TROFF(1)                                                 TROFF(1)

NAME
       troff - format documents

SYNOPSIS
       troff [ -abivzCER ] [ -wname ] [ -Wname ] [ -dcs ]
             [ -ffam ] [ -mname ] [ -nnum ] [ -olist ] [ -rcn ]
             [ -Tname ] [ -Fdir ] [ -Mdir ] [ files... ]

DESCRIPTION
       This manual page describes the GNU version of troff, which
       is part of the groff document formatting  system.   It  is
       highly  compatible  with Unix troff.  Usually it should be
       invoked using the groff command, which will also run  pre-
       processors and postprocessors in the appropriate order and
       with the appropriate options.

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 correct: troff's
                 idea  of  line numbers gets confused by as or am
                 requests.

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

       -v        Print the version number.

       -wname    Enable  warning  name.   Available  warnings are
                 described  in  the  Warnings  subsection  below.
                 Multiple -w options are allowed.

       -Wname    Inhibit  warning  name.  Multiple -W options are
                 allowed.

       -E        Inhibit all error messages.

       -z        Suppress formatted output.

       -C        Enable compatibility mode.

       -dcs
       -dname=s  Define c or name to be a string s; c must  be  a
                 one letter name.

       -ffam     Use fam as the default font family.

       -mname    Read  in the file tmac.name.  Normally this will
                 be searched for in /usr/lib/groff/tmac.

       -R        Don't load troffrc.

       -nnum     Number the first page num.

       -olist    Output only pages in list, which is a comma-sep-
                 arated  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.

       -Tname    Prepare  output for device name, rather than the
                 default ps.

       -Fdir     Search dir for subdirectories devname  (name  is
                 the  name  of  the device) for the DESC file and
                 font      files      before      the      normal
                 /usr/lib/groff/font.

       -Mdir     Search  directory dir for macro files before the
                 normal /usr/lib/groff/tmac.

USAGE
       Only the features not in Unix troff are described here.

   Long names
       The     names     of     number     registers,      fonts,
       strings/macros/diversions,  special  characters  can be of
       any length. In escape sequences, where you can use (xx for
       a  two  character  name,  you  can use [xxx] for a name of
       arbitrary length:

       \[xxx] Print the special character called xxx.

       \f[xxx]
              Set font xxx.

       \*[xxx]
              Interpolate string xxx.

       \n[xxx]
              Interpolate number register xxx.

   Fractional pointsizes
       A scaled point  is  equal  to  1/sizescale  points,  where
       sizescale  is  specified  in the DESC file (1 by default.)
       There is a new scale indicator z which has the  effect  of
       multiplying  by  sizescale.  Requests and escape sequences
       in troff interpret arguments that represent a pointsize as
       being  in  units  of scaled points, but they evaluate each
       such argument using a default scale indicator of z.  Argu-
       ments  treated  in  this  way  are  the argument to the ps
       request, the third argument to the cs request, the  second
       and  fourth  arguments to the tkf request, the argument to
       the \H escape sequence,  and  those  variants  of  the  \s
       escape  sequence  that  take a numeric expression as their
       argument.

       For example, suppose sizescale  is  1000;  then  a  scaled
       point  will be equivalent to a millipoint; the request .ps
       10.25 is equivalent to .ps 10.25z and so sets  the  point-
       size  to  10250  scaled  points,  which  is equal to 10.25
       points.

       The number register \n(.s returns the pointsize in  points
       as  decimal fraction.  There is also a new number register
       \n[.ps] that returns the pointsize in scaled points.

       It would make no sense to use the z scale indicator  in  a
       numeric  expression whose default scale indicator was nei-
       ther u nor z, and so troff disallows this.   Similarly  it
       would  make no sense to use a scaling indicator other than
       z or u in a numeric expression whose default scale indica-
       tor was z, and so troff disallows this as well.

