Device Control Commands (The GNU Troff Manual)

#### 6.1.2.4 Device Control Commands

Each device control command starts with the letter ‘`x`’, followed by a space character (optional or arbitrary space or tab in `gtroff`) and a subcommand letter or word; each argument (if any) must be preceded by a syntactical space. All ‘`x`’ commands are terminated by a syntactical line break; no device control command can be followed by another command on the same line (except a comment).

The subcommand is basically a single letter, but to increase readability, it can be written as a word, i.e., an arbitrary sequence of characters terminated by the next tab, space, or newline character. All characters of the subcommand word but the first are simply ignored. For example, `gtroff` outputs the initialization command ‘`x i`’ as ‘`x init`’ and the resolution command ‘`x r`’ as ‘`x res`’.

In the following, the syntax element ‹line break› means a syntactical line break (see Separation).

`xF name‹line break›`

  The ‘`F`’ stands for Filename.

  Use name as the intended name for the current file in error reports. This is useful for remembering the original file name when `gtroff` uses an internal piping mechanism. The input file is not changed by this command. This command is a `gtroff` extension.

`xf n s‹line break›`

  The ‘`f`’ stands for font.

  Mount font position n (a non-negative integer) with font named s (a text word). See Font Positions.

`xH n‹line break›`

  The ‘`H`’ stands for Height.

  Set glyph height to n (a positive integer in scaled points ‘`z`’). AT&T `troff` uses the unit points (‘`p`’) instead. See Output Language Compatibility.

`xi‹line break›`

  The ‘`i`’ stands for init.

  Initialize device. This is the third command of the prologue.

`xp‹line break›`

  The ‘`p`’ stands for pause.

  Parsed but ignored. The AT&T `troff` manual documents this command as

      pause device, can be restarted

  but GNU `troff` output drivers do nothing with this command.

`xr n h v‹line break›`

  The ‘`r`’ stands for resolution.

  Resolution is n, while h is the minimal horizontal motion, and v the minimal vertical motion possible with this device; all arguments are positive integers in basic units ‘`u`’ per inch. This is the second command of the prologue.

`xS n‹line break›`

  The ‘`S`’ stands for Slant.

  Set slant to n (an integer in basic units ‘`u`’).

`xs‹line break›`

  The ‘`s`’ stands for stop.

  Terminates the processing of the current file; issued as the last command of any intermediate `troff` output.

`xt‹line break›`

  The ‘`t`’ stands for trailer.

  Generate trailer information, if any. In GNU `troff`, this is ignored.

`xT xxx‹line break›`

  The ‘`T`’ stands for Typesetter.

  Set the name of the output driver to xxx, a sequence of non-whitespace characters terminated by whitespace. The possible names correspond to those of `groff`’s `-T` option. This is the first command of the prologue.

`xu n‹line break›`

  The ‘`u`’ stands for underline.

  Configure underlining of spaces. If n is 1, start underlining of spaces; if n is 0, stop underlining of spaces. This is needed for the `cu` request in `nroff` mode and is ignored otherwise. This command is a `gtroff` extension.

`xX anything‹line break›`

  The ‘`x`’ stands for X-escape.

  Send string anything uninterpreted to the device. If the line following this command starts with a ‘`+`’ character this line is interpreted as a continuation line in the following sense. The ‘`+`’ is ignored, but a newline character is sent instead to the device, the rest of the line is sent uninterpreted. The same applies to all following lines until the first character of a line is not a ‘`+`’ character. This command is generated by the `gtroff` escape sequence `\X`. The line-continuing feature is a `gtroff` extension.