

    -b  Assumes the output device in use is not capable of backspacing.  If
        two or more characters appear in the same place, col outputs the last
        character read.

    -f  Allows forward half linefeeds.  If not given, col accepts half line
        motions in its input, but text that would appear between lines is
        moved down to the next full line. Reverse full and half linefeeds are
        never allowed with this option.

    -x  Prevents conversion of whitespace to tabs on output. col normally
        converts whitespace to tabs wherever possible to shorten printing
        time.

    -p  Causes col to ignore unknown escape sequences found in its input and
        pass them to the output as regular characters.  Because these charac-
        ters are subject to overprinting from reverse line motions, the use
        of this option is discouraged unless the user is fully aware of the
        position of the escape sequences.

    col assumes that the ASCII control characters SO (octal 016) and SI
    (octal 017) start and end text in an alternate character set.  If you
    have a reverse linefeed (ESC 7), reverse half linefeed (ESC 8), or for-
    ward half linefeed (ESC 9), within an SI-SO sequence, the ESC 7, 8 and 9
    are still recognized as line motions.

    On input, the only control characters col accepts are Space, Backspace,
    Tab, Return, Newline, reverse linefeed (ESC 7), reverse half linefeed
    (ESC 8), forward half linefeed (ESC 9), alternate character start(SI),
    alternate character end (SO), and vertical tag (VT).  (The VT character
    is an alternate form of full reverse linefeed, included for compatibility
    with some earlier programs of this type.)  All other non-printing charac-
    ters are ignored.

 See also

    nroff(CT), tbl(CT)

 Notes

    col cannot back up more than 128 lines.

    col allows at most 800 characters, including backspaces, on a line.

    Vertical motions that would back up over the first line of the document
    are ignored.  Therefore, the first line must not contain any super-
    scripts.

 Standards conformance

    col is conformant with:

    AT&T SVID Issue 2;
    and X/Open Portability Guide, Issue 3, 1989.