       There  is  also  new scale indicator s which multiplies by
       the number of units in a scaled point.  So,  for  example,
       \n[.ps]s is equal to 1m.  Be sure not to confuse the s and
       z scale indicators.

   Numeric expressions
       Spaces are permitted in a number expression within  paren-
       theses.

       M indicates a scale of 100ths of an em.

       e1>?e2 The maximum of e1 and e2.

       e1<?e2 The minimum of e1 and e2.

       (c;e)  Evaluate  e  using c as the default scaling indica-
              tor.  If c is missing, ignore scaling indicators in
              the evaluation of e.

   New escape sequences
       \A'anything'
              This  expands to 1 or 0 according as anything is or
              is not acceptable as the name of a  string,  macro,
              diversion,  number  register,  environment or font.
              It will return 0 if anything  is  empty.   This  is
              useful  if  you  want  to lookup user input in some
              sort of associative table.

       \C'xxx'
              Typeset character named xxx.  Normally it  is  more
              convenient to use \[xxx].  But \C has the advantage
              that it is compatible with recent versions of  UNIX
              and is available in compatibility mode.

       \E     This is equivalent to an escape character, but it's
              not interpreted in copy-mode.  For example, strings
              to  start  and  end superscripting could be defined
              like this:

                     .ds { \v'-.3m'\s'\En[.s]*6u/10u'
                     .ds } \s0\v'.3m'

              The use of \E ensures that these  definitions  will
              work even if \*{ gets interpreted in copy-mode (for
              example, by being used in a macro argument.)

       \N'n'  Typeset the character with code n  in  the  current
              font.   n  can  be  any integer.  Most devices only
              have characters with codes between 0 and  255.   If
              the  current font does not contain a character with
              that code, special fonts will not be searched.  The
              \N escape sequence can be conveniently used on con-
              junction with the char request:

                     .char \[phone] \f(ZD\N'37'

              The code of each character is given in  the  fourth
              column  in  the  font  description  file  after the
              charset command.  It is possible to include unnamed
              characters  in the font description file by using a
              name of ---; the \N escape sequence is the only way
              to use these.

       \R'name +-n'
              This has the same effect as

                     .nr name +-n

       \s(nn
       \s+-(nn
              Set the point size to nn points; nn must be exactly
              two digits.

       \s[+-n]
       \s+-[n]
       \s'+-n'
       \s+-'n'
              Set the point size to  n  scaled  points;  n  is  a
              numeric  expression  with a default scale indicator
              of z.

       \Vx
       \V(xx
       \V[xxx]
              Interpolate the contents of the  environment  vari-
              able  xxx , as returned by getenv(3).  \V is inter-
              preted in copy-mode.

       \Yx
       \Y(xx
       \Y[xxx]
              This is approximately  equivalent  to  \X'\*[xxx]'.
              However the contents of the string or macro xxx are
              not interpreted; also it is permitted  for  xxx  to
              have  been defined as a macro and thus contain new-
              lines (it is not permitted for the argument  to  \X
              to  contain  newlines).   The inclusion of newlines
              requires an extension to the Unix troff output for-
              mat,  and  will  confuse  drivers  that do not know
              about this extension.

       \Z'anything'
              Print anything and then restore the horizontal  and
              vertical position; anything may not contain tabs or
              leaders.

       \$0    The name by which the current  macro  was  invoked.
              The als request can make a macro have more than one
              name.

       \$*    In a macro, the concatenation of all the  arguments
              separated by spaces.

       \$@    In  a macro, the concatenation of all the arguments
              with each surrounded by double  quotes,  and  sepa-
              rated by spaces.

       \$(nn
       \$[nnn]
              In  a  macro,  this gives the nn-th or nnn-th argu-
              ment.  Macros can have a unlimited number of  argu-
              ments.

