nroff/troff initializes the formatting environment. For example, unless you reset the line length, nroff/troff uses 6.5 inches. Most requests can change the default environment, and those that can are listed in Table 12-1. The second column lists the initial or default value in effect before the request is used. If no initial value applies, a hyphen (–) is used. The third column shows the effect if a request's optional argument is not used. Here, a hyphen is used if the request doesn't accept an argument or if the argument is required.
| Request | Initial Value | If No Argument | Description |
|---|---|---|---|
| .ad | Justify | Justify | Adjust margins. |
| .af | Lowercase arabic | – | Assign a format to a register. |
| .am | – | End call with .. | Append to a macro. |
| .bd | Off | – | Embolden font. |
| .c2 | ' | ' | Set no-break control character. |
| .cc | . | . | Set control character. |
| .ce | Off | Center one line | Center lines. |
| .ch | – | Turn off trap | Change trap position. |
| .cs | Off | – | Set constant-width spacing. |
| .cu | Off | One line | Continuous underline/italicize. |
| .da | – | End the diversion | Divert text and append to a macro. |
| .de | – | End macro with .. | Define a macro. |
| .di | – | End the diversion | Divert text to a macro. |
| .dt | – | Turn off trap | Set a diversion trap. |
| .ec | \ | \ | Set escape character. |
| .eo | On | – | Turn off escape character. |
| .ev | 0 | Previous environment | Change environment (push down). |
| .fc | Off | Off | Set field delimiter and pad character. |
| .fi | Fill | – | Fill lines. |
| .fp | 1=R 2=I 3=B 4=S |
– | Mount font (on positions 1–4). |
| .ft | Roman | Previous font | Set font. |
| .hc | \% | \% | Set hyphenation character. |
| .hy | Mode 1 | Mode 1 | Set hyphenation mode. |
| .ig | – | End with .. | Suppress (ignore) text in output. |
| .in | 0 | Previous indent | Indent. |
| .it | – | Turn off trap | Set a trap for input line counting. |
| .lc | . | None | Set leader character. |
| .lg | Off (nroff) On (troff) |
On | Ligature mode. |
| .ll | 6.5 inches | Previous line length | Set line length. |
| .ls | Single-space | Previous mode | Set line spacing. |
| .lt | 6.5 inches | Previous title length | Set length of title. |
| .mc | – | Turn off | Set the margin character. |
| .mk | – | Internal | Mark vertical position. |
| .na | Adjust | – | Don't adjust margins. |
| .ne | – | One vertical line | Keep lines on same page if there's room. |
| .nf | Fill | – | Don't fill lines. |
| .nh | On | – | Turn off hyphenation. |
| .nm | Off | Off | Line-numbering mode. |
| .nn | – | One line | Don't number next N lines. |
| .ns | Space mode | – | Enable no-space mode. |
| .nx | – | End of file | Go to a file. |
| .pc | % | Off | Set page character. |
| .pl | 11 inches | 11 inches | Set page length. |
| .pn | Page 1 | – | Set page number. |
| .po | 0 (nroff); 26/27 inch (otroff) 1 inch (ditroff) |
Previous offset | Change page offset. |
| .ps | 10 | Previous point size | Set point size. |
| .rd | – | Ring bell | Read from the terminal. |
| .rt | – | Internal | Return to marked vertical place. |
| .sp | – | One vertical line | Output blank spacing. |
| .ss | 12/36 em | Ignored | Set character spacing. |
| .sv | – | One vertical line | Save (store) spacing. |
| .ta | 8 en (nroff); 1/2 inch (troff) | – | Define tab settings. |
| .tc | – | – | Set tab repetition character. |
| .ti | 0 | – | Indent next line. |
| .tm | – | Newline | Print a message, then continue. |
| .tr | – | – | Translate pairs of characters on output. |
| .uf | Italic | Italic | Set font for underlining. |
| .ul | 0 | One line | Underline/italicize. |
| .vs | 1/6 inch (nroff); 12 points (troff) | Previous value | Set vertical spacing for lines. |
Comments in nroff/troff begin with \". Lines beginning with . that contain an unknown request are ignored. In general, don't put leading whitespace on your text lines. This causes a break, and nroff and troff honors the leading whitespace literally.
Note: the canonical reference for nroff/troff is Bell Labs Computing Science Technical Report #54, Troff User's Manual, by J.F. Ossanna and B.W. Kernighan. It is available in PostScript from http://cm.bell-labs.com/cm/cs/cstr/54.ps.gz. You should read it if you plan to do any serious work in nroff/troff (such as writing or modifying macro packages). This document explains the ideas of diversions, environments, fields, registers, strings, and traps.
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