| grotty(1) | User Commands | grotty(1) |
grotty - groff output driver for typewriter-like (terminal) devices
grotty |
[-dfho] [-i|-r] [-F dir] [file ...] |
grotty -c |
[-bBdfhouU] [-F dir] [file ...] |
grotty |
--help |
grotty |
-v |
grotty |
--version |
The GNU roff TTY (“Teletype”) output driver translates the output of gtroff(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.
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.
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).
grotty understands one device control function produced by the roff \X escape sequence in a document.
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.
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.
--help displays a usage message, while -v and --version show version information; all exit afterward.
grotty is intended only for simple documents.
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
“Control Functions for Coded Character Sets” (ECMA-48) 5th edition, Ecma International, June 1991. A gratis version of ISO 6429, this document includes a normative description of SGR escape sequences. Available at http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-048.pdf.
“Hyperlinks in Terminal Emulators”, Egmont Koblinger.
groff(1), gtroff(1), groff_out(5), groff_font(5), groff_char(7), ul(1), more(1), less(1), man(1)
| 2 July 2023 | groff 1.23.0 |