| 1 | .TH COL 1 |
| 2 | .SH NAME |
| 3 | col \- filter reverse line feeds |
| 4 | .SH SYNOPSIS |
| 5 | .B col [\|\-bfx\|] |
| 6 | .SH DESCRIPTION |
| 7 | .I Col |
| 8 | reads the standard input and writes the standard output. |
| 9 | It performs the line overlays implied by reverse line |
| 10 | feeds (ESC-7 in ASCII) |
| 11 | and by forward and reverse half line feeds (ESC-9 and ESC-8). |
| 12 | .I Col |
| 13 | is particularly useful for filtering multicolumn |
| 14 | output made with the `.rt' command of |
| 15 | .I nroff |
| 16 | and output resulting from use of the |
| 17 | .IR tbl (1) |
| 18 | preprocessor. |
| 19 | .PP |
| 20 | Although |
| 21 | .I col |
| 22 | accepts half line motions in its input, it normally does not |
| 23 | emit them on output. |
| 24 | Instead, text that would appear between lines is moved to the next lower |
| 25 | full line boundary. |
| 26 | This treatment can be suppressed by the |
| 27 | .B \-f |
| 28 | (fine) option; in this case |
| 29 | the output from |
| 30 | .I col |
| 31 | may contain forward half line feeds (ESC-9), but will still never contain |
| 32 | either kind of reverse line motion. |
| 33 | .PP |
| 34 | If the |
| 35 | .B \-b |
| 36 | option is given, |
| 37 | .I col |
| 38 | assumes that the output device in use is not capable of backspacing. |
| 39 | In this case, if several characters are to appear in the same place, |
| 40 | only the last one read will be taken. |
| 41 | .PP |
| 42 | The control characters SO (ASCII code 017), |
| 43 | and SI (016) are assumed |
| 44 | to start and end text in an alternate character set. |
| 45 | The character set (primary or alternate) associated with each printing |
| 46 | character read is remembered; on output, SO and SI characters are generated |
| 47 | where necessary to maintain the correct treatment of each character. |
| 48 | .PP |
| 49 | .I Col |
| 50 | normally converts white space to tabs to shorten printing time. |
| 51 | If the |
| 52 | .B \-x |
| 53 | option is given, this conversion is suppressed. |
| 54 | .PP |
| 55 | All control characters are removed from the input except space, |
| 56 | backspace, |
| 57 | tab, return, newline, ESC (033) followed by one of 7, 8, 9, SI, SO, and VT |
| 58 | (013). |
| 59 | This last character is an alternate form of full reverse line feed, for |
| 60 | compatibility with some other hardware conventions. |
| 61 | All other non-printing characters are ignored. |
| 62 | .SH "SEE ALSO" |
| 63 | troff(1), tbl(1), greek(1) |
| 64 | .SH BUGS |
| 65 | Can't back up more than 128 lines. |
| 66 | .br |
| 67 | No more than 800 characters, including backspaces, on a line. |