       \?anything\?
              When  used  in a diversion, this will transparently
              embed anything in the diversion.  anything is  read
              in  copy  mode.  When the diversion is reread, any-
              thing will be interpreted.  anything may  not  con-
              tain  newlines;  use  \!  if you want to embed new-
              lines in a diversion.  The escape sequence  \?   is
              also recognised in copy mode and turned into a sin-
              gle internal code; it is this code that  terminates
              anything.  Thus
                     .nr x 1
                     .nf
                     .di d
                     \?\\?\\\\?\\\\\\\\nx\\\\?\\?\?
                     .di
                     .nr x 2
                     .di e
                     .d
                     .di
                     .nr x 3
                     .di f
                     .e
                     .di
                     .nr x 4
                     .f

              will print 4.

       \/     This increases the width of the preceding character
              so that the spacing between that character and  the
              following  character will be correct if the follow-
              ing character is a roman character.   For  example,
              if  an  italic f is immediately followed by a roman
              right parenthesis, then in many fonts the top right
              portion  of  the f will overlap the top left of the
              right parenthesis  producing  f),  which  is  ugly.
              Inserting  \/  produces f) and avoids this problem.
              It is a good idea to use this escape sequence when-
              ever an italic character is immediately followed by
              a roman character without any intervening space.

       \,     This modifies the spacing of the following  charac-
              ter  so that the spacing between that character and
              the preceding character will correct if the preced-
              ing  character  is a roman character.  For example,
              inserting \, between  the  parenthesis  and  the  f
              changes  (f  to  (f.  It is a good idea to use this
              escape sequence whenever a roman character is imme-
              diately followed by an italic character without any
              intervening space.

       \)     Like \& except that it  behaves  like  a  character
              declared  with the cflags request to be transparent
              for the purposes of end of sentence recognition.

       \~     This produces an unbreakable space  that  stretches
              like  a  normal  inter-word  space  when  a line is
              adjusted.

       \#     Everything up to and including the next newline  is
              ignored.   This  is interpreted in copy mode.  This
              is like \" except that \" does not ignore the  ter-
              minating newline.

   New requests
       .aln xx yy
              Create an alias xx for number register object named
              yy.  The new name and the old name will be  exactly
              equivalent.   If yy is undefined, a warning of type
              reg will be generated,  and  the  request  will  be
              ignored.

       .als xx yy
              Create  an  alias xx for request, string, macro, or
              diversion object named yy.  The new  name  and  the
              old  name will be exactly equivalent (it is similar
              to a hard rather than a soft link).  If yy is unde-
              fined, a warning of type mac will be generated, and
              the request will be ignored.  The de, am,  di,  da,
              ds, and as requests only create a new object if the
              name of the macro, diversion or string diversion is
              currently  undefined  or  if  it is defined to be a
              request; normally  they  modify  the  value  of  an
              existing object.

       .asciify xx
              This request only exists in order to make it possi-
              ble to make  certain  gross  hacks  work  with  GNU
              troff.   It  `unformats' the diversion xx in such a
              way that ASCII characters that were  formatted  and
              diverted  into  xx  will  be  treated like ordinary
              input characters when xx is reread.   For  example,
              this

                     .tr  @.
                     .di  x
                     @nr\  n\  1
                     .br
                     .di
                     .tr  @@
                     .asciify  x
                     .x

              will set register n to 1.

       .backtrace
              Print a backtrace of the input stack on stderr.

       .blm xx
              Set  the  blank  line  macro  to xx.  If there is a
              blank line macro, it will be invoked when  a  blank
              line  is  encountered  instead  of  the usual troff
              behaviour.

       .break Break out of a while loop.  See also the while  and
              continue  requests.   Be  sure  not to confuse this
              with the br request.

       .cflags n c1 c2...
              Characters c1, c2,...  have  properties  determined
              by n, which is ORed from the following:

              1      the   character  ends  sentences  (initially
                     characters .?!  have this property);

              2      lines can be  broken  before  the  character
                     (initially  no  characters  have  this prop-
                     erty); a line will not be broken at a  char-
                     acter  with this property unless the charac-
                     ters on each side both have non-zero hyphen-
                     ation codes.

