troff(1) — Linux manual page

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troff(1)                 General Commands Manual                troff(1)

Name         top

       troff - GNU roff typesetter and document formatter

Synopsis         top

       troff [-abcCEiRUz] [-d ctext] [-d string=text] [-f font-family]
             [-F font-directory] [-I inclusion-directory] [-m macro-
             package] [-M macro-directory] [-n page-number] [-o page-
             list] [-r cnumeric-expression] [-r register=numeric-
             expression] [-T output-device] [-w warning-category]
             [-W warning-category] [file ...]

       troff --help

       troff -v
       troff --version

Description         top

       GNU troff transforms groff(7) language input into the device-
       independent output format described in groff_out(5); troff is
       thus the heart of the GNU roff document formatting system.  If no
       file operands are present, or if file is “-”, troff reads the
       standard input stream.

       GNU troff is functionally compatible with the AT&T troff
       typesetter and features numerous extensions.  Many people prefer
       to use the groff(1) command, a front end which also runs
       preprocessors and output drivers in the appropriate order and
       with appropriate options.

Options         top

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

       -a     Generate a plain text approximation of the typeset output.
              The read-only register .A is set to 1.  This option
              produces a sort of abstract preview of the formatted
              output.

              •  Page breaks are marked by a phrase in angle brackets;
                 for example, “<beginning of page>”.

              •  Lines are broken where they would be in formatted
                 output.

              •  Vertical motion, apart from that implied by a break, is
                 not represented.

              •  A horizontal motion of any size is represented as one
                 space.  Adjacent horizontal motions are not combined.
                 Inter-sentence space nodes (those arising from the
                 second argument to the .ss request) are not
                 represented.

              •  A special character is rendered as its identifier
                 between angle brackets; for example, a hyphen appears
                 as “<hy>”.

              The above description should not be considered a
              specification; the details of -a output are subject to
              change.

       -b     Write a backtrace reporting the state of troff's input
              parser to the standard error stream with each diagnostic
              message.  The line numbers given in the backtrace might
              not always be correct, because troff's idea of line
              numbers can be confused by requests that append to macros.

       -c     Start with color output disabled.

       -C     Enable AT&T troff compatibility mode; implies -c.  See
              groff_diff(7).

       -d ctext
       -d string=text
              Define roff string c or string as text.  c must be a one-
              character identifier; string can be of arbitrary length.
              Such assignments happen before any macro file is loaded,
              including the startup file.  Due to getopt_long(3)
              limitations, c cannot be, and string cannot contain, an
              equals sign, even though that is a valid character in a
              roff identifier.

       -E     Inhibit troff error messages; implies -Ww.  This option
              does not suppress messages sent to the standard error
              stream by documents or macro packages using tm or related
              requests.

       -f fam Use fam as the default font family.

       -F dir Search in directory dir for the selected output device's
              directory of device and font description files.  See the
              description of GROFF_FONT_PATH in section “Environment”
              below for the default search locations and ordering.

       -i     Read the standard input stream after all named input files
              have been processed.

       -I dir Search the directory dir for files (those named on the
              command line; in psbb, so, and soquiet requests; and in
              “\X'ps: import'”, “\X'ps: file'”, and “\X'pdf: pdfpic'”
              device control escape sequences).  -I may be specified
              more than once; each dir is searched in the given order.
              To search the current working directory before others, add
              “-I .” at the desired place; it is otherwise searched
              last.  -I works similarly to, and is named for, the
              “include” option of Unix C compilers.

       -m mac Search for the macro package mac.tmac and read it prior to
              any input files.  If not found, tmac.mac is attempted.
              See the description of GROFF_TMAC_PATH in section
              “Environment” below for the default search locations and
              ordering.

       -M dir Search directory dir for macro files.  See the description
              of GROFF_TMAC_PATH in section “Environment” below for the
              default search locations and ordering.

       -n num Begin numbering pages at num.  The default is 1.

       -o list
              Output only pages in list, which is a comma-separated list
              of inclusive page ranges; n means page n, m-n means every
              page between m and n, -n means every page up to n, and n-
              means every page from n on.  troff stops processing and
              exits after formatting the last page enumerated in list.

       -r cnumeric-expression
       -r register=numeric-expression
              Define roff register c or register as numeric-expression.
              c must be a one-character identifier; register can be of
              arbitrary length.  Such assignments happen before any
              macro file is loaded, including the startup file.  Due to
              getopt_long(3) limitations, c cannot be, and register
              cannot contain, an equals sign, even though that is a
              valid character in a roff identifier.

