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Linux and Unix troff command

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troff syntax
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About troff

troff performs typesetting functions and formats documents. It is the major component of the document processing system developed by AT&T for Unix.

troff syntax

troff [-abcivzCERU] [-d cs] [-f fam] [-F dir] [-I dir] [-m name] [-M dir] 
      [-n num] [-o list] [-r cn] [-T name] [-w name] [-W name] [file ...]

Description And History

troff formats text for printers and character terminals, and is one of the most important pieces of software in Unix history.

Like roff, nroff and groff, troff is descended from a text formatting program called RUNOFF written by Jerome Saltzer for MIT's CTSS operating system in the mid-1960s. The name RUNOFF comes from the phrase "to run off a document," meaning to finalize a document, or prepare it for publication or presentation.

Later iterations of RUNOFF were called rf and then roff, and a version of roff was eventually written for Unix on a PDP-7. Eventually, it evolved in to nroff ("newer roff") and then troff ("typesetter roff"). The legendary Brian Kernighan eventually rewrote troff, giving it a more flexible syntax and designing it to be device-independent.

Although other typesetting software packages such as LaTeX have gained prominent usage throughout the years, troff is still used extensively in Unix, and is the default type formatter for man.

This documentation is for GNU version of the troff command, which is part of the groff package and commonly used on Linux.

Options

-a Generate an ASCII approximation of the typeset output.
-b Print a backtrace with each warning or error message. This backtrace should help track down the cause of the error. The line numbers given in the backtrace may not always be correct, for troff's idea of line numbers gets confused by as or am requests.
-c Disable color output (always disabled in compatibility mode).
-C Enable compatibility mode.
-dcs, -dname=s Define c or name to be a string s; c must be a one-letter name.
-E Inhibit all error messages of troff. Note that this doesn't affect messages output to standard error by macro packages using the tm or tm1 requests.
-ffam Use fam as the default font family.
-Fdir Search in directory (or directory path) dir for subdirectories devname (where name is the name of the device), and for the DESC file and font files. dir is scanned before all other font directories.
-i Read the standard input after all the named input files have been processed.
-Idir This option may be used to add a directory to the search path for files (both those on the command line and those named in .psbb requests). The search path is initialized with the current directory. This option may be specified more than once; the directories are then searched in the order specified (but before the current directory). If you want to make the current directory be read before other directories, add -I. at the appropriate place.

No directory search is performed for files with an absolute file name.
-mname Read in the file "name.tmac". If it isn't found, "tmac.name" is tried instead. It will be first searched for in:
  1. directories given with the -M command line option,
  2. then in directories given in the GROFF_TMAC_PATH environment variable,
  3. then in the current directory (only if in "unsafe" mode),
  4. the home directory,
  5. /usr/lib/groff/site-tmac,
  6. /usr/share/groff/site-tmac,
  7. and finally in /usr/share/groff/1.22.2/tmac.
-Mdir Search directory (or directory path) dir for macro files. This is scanned before all other macro directories.
-nnum Number the first page num.
-olist Output only pages in list, which is a comma-separated list of page ranges; n means print page n, m-n means print every page between m and n, -n means print every page up to n, n- means print every page from n. troff will exit after printing the last page in the list.
-rcn -rname=n Set number register c or name to n; c must be a one character name; n can be any troff numeric expression.
-R Don't load troffrc and troffrc-end.
-Tname Prepare output for device name, rather than the default ps.
-U Unsafe mode. This will enable the following requests: open, opena, pso, sy, and pi. For security reasons, these potentially dangerous requests are disabled otherwise. It will also add the current directory to the macro search path.
-v Print the version number.
-wname Enable warning name. Available warnings are described in the section WARNINGS below. For example, to enable all warnings, use -w all. Multiple -w options are allowed.
-Wname Inhibit warning name. Multiple -W options are allowed.
-z Suppress formatted output.

Warnings

The warnings that can be given by troff are divided into the following categories. The name associated with each warning is used by the -w and -W options; the number is used by the warn request, and by the .warn register; it is always a power of 2 to allow bitwise composition (any two codes can be combined additively to create a unique number).