              4      lines  can  be  broken  after  the character
                     (initially characters  -\(hy\(em  have  this
                     property);  a  line  will not be broken at a
                     character  with  this  property  unless  the
                     characters  on  each side both have non-zero
                     hyphenation codes.

              8      the character  overlaps  horizontally  (ini-
                     tially  characters  \(ul\(rn\(ru  have  this
                     property);

              16     the character overlaps vertically (initially
                     character \(br has this property);

              32     an end of sentence character followed by any
                     number of characters with this property will
                     be  treated as the end of a sentence if fol-
                     lowed by a newline or two spaces;  in  other
                     words  the  character is transparent for the
                     purposes of  end  of  sentence  recognition;
                     this is the same as having a zero space fac-
                     tor    in    TeX    (initially    characters
                     "')]*\(dg\(rq have this property).

       .char c string
              Define  character c to be string.  Every time char-
              acter c needs to be printed, string  will  be  pro-
              cessed  in  a  temporary environment and the result
              will be wrapped up into a single object.   Compati-
              bility mode will be turned off and the escape char-
              acter will be set to \ while string is  being  pro-
              cessed.  Any emboldening, constant spacing or track
              kerning will be applied to this object rather  than
              to  individual  characters  in string.  A character
              defined by this request can be  used  just  like  a
              normal character provided by the output device.  In
              particular other characters can be translated to it
              with  the  tr  request;  it  can be made the leader
              character by the lc request; repeated patterns  can
              be  drawn  with  the  character using the \l and \L
              escape sequences; words  containing  the  character
              can  be  hyphenated correctly, if the hcode request
              is used to give the character a  hyphenation  code.
              There  is  a special anti-recursion feature: use of
              character within the character's definition will be
              handled  like  normal  characters  not defined with
              char.  A character definition can be  removed  with
              the rchar request.

       .chop xx
              Chop  the  last  character  off  macro,  string, or
              diversion xx.  This is useful for removing the new-
              line  from  the  end  of  diversions that are to be
              interpolated as strings.

       .close stream
              Close the  stream  named  stream;  stream  will  no
              longer  be  an  acceptable  argument  to  the write
              request.  See the open request.

       .continue
              Finish the current iteration of a while loop.   See
              also the while and break requests.

       .cp n  If  n  is non-zero or missing, enable compatibility
              mode, otherwise disable it.  In compatibility mode,
              long  names  are not recognised, and the incompati-
              bilities caused by long names do not arise.

       .do xxx
              Interpret .xxx with  compatibility  mode  disabled.
              For example,

                     .do fam T

              would have the same effect as

                     .fam T

              except  that  it  would  work even if compatibility
              mode had been enabled.  Note that the previous com-
              patibility   mode  is  restored  before  any  files
              sourced by xxx are interpreted.

       .fam xx
              Set the current font family  to  xx.   The  current
              font  family  is  part  of the current environment.
              See the description of the  sty  request  for  more
              information on font families.

       .fspecial f s1 s2...
              When  the current font is f, fonts s1, s2,...  will
              be special, that is, they will searched for charac-
              ters  not in the current font.  Any fonts specified
              in the special request will be searched after fonts
              specified in the fspecial request.

       .ftr f g
              Translate  font f to g.  Whenever a font named f is
              referred to in \f escape sequence, or  in  the  ft,
              ul,  bd,  cs,  tkf,  special,  fspecial, fp, or sty
              requests, font g will be used.  If g is missing, or
              equal to f then font f will not be translated.

       .hcode c1 code1 c2 code2...
              Set  the  hyphenation code of character c1 to code1
              and that of c2 to code2.  A hyphenation  code  must
              be  a single input character (not a special charac-
              ter) other than a digit or a space.  Initially each
              lower-case  letter has a hyphenation code, which is
              itself, and each upper-case letter  has  a  hyphen-
              ation  code  which  is  the  lower  case version of
              itself.  See also the hpf request.