       -R     Don't load troffrc and troffrc-end.

       -T dev Prepare output for device dev.  The default is ps; see
              groff(1).

       -U     Operate in unsafe mode, enabling the open, opena, pi, pso,
              and sy requests, which are disabled by default because
              they allow an untrusted input document to write to
              arbitrary file names and run arbitrary commands.  This
              option also adds the current directory to the macro
              package search path; see the -m and -M options above.

       -w cat
       -W cat Enable and inhibit, respectively, warnings in category
              cat.  See section “Warnings” below.

       -z     Suppress formatted output.

Warnings         top

       Warning diagnostics emitted by troff are divided into named,
       numbered categories.  The name associated with each warning
       category is used by the -w and -W options.  Each category is also
       assigned a power of two; the sum of enabled category codes is
       used by the warn request and the .warn register.  Warnings of
       each category are produced under the following circumstances.

           ┌───────────────────────┬─────────────────────────────┐
           │ Bit   Code   Category │ Bit    Code      Category   │
           ├───────────────────────┼─────────────────────────────┤
           │   0      1   char     │  10      1024   reg         │
           │   1      2   number   │  11      2048   tab         │
           │   2      4   break    │  12      4096   right-brace │
           │   3      8   delim    │  13      8192   missing     │
           │   4     16   el       │  14     16384   input       │
           │   5     32   scale    │  15     32768   escape      │
           │   6     64   range    │  16     65536   space       │
           │   7    128   syntax   │  17    131072   font        │
           │   8    256   di       │  18    262144   ig          │
           │   9    512   mac      │  19    524288   color       │
           │                       │  20   1048576   file        │
           └───────────────────────┴─────────────────────────────┘

       break           4   A filled output line could not be broken such
                           that its length was less than the output line
                           length \n[.l].  This category is enabled by
                           default.

       char            1   No mounted font defines a glyph for the
                           requested character.  This category is
                           enabled by default.

       color      524288   An undefined color name was selected, an
                           attempt was made to define a color using an
                           unrecognized color space, an invalid
                           component in a color definition was
                           encountered, or an attempt was made to
                           redefine a default color.

       delim           8   The closing delimiter in an escape sequence
                           was missing or mismatched.

       di            256   A di, da, box, or boxa request was invoked
                           without an argument when there was no current
                           diversion.

       el             16   The el request was encountered with no prior
                           corresponding ie request.

       escape      32768   An unsupported escape sequence was
                           encountered.

       file      1048576   An attempt was made to load a file that does
                           not exist.  This category is enabled by
                           default.

       font       131072   A non-existent font was selected, or the
                           selection was ignored because a font
                           selection escape sequence was used after the
                           output line continuation escape sequence on
                           an input line.  This category is enabled by
                           default.

       ig         262144   An invalid escape sequence occurred in input
                           ignored using the ig request.  This warning
                           category diagnoses a condition that is an
                           error when it occurs in non-ignored input.

       input       16384   An invalid character occurred on the input
                           stream.

       mac           512   An undefined string, macro, or diversion was
                           used.  When such an object is dereferenced,
                           an empty one of that name is automatically
                           created.  So, unless it is later deleted, at
                           most one warning is given for each.

                           This warning is also emitted upon an attempt
                           to move an unplanted trap macro.  In such
                           cases, the unplanted macro is not
                           dereferenced, so it is not created if it does
                           not exist.

       missing      8192   A request was invoked with a mandatory
                           argument absent.

       number          2   An invalid numeric expression was
                           encountered.  This category is enabled by
                           default.

       range          64   A numeric expression was out of range for its
                           context.

       reg          1024   An undefined register was used.  When an
                           undefined register is dereferenced, it is
                           automatically defined with a value of 0.  So,
                           unless it is later deleted, at most one
                           warning is given for each.

       right-brace  4096   A right brace escape sequence \} was
                           encountered where a number was expected.

       scale          32   A scaling unit inappropriate to its context
                           was used in a numeric expression.

       space       65536   A space was missing between a request or
                           macro and its argument.  This warning is
                           produced when an undefined name longer than
                           two characters is encountered and the first
                           two characters of the name constitute a
                           defined name.  No request is invoked, no
                           macro called, and an empty macro is not
                           defined.  This category is enabled by
                           default.  It never occurs in compatibility
                           mode.

       syntax        128   A self-contradictory hyphenation mode was
                           requested; an empty or incomplete numeric
                           expression was encountered; an operand to a
                           numeric operator was missing; an attempt was
                           made to define a recursive, empty, or
                           nonsensical character class; or a groff
                           extension conditional expression operator was
                           used while in compatibility mode.

       tab          2048   A tab character was encountered where a
                           number was expected, or appeared in an
                           unquoted macro argument.

