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 will be output.
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 will convert white space to tabs on output wherever possible to shorten printing time.
The ASCII control characters SO (\017) and SI (\016) 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 processed are space, backspace, tab, return, new-line, SI, SO, 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 will ignore any escape sequences unknown to it that are found in its input; the -p option may be used to cause col to output these 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.
col cannot back up more than 128 lines or handle more than 800 characters per line.
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.