       .hla lang
              Set  the  current  hyphenation  language  to  lang.
              Hyphenation   exceptions   specified  with  the  hw
              request and hyphenation patterns specified with the
              hpf  request  are  both associated with the current
              hyphenation language.  The hla request  is  usually
              invoked by the troffrc file.

       .hlm n Set  the  maximum  number of consecutive hyphenated
              lines to n.  If n is negative, there is no maximum.
              The  default value is -1.  This value is associated
              with the current environment.   Only  lines  output
              from an environment count towards the maximum asso-
              ciated with that  environment.   Hyphens  resulting
              from \% are counted; explicit hyphens are not.

       .hpf file
              Read  hyphenation  patterns from file; this will be
              searched for in the  same  way  that  tmac.name  is
              searched  for  when the -mname option is specified.
              It should have the same format as the  argument  to
              the \patterns primitive in TeX; the letters appear-
              ing in this file  are  interpreted  as  hyphenation
              codes.   A  % character in the patterns file intro-
              duces a comment that continues to the  end  of  the
              line.   The  set of hyphenation patterns is associ-
              ated with the  current  language  set  by  the  hla
              request.  The hpf request is usually invoked by the
              troffrc file.

       .hym n Set the hyphenation margin to n: when  the  current
              adjustment  mode  is  not  b,  the line will not be
              hyphenated if the line is no  more  than  n  short.
              The  default  hyphenation margin is 0.  The default
              scaling indicator  for  this  request  is  m.   The
              hyphenation  margin  is associated with the current
              environment.  The  current  hyphenation  margin  is
              available in the \n[.hym] register.

       .hys n Set  the  hyphenation  space to n: when the current
              adjustment mode is b don't hyphenate  the  line  if
              the  line can be justified by adding no more than n
              extra  space  to  each  word  space.   The  default
              hyphenation  space is 0.  The default scaling indi-
              cator for this request is m.  The hyphenation space
              is  associated  with  the current environment.  The
              current  hyphenation  space  is  available  in  the
              \n[.hys] register.

       .kern n
              If  n is non-zero or missing, enable pairwise kern-
              ing, otherwise disable it.

       .mso file
              The same as the so  request  except  that  file  is
              searched  for  in  the  same  way that tmac.name is
              searched for when the -mname option is specified.

       .nroff Make the n built-in condition true and the t built-
              in condition false.  This can be reversed using the
              troff request.

       .open stream filename
              Open filename for writing and associate the  stream
              named stream with it.  See also the close and write
              requests.

       .opena stream filename
              Like open, but if filename  exists,  append  to  it
              instead of truncating it.

       .pnr   Print  the  names  and  contents  of  all currently
              defined number registers on stderr.

       .pso command
              This is behaves like the  so  request  except  that
              input comes from the standard output of command.

       .ptr   Print  the  names  and  positions of all traps (not
              including input line traps and diversion traps)  on
              stderr.   Empty  slots  in  the  page trap list are
              printed as well, because they can affect the prior-
              ity of subsequently planted traps.

       .rchar c1 c2...
              Remove  the  definitions  of  characters c1, c2,...
              This undoes the effect of a char request.

       .rj
       .rj n  Right justify the next n input lines.   Without  an
              argument  right  justify  the next input line.  The
              number of lines to be right justified is  available
              in  the  \n[.rj]  register.   This  implicitly does
              .ce 0.  The ce request implicitly does .rj 0.

       .rnn xx yy
              Rename number register xx to yy.

       .shc c Set the soft hyphen character to c.  If c is  omit-
              ted,  the  soft hyphen character will be set to the
              default \(hy.  The soft  hyphen  character  is  the
              character  which  will  be  inserted when a word is
              hyphenated at a line break.   If  the  soft  hyphen
              character does not exist in the font of the charac-
              ter immediately preceding a potential break  point,
              then  the  line  will  not be broken at that point.
              Neither  definitions  (specified  with   the   char
              request)  nor  translations  (specified with the tr
              request)  are  considered  when  finding  the  soft
              hyphen character.