       Two warning names group other warning categories for convenience.

       all    All warning categories except di, mac, and reg.  This
              shorthand is intended to produce all warnings that are
              useful with macro packages and documents written for AT&T
              troff and its descendants, which have less fastidious
              diagnostics than GNU troff.

       w      All warning categories.  Authors of documents and macro
              packages targeting groff are encouraged to use this
              setting.

Environment         top

       GROFF_FONT_PATH and GROFF_TMAC_PATH each accept a search path of
       directories; that is, a list of directory names separated by the
       system's path component separator character.  On Unix systems,
       this character is a colon (:); on Windows systems, it is a
       semicolon (;).

       GROFF_FONT_PATH
              A list of directories in which to seek the selected output
              device's directory of device and font description files.
              troff will scan directories given as arguments to any
              specified -F options before these, then in a site-specific
              directory (/usr/local/share/groff/site-font), a standard
              location (/usr/local/share/groff/1.23.0/font), and a
              compatibility directory (/usr/lib/font) after them.

       GROFF_TMAC_PATH
              A list of directories in which to search for macro files.
              troff will scan directories given as arguments to any
              specified -M options before these, then the current
              directory (only if in unsafe mode), the user's home
              directory, a site-specific directory (/usr/local/share/
              groff/site-tmac), and a standard location (/usr/local/
              share/groff/1.23.0/tmac) after them.

       GROFF_TYPESETTER
              Set the default output device.  If empty or not set, ps is
              used.  The -T option overrides GROFF_TYPESETTER.

       SOURCE_DATE_EPOCH
              A timestamp (expressed as seconds since the Unix epoch) to
              use as the output creation timestamp in place of the
              current time.  The time is converted to human-readable
              form using gmtime(3) and asctime(3) when the formatter
              starts up and stored in registers usable by documents and
              macro packages.

       TZ     The time zone to use when converting the current time to
              human-readable form; see tzset(3).  If SOURCE_DATE_EPOCH
              is used, it is always converted to human-readable form
              using UTC.

Files         top

       /usr/local/share/groff/1.23.0/tmac/troffrc
              is an initialization macro file loaded before any macro
              packages specified with -m options.

       /usr/local/share/groff/1.23.0/tmac/troffrc-end
              is an initialization macro file loaded after all macro
              packages specified with -m options.

       /usr/local/share/groff/1.23.0/tmac/name.tmac
              are macro files distributed with groff.

       /usr/local/share/groff/1.23.0/font/devname/DESC
              describes the output device name.

       /usr/local/share/groff/1.23.0/font/devname/F
              describes the font F of device name.

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

Authors         top

       The GNU version of troff was originally written by James Clark;
       he also wrote the original version of this document, which was
       updated by Werner Lemberg ⟨wl@gnu.org⟩, Bernd Warken ⟨groff-bernd
       .warken-72@web.de⟩, and G. Branden Robinson ⟨g.branden.robinson@
       gmail.com⟩.

See also         top

       Groff: The GNU Implementation of troff, by Trent A. Fisher and
       Werner Lemberg, is the primary groff manual.  You can browse it
       interactively with “info groff”.

       groff(1)
              offers an overview of the GNU roff system and describes
              its front end executable.

       groff(7)
              details the groff language, including a short but complete
              reference of all predefined requests, registers, and
              escape sequences.

       groff_char(7)
              explains the syntax of groff special character escape
              sequences, and lists all special characters predefined by
              the language.

       groff_diff(7)
              enumerates the differences between AT&T device-independent
              troff and groff.

       groff_font(5)
              covers the format of groff device and font description
              files.

       groff_out(5)
              describes the format of troff's output.

       groff_tmac(5)
              includes information about macro files that ship with
              groff.

       roff(7)
              supplies background on roff systems in general, including
              pointers to further related documentation.

COLOPHON         top

       This page is part of the groff (GNU troff) project.  Information
       about the project can be found at 
       ⟨http://www.gnu.org/software/groff/⟩.  If you have a bug report
       for this manual page, see ⟨http://www.gnu.org/software/groff/⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://git.savannah.gnu.org/git/groff.git⟩ on 2023-12-22.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2023-12-08.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

groff 1.23.0.453-330f9-dirty 1 November 2023                    troff(1)

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