Home – troff and its companion programs
troff reads one or more files containing troff source and produces device-independent troff output. This device-independent output is then turned into a suitable format for a particular device by a post-processor. Because drawing equations, tables, etc., in low-level troff source is tedious, pre-processors exist which recognise higher level descriptions in their own ‘little languages’ interspersed with the troff source and replace it with the low-level equivalent. Similarly, ‘macro packages’ exist which contain definitions of often used pieces of troff source saving repetition and giving consistency throughout a document.
In the diagram, tbl is shown as the first pre-processor and is used for typesetting tables. Next, pic, a pre-processor for drawing pictures, like the diagram itself, replaces any picture definitions with troff commands. Finally, troff itself gets to layout the pages of the document and outputs a device independent description. As letter.tr uses the ‘mm’ macro package troff reads in the tmac.m file containing the macro definitions. troff's device-independent output is then turned into PostScript using one of the post-processors, grops.
tbl is used to produce elegant tables. It assumes lines between ‘.TS’ and ‘.TE’ are a table description in its own little language. Here's an example table based on one given in M. E. Lesk's paper on tbl.
This is its source code.
.TS tab(:); c s s c | c | c l | l | n. Major New York Bridges = Bridge:Designer:Length _ Brooklyn:J. A. Roebling:1595 Manhattan:G. Lindenthal: 1470 Williamsburg:L. L. Buck:1600 _ Queensborough:Palmer &:1182 \^: Hornbostel:\^ _ Triborough:O. H. Ammann:1380 \^:\^:383 _ Bronx Whitestone:O. H. Ammann:2300 Throgs Neck:O. H. Ammann:1800 _ George Washington:O. H. Ammann:3500 _ .TE
Similarly, pic draws pictures from the descriptions bounded by ‘.PS’ and ‘.PE’ lines. The diagram at the top of this page was drawn using
.PS lineht = lineht / 2 box "\fIletter.tr\fP" arrow circle "tbl" arrow Eqn: circle "eqn" arrow Troff: circle "troff" arc cw line down arc cw left arrow circle "grops" arrow box "\fIletter.ps\fP" up line <- from Troff.n arc line box "\fItmac.m\fP" .PE
Neatly typeset equations are produced by eqn. This one is from Brian W. Kernighan and Lorinda L. Cherry's eqn user guide.
.EQ
G(z) ~=~ e sup { ln ~ G(z) }
~=~ exp left ( sum from k>=1 { S sub k z sup k } over k right )
~=~ prod from k>=1 e sup { S sub k z sup k /k }
.EN
chem is an awk script that produces pic output depicting a chemical structure diagram, i.e. it's a pre-processor for a pre-processor. Here's Lysergic acid dethylamide, also known as LSD, courtesy of Brian W. Kernighan's chem release.
.cstart
B: benzene pointing right
F: flatring5 pointing left put N at 5 double 3,4 with .V1 at B.V2
H below F.N
R: ring pointing right with .V4 at B.V6
front bond right from R.V6 ; H
R: ring pointing right with .V2 at R.V6 put N at 1 double 3,4
bond right from R.N ; CH3
back bond -60 from R.V5 ; H
bond up from R.V5 ; CO
bond right ; N(C2H5)2
.cend
dformat is an awk script that produces pic output depicting data structures that comprise of one record per line, with each record containing fields. It was written by Jon Bentley and described in his paper ‘DFORMAT — A Program for Typesetting Data Formats’.
Like chem, it produces pic output. Here's two examples, one from Bentley's paper, the other describes the layout of the X11 Window System's ConnSetup protocol reply.
.EQ
delim @@
.EN
.begin dformat
style bitwid 0.08
style charwid 0
style recspread 0.3
noname
--16 Frame
--16 Frame
A1: --16 Frame
--16 Frame
--8-dashed ...
noname
A2: 8--8 Flags
8--8 Status
--8 @roman Chunk sub 1@
B1: --8 @roman Chunk sub 2@
--8-dashed ...
--8 @roman Chunk sub m@
16--16 CRC
A3: 8--8 Flags
noname
B2: 8--8 @roman Data sub 1@
8--8 @roman Data sub 2@
8--8 @roman Data sub 3@
8--8 @roman Data sub 4@
--8-dashed ...
8--8 @roman Data sub {n-1}@
8--8 @roman Data sub n@
6--6 Length
B3: 10--10 Channel #
pic line dotted from A1.sw to A2.nw
pic line dotted from A1.se to A3.ne
pic line dotted from B1.sw to B2.nw
pic line dotted from B1.se to B3.ne
.end
.begin dformat
style bitwid 0.16
style recspread 0
noname
0-31-32 release
noname
32-63-32 ridBase
noname
64-95-32 ridMask
noname
96-127-32 motionBufferSize
noname
128-143-16 nbytesVendor
144-159-16 maxRequestSize
noname
160-167-8 numRoots
168-175-8 numFormats
176-183-8 imageByteOrder
184-191-8 bitmapBitOrder
noname
192-199-8 bitmapScanlineUnit
200-207-8 bitmapScanlinePad
208-215-8 minKeyCode
216-223-8 maxKeyCode
noname
224-255-32-dashed pad2
.end
grap. dot. refer. bib. ideal. grn. g3.
Literate programming. One or two of the Stevens books mentions using ‘Dave Hanson's loom program’... is the source available anywhere? this looks hopeful: ftp://ftp.cs.princeton.edu/pub/people/drh/loom.tar.gz since it's on Hanson's own ftp space. DRH's home page is http://research.microsoft.com/~drh/
FPIC, LaTeX output only? — https://www.usenix.org/publications/library/proceedings/dsl97/full_papers/kamin/kamin_html/kamin.html
deroff — http://www.moria.de/~michael/deroff/
From: philippe@crabus.net Subject: Re: [Groff] Gantt Chart (fwd) Date: Sat, 20 Apr 2002 15:09:20 +0200 (CEST) > Is it possible that you may place the Tcl preprocessor on the Internet > somewhere for others to make use of in the future? Yes, but it's just a quick made tool. You can find it at: http://www.epita.fr:8000/~lamira_p/groff/
Copyright Ralph Corderoy, 2001, 2002, 2003.