       .shift n
              In  a  macro,  shift  the arguments by n positions:
              argument i becomes argument i-n; arguments 1  to  n
              will  no  longer  be  available.   If n is missing,
              arguments will be shifted by 1.  Shifting by  nega-
              tive amounts is currently undefined.

       .special s1 s2...
              Fonts  s1, s2, are special and will be searched for
              characters not in the current font.

       .sty n f
              Associate style f with font  position  n.   A  font
              position  can  be  associated either with a font or
              with a style.  The current font is the index  of  a
              font  position  and  so  is also either a font or a
              style.  When it is a style, the font that is  actu-
              ally used is the font the name of which is the con-
              catenation of the name of the  current  family  and
              the name of the current style.  For example, if the
              current font is 1 and font position 1 is associated
              with style R and the current font family is T, then
              font TR will be used.  If the current font is not a
              style,  then  the  current family is ignored.  When
              the requests cs,  bd,  tkf,  uf,  or  fspecial  are
              applied  to  a  style,  then  they  will instead be
              applied to the member of the current family  corre-
              sponding  to that style.  The default family can be
              set with the -f option.  The styles command in  the
              DESC  file  controls  which font positions (if any)
              are initially associated with  styles  rather  than
              fonts.

       .tkf f s1 n1 s2 n2
              Enable  track kerning for font f.  When the current
              font is f the width  of  every  character  will  be
              increased  by an amount between n1 and n2; when the
              current point size is less than or equal to s1  the
              width  will  be increased by n1; when it is greater
              than or equal to s2 the width will be increased  by
              n2; when the point size is greater than or equal to
              s1 and less than or equal to  s2  the  increase  in
              width is a linear function of the point size.

       .trf filename
              Transparently output the contents of file filename.
              Each line is output as it would be were it preceded
              by  \!; however, the lines are not subject to copy-
              mode interpretation.  If the file does not end with
              a newline, then a newline will be added.  For exam-
              ple, you can define a macro x containing  the  con-
              tents of file f, using

                     .di x
                     .trf f
                     .di

              Unlike with the cf request, the file cannot contain
              characters such as NUL that  are  not  legal  troff
              input characters.

       .trnt abcd
              This  is the same as the tr request except that the
              translations do not apply to text that is transpar-
              ently  throughput  into  a  diversion with \!.  For
              example,

              .tr ab
              .di x
              \!.tm a
              .di
              .x

              will print b; if trnt is used instead of tr it will
              print a.

       .troff Make  the  n  built-in  condition  false, and the t
              built-in condition true.  This undoes the effect of
              the nroff request.

       .vpt n Enable  vertical  position  traps if n is non-zero,
              disable them otherwise.   Vertical  position  traps
              are  traps set by the wh or dt requests.  Traps set
              by the it request are not vertical position  traps.
              The  parameter that controls whether vertical posi-
              tion traps are enabled is global.  Initially verti-
              cal position traps are enabled.

       .warn n
              Control  warnings.   n  is  the  sum of the numbers
              associated with each warning that is to be enabled;
              all  other  warnings  will be disabled.  The number
              associated with  each  warning  is  listed  in  the
              `Warnings' section.  For example, .warn 0 will dis-
              able all warnings, and .warn  1  will  disable  all
              warnings  except that about missing characters.  If
              n is not given, all warnings will be enabled.

       .while c anything
              While condition  c  is  true,  accept  anything  as
              input;  c  can be any condition acceptable to an if
              request; anything can comprise  multiple  lines  if
              the  first  line  starts  with \{ and the last line
              ends with \}.  See  also  the  break  and  continue
              requests.

       .write stream anything
              Write  anything to the stream named stream.  stream
              must previously have been the subject  of  an  open
              request.   anything is read in copy mode; a leading
              " will be stripped.

   Extended requests
       .cf filename
              When used in a diversion, this will  embed  in  the
              diversion  an object which, when reread, will cause
              the contents of filename to be transparently copied
              through to the output.  In Unix troff, the contents
              of filename is immediately copied  through  to  the
              output  regardless  of  whether  there is a current
              diversion; this behaviour is so anomalous  that  it
              must be considered a bug.

       .ev xx If  xx is not a number, this will switch to a named
              environment called xx.  The environment  should  be
              popped with a matching ev request without any argu-
              ments, just as for numbered environments.  There is
              no  limit on the number of named environments; they
              will be created the first time that they are refer-
              enced.

       .fp n f1 f2
              The  fp  request  has  an  optional third argument.
              This argument gives the external name of the  font,
              which  is  used  for  finding  the font description
              file.  The second argument gives the internal  name
              of  the  font which is used to refer to the font in
              troff after it has been mounted.  If  there  is  no
              third  argument then the internal name will be used
              as the external name.  This feature allows  you  to
              use fonts with long names in compatibility mode.

       .ss m n
              When two arguments are given to the ss request, the
              second argument gives the sentence space size.   If
              the  second  argument  is  not  given, the sentence
              space size will be the same as the word space size.
              Like  the word space size, the sentence space is in
              units of one twelfth of  the  spacewidth  parameter
              for  the  current  font.   Initially  both the word
              space size and the sentence space size are 12.  The
              sentence  space  size is used in two circumstances:
              if the end of a sentence occurs at  the  end  of  a
              line  in  fill  mode, then both an inter-word space
              and a sentence space will be added; if  two  spaces
              follow  the  end  of  a sentence in the middle of a
              line, then the second  space  will  be  a  sentence
              space.   Note that the behaviour of Unix troff will
              be exactly that exhibited by GNU troff if a  second
              argument  is never given to the ss request.  In GNU
              troff, as in Unix troff, you should always follow a
              sentence with either a newline or two spaces.

       .ta n1 n2...nn T r1 r2...rn
              Set  tabs  at positions n1, n2,..., nn and then set
              tabs  at  nn+r1,  nn+r2,....,  nn+rn  and  then  at
              nn+rn+r1,  nn+rn+r2,...,  nn+rn+rn, and so on.  For
              example,

                     .ta T .5i

              will set tabs every half an inch.

   New number registers
       The following read-only registers are available:

       \n[.C] 1 if compatibility mode is in effect, 0  otherwise.

       \n[.cdp]
              The  depth  of the last character added to the cur-
              rent environment.  It is positive if the  character
              extends below the baseline.

       \n[.ce]
              The  number  of  lines remaining to be centered, as
              set by the ce request.

       \n[.cht]
              The height of the last character added to the  cur-
              rent  environment.  It is positive if the character
              extends above the baseline.

       \n[.csk]
              The skew of the last character added to the current
              environment.  The skew of a character is how far to
              the right of the center of a character  the  center
              of  an accent over that character should be placed.

       \n[.ev]
              The name or  number  of  the  current  environment.
              This is a string-valued register.

       \n[.fam]
              The  current  font family.  This is a string-valued
              register.

       \n[.fp]
              The number of the next free font position.

       \n[.g] Always 1.  Macros  should  use  this  to  determine
              whether they are running under GNU troff.

       \n[.hla]
              The  current hyphenation language as set by the hla
              request.

       \n[.hlc]
              The number  of  immediately  preceding  consecutive
              hyphenated lines.

       \n[.hlm]
              The  maximum  allowed number of consecutive hyphen-
              ated lines, as set by the hlm request.

       \n[.hy]
              The current hyphenation flags (as  set  by  the  hy
              request.)

       \n[.hym]
              The  current  hyphenation margin (as set by the hym
              request.)

       \n[.hys]
              The current hyphenation space (as set  by  the  hys
              request.)

       \n[.in]
              The indent that applies to the current output line.

       \n[.kern]
              1 if pairwise kerning is enabled, 0 otherwise.

