Ubuntu Manpage: grotty - groff output driver for typewriter-like (terminal) devices

Name

       grotty - groff output driver for typewriter-like (terminal) devices

Synopsis

       grotty [-dfho] [-i|-r] [-F dir] [file ...]

       grotty -c [-bBdfhouU] [-F dir] [file ...]

       grotty --help

       grotty -v
       grotty --version

Description

The GNU roff TTY (“Teletype”) output driver translates the output of troff(1) into a form
suitable for typewriter-like devices, including terminal emulators. Normally, grotty is
invoked by groff(1) when the latter is given one of the “-T ascii”, “-T latin1”, -Tlatin1,
or “-T utf8” options on systems using ISO character encoding standards, or with
“-T cp1047” or “-T utf8” on EBCDIC-based hosts. (In this installation, ps is the default
output device.) Use groff's -P option to pass any options shown above to grotty. If no
file arguments are given, or if file is “-”, grotty reads the standard input stream.
Output is written to the standard output stream.

By default, grotty emits SGR escape sequences (from ISO 6429, popularly called “ANSI
escapes”) to change text attributes (bold, italic, underline, reverse video [“negative
image”] and colors). Devices supporting the appropriate sequences can view roff documents
using eight different background and foreground colors. Following ISO 6429, the following
colors are defined in tty.tmac: black, white, red, green, blue, yellow, magenta, and cyan.
Unrecognized colors are mapped to the default color, which is dependent on the settings of
the terminal. OSC 8 hyperlinks are produced for these devices.

In keeping with long-standing practice and the rarity of terminals (and emulators) that
support oblique or italic fonts, italicized text is represented with underlining by
default—but see the -i option below.

SGR and OSC support in pagers
When paging grotty's output with less(1), the latter program must be instructed to pass
SGR and OSC sequences through to the device; its -R option is one way to achieve this
(less version 566 or later is required for OSC 8 support). Consequently, programs like
man(1) that page roff documents with less must call it with an appropriate option.

Legacy output format
The -c option tells grotty to use an output format compatible with paper terminals, like
the Teletype machines for which roff and nroff were first developed but which are no
longer in wide use. SGR escape sequences are not emitted; bold, italic, and underlining
character attributes are thus not manipulated. Instead, grotty overstrikes, representing
a bold character c with the sequence “c BACKSPACE c”, an italic character c with the
sequence “_ BACKSPACE c”, and bold italics with “_ BACKSPACE c BACKSPACE c”. This
rendering is inherently ambiguous when the character c is itself the underscore.

The legacy output format can be rendered on a video terminal (or emulator) by piping
grotty's output through ul(1), which may render bold italics as reverse video. Some
implementations of more(1) are also able to display these sequences; you may wish to
experiment with that command's -b option. less renders legacy bold and italics without
requiring options. In contrast to the terminal output drivers of some other roff
implementations, grotty never outputs reverse line feeds. There is therefore no need to
filter its output through col(1).

Device control commands
grotty understands one device control function produced by the roff \X escape sequence in
a document.

\X'tty: link [uri [key=value] ...]'
Embed a hyperlink using the OSC 8 terminal escape sequence. Specifying uri starts
hyperlinked text, and omitting it ends the hyperlink. When uri is present, any
number of additional key/value pairs can be specified; their interpretation is the
responsibility of the pager or terminal. Spaces or tabs cannot appear literally in
uri, key, or value; they must be represented in an alternate form.

Device description files
If the DESC file for the character encoding contains the “unicode” directive, grotty emits
Unicode characters in UTF-8 encoding. Otherwise, it emits characters in a single-byte
encoding depending on the data in the font description files. See groff_font(5).

A font description file may contain a directive “internalname n” where n is a decimal
integer. If the 01 bit in n is set, then the font is treated as an italic font; if the 02
bit is set, then it is treated as a bold font.

Typefaces
grotty supports the standard four styles: R (roman), I (italic), B (bold), and BI (bold-
italic). Because the output driver operates in nroff mode, attempts to set or change the
font family or type size are ignored.

Options

--help displays a usage message, while -v and --version show version information; all exit
afterward.

-b Suppress the use of overstriking for bold characters in legacy output format.

-B Use only overstriking for bold-italic characters in legacy output format.