Warnings, listed by bit:

bit code warning
0 1 char
1 2 number
2 4 break
3 8 delim
4 16 el
5 32 scale
6 64 range
7 128 syntax
8 256 di
9 512 mac
10 1024 reg
11 2048 tab
12 4096 right-brace
13 8192 missing
14 16384 input
15 32768 escape
16 65536 space
17 131072 font
18 262144 ig
19 524288 color
20 1048576 file

Descriptions:

warning code description
break 4 In fill mode, lines which could not be broken so that their length was less than the line length. This is enabled by default.
char 1 Non-existent characters. This is enabled by default.
color 524288 Color related warnings.
delim 8 Missing or mismatched closing delimiters.
di 256 Use of di or da without an argument when there is no current diversion.
el 16 Use of the el request with no matching ie request.
escape 32768 Unrecognized escape sequences. When an unrecognized escape sequence is encountered, the escape character is ignored.
file 1048576 Indicates a missing file for the mso request. Enabled by default.
font 131072 Non-existent fonts. This is enabled by default.
ig 262144 Invalid escapes in text ignored with the ig request. These are conditions that are errors when they do not occur in ignored text.
input 16384 Invalid input characters.
mac 512 Use of undefined strings, macros and diversions. When an undefined string, macro or diversion is used, that string is automatically defined as empty. So, in most cases, at most one warning will be given for each name.
missing 8192 Requests that are missing non-optional arguments.
number 2 Invalid numeric expressions. This is enabled by default.
range 64 Out of range arguments.
reg 1024 Use of undefined number registers. When an undefined number register is used, that register is automatically defined to have a value of 0. So, in most cases, at most one warning will be given for use of a particular name.
right-brace 4096 Use of \} where a number was expected.
scale 32 Meaningless scaling indicators.
space 65536 Missing space between a request or macro and its argument. This warning will be given when an undefined name longer than two characters is encountered, and the first two characters of the name make a defined name. The request or macro will not be invoked. When this warning is given, no macro is automatically defined. This is enabled by default. This warning will never occur in compatibility mode.
syntax 128 Dubious syntax in numeric expressions.
tab 2048 Inappropriate use of a tab character. Either use of a tab character where a number was expected, or use of tab character in an unquoted macro argument.

There are also names that can be used to refer to groups of warnings:

all All warnings except di, mac, and reg. It is intended that this covers all warnings that are useful with traditional macro packages.
w All warnings.

Environment

troff makes use of the following environment variables:

GROFF_TMAC_PATH A colon-separated list of directories in which to search for macro files. troff will scan directories given in the -M option before these, and in standard directories (current directory if in unsafe mode, home directory, /usr/lib/groff/site-tmac, /usr/share/groff/site-tmac, /usr/share/groff/1.22.2/tmac) after these.
GROFF_TYPESETTER Default device.
GROFF_FONT_PATH A colon separated list of directories in which to search for the devname directory. troff will scan directories given in the -F option before these, and in standard directories (/usr/share/groff/site-font, /usr/share/groff/1.22.2/font, /usr/lib/font) after these.

Files

/usr/share/groff/1.22.2/tmac/troffrc Initialization file (called before any other macro package).
/usr/share/groff/1.22.2/tmac/troffrc-end Initialization file (called after any other macro package).
/usr/share/groff/1.22.2/tmac/name.tmac, /usr/share/groff/1.22.2/tmac/tmac.name Macro files
/usr/share/groff/1.22.2/font/devname/DESC Device description file for device name.
/usr/share/groff/1.22.2/font/devname/F Font file for font F of device name.

Note that troffrc and troffrc-end are neither searched in the current nor in the home directory by default for security reasons (even if the -U option is given). Use the -M command line option or the GROFF_TMAC_PATH environment variable to add these directories to the search path if necessary.

troff examples

troff myfile

Process file myfile.

checknr — Check nroff and troff files for errors.
col — Filter reverse linefeeds.
dpost — Translate files created by troff into PostScript under Solaris.
eqn — Language processor for describing equations.
lp — Print a file on the System V operating system.
man — Display the manual page of a given command.
nroff — Format documents for terminal display or line-printer.
tbl — Preprocessor which formats tables for nroff or troff.