       \n[.lg]
              The  current  ligature  mode  (as  set  by  the  lg
              request.)

       \n[.ll]
              The  line length that applies to the current output
              line.

       \n[.lt]
              The title length as set by the lt request.

       \n[.ne]
              The amount of space that was needed in the last  ne
              request that caused a trap to be sprung.  Useful in
              conjunction with the \n[.trunc] register.

       \n[.pn]
              The number of the next page: either the  value  set
              by  a pn request, or the number of the current page
              plus 1.

       \n[.ps]
              The current pointsize in scaled points.

       \n[.psr]
              The last-requested pointsize in scaled points.

       \n[.rj]
              The number of lines to be right-justified as set by
              the rj request.

       \n[.sr]
              The last requested pointsize in points as a decimal
              fraction.  This is a string-valued register.

       \n[.tabs]
              A string representation of the current tab settings
              suitable  for use as an argument to the ta request.

       \n[.trunc]
              The amount of vertical space truncated by the  most
              recently  sprung vertical position trap, or, if the
              trap was sprung by a ne request, minus  the  amount
              of  vertical motion produced by the ne request.  In
              other words, at the point a trap is sprung, it rep-
              resents  the  difference of what the vertical posi-
              tion would have been but for the trap, and what the
              vertical  position actually is.  Useful in conjunc-
              tion with the \n[.ne] register.

       \n[.ss]
       \n[.sss]
              These give the values of the parameters set by  the
              first and second arguments of the ss request.

       \n[.vpt]
              1  if vertical position traps are enabled, 0 other-
              wise.

       \n[.warn]
              The sum of the numbers associated with each of  the
              currently  enabled warnings.  The number associated
              with each warning is listed in the `Warnings'  sub-
              section.

       \n(.x  The major version number.  For example, if the ver-
              sion number is 1.03 then \n(.x will contain 1.

       \n(.y  The minor version number.  For example, if the ver-
              sion number is 1.03 then \n(.y will contain 03.

       The following registers are set by the \w escape sequence:

       \n[rst]
       \n[rsb]
              Like the st and sb registers, but takes account  of
              the heights and depths of characters.

       \n[ssc]
              The  amount of horizontal space (possibly negative)
              that should be added to the last character before a
              subscript.

       \n[skw]
              How  far to right of the center of the last charac-
              ter in the \w argument, the  center  of  an  accent
              from  a roman font should be placed over that char-
              acter.

       The following read/write number registers are available:

       \n[systat]
              The return value of the system() function  executed
              by the last sy request.

       \n[slimit]
              If greater than 0, the maximum number of objects on
              the input stack.  If less than or equal to 0, there
              is  no  limit on the number of objects on the input
              stack.  With no limit, recursion can continue until
              virtual memory is exhausted.

   Miscellaneous
       Fonts  not  listed  in  the  DESC  file  are automatically
       mounted on the next available font position when they  are
       referenced.   If  a  font is to be mounted explicitly with
       the fp request on an unused font position,  it  should  be
       mounted  on  the  first unused font position, which can be
       found in the \n[.fp] register;  although  troff  does  not
       enforce  this  strictly,  it  will  not allow a font to be
       mounted at a position whose number is  much  greater  than
       that of any currently used position.

       Interpolating  a string does not hide existing macro argu-
       ments.  Thus in a macro, a more efficient way of doing

              .xx \\$@

       is

              \\*[xx]\\

       If the font description  file  contains  pairwise  kerning
       information,  characters  from  that  font will be kerned.
       Kerning between two characters can be inhibited by placing
       a \& between them.

       In  a  string  comparison  in a condition, characters that
       appear at different input levels to  the  first  delimiter
       character  will  not  be recognised as the second or third
       delimiters.  This applies also to the tl request.  In a \w
       escape  sequence,  a character that appears at a different
       input level to the starting delimiter character  will  not
       be  recognised  as  the closing delimiter character.