-c Use grotty's legacy output format (see subsection “Legacy output format” above).
SGR and OSC escape sequences are not emitted.

-d Ignore all \D drawing escape sequences in the input. By default, grotty renders
\D'l...' escape sequences that have at least one zero argument (and so are either
horizontal or vertical) using Unicode box drawing characters (for the utf8 device)
or the -, |, and + characters (for all other devices). grotty handles \D'p...'
escape sequences that consist entirely of horizontal and vertical lines similarly.

-f Emit a form feed at the end of each page having no output on its last line.

-F dir Prepend directory dir/devname to the search path for font and device description
files; name describes the output device's character encoding, one of ascii, latin1,
utf8, or cp1047.

-h Use literal horizontal tab characters in the output. Tabs are assumed to be set
every 8 columns.

-i Render oblique-styled fonts (I and BI) with the SGR attribute for italic text
rather than underlined text. Many terminals don't support this attribute; however,
xterm(1), since patch #314 (2014-12-28), does. Ignored if -c is also specified.

-o Suppress overstriking (other than for bold and/or underlined characters when the
legacy output format is in use).

-r Render oblique-styled fonts (I and BI) with the SGR attribute for reverse video
text rather than underlined text. Ignored if -c or -i is also specified.

-u Suppress the use of underlining for italic characters in legacy output format.

-U Use only underlining for bold-italic characters in legacy output format.

Environment

       GROFF_FONT_PATH
              A  list  of  directories in which to seek the selected output device's directory of
              device and font description files.  See troff(1) and groff_font(5).

       GROFF_NO_SGR
              If set, grotty's legacy output format is  used  just  as  if  the  -c  option  were
              specified; see subsection “Legacy output format” above.

Files

       /usr/share/groff/1.23.0/font/devascii/DESC
              describes the ascii output device.

       /usr/share/groff/1.23.0/font/devascii/F
              describes the font known as F on device ascii.

       /usr/share/groff/1.23.0/font/devcp1047/DESC
              describes the cp1047 output device.

       /usr/share/groff/1.23.0/font/devcp1047/F
              describes the font known as F on device cp1047.

       /usr/share/groff/1.23.0/font/devlatin1/DESC
              describes the latin1 output device.

       /usr/share/groff/1.23.0/font/devlatin1/F
              describes the font known as F on device latin1.

       /usr/share/groff/1.23.0/font/devutf8/DESC
              describes the utf8 output device.

       /usr/share/groff/1.23.0/font/devutf8/F
              describes the font known as F on device utf8.

       /usr/share/groff/1.23.0/tmac/tty.tmac
              defines macros for use with the ascii, cp1047, latin1, and utf8 output devices.  It
              is automatically loaded by troffrc when any of those output devices is selected.

       /usr/share/groff/1.23.0/tmac/tty-char.tmac
              defines fallback characters for use with grotty.  See nroff(1).

Limitations

       grotty is intended only for simple documents.

       • There is no support for fractional horizontal or vertical motions.

       • roff \D escape sequences producing anything other than horizontal and vertical lines are
         not supported.

       • Characters  above the first line (that is, with a vertical drawing position of 0) cannot
         be rendered.

       • Color handling differs from  other  output  drivers.   The  groff  requests  and  escape
         sequences  that set the stroke and fill colors instead set the foreground and background
         character cell colors, respectively.

Examples

       The following groff document exercises several features for which  output  device  support
       varies: (1) bold style; (2) italic (underline) style; (3) bold-italic style; (4) character
       composition by overstriking (“coöperate”); (5) foreground color; (6) background color; and
       (7) horizontal and vertical line-drawing.

              You might see \f[B]bold\f[] and \f[I]italic\f[].
              Some people see \f[BI]both\f[].
              If the output device does (not) co\z\[ad]operate,
              you might see \m[red]red\m[].
              Black on cyan can have a \M[cyan]\m[black]prominent\m[]\M[]
              \D'l 1i 0'\D'l 0 2i'\D'l 1i 0' look.
              .\" If in nroff mode, end page now.
              .if n .pl \n[nl]u

       Given the foregoing input, compare and contrast the output of the following.

              $ groff -T ascii file
              $ groff -T utf8 -P -i file
              $ groff -T utf8 -P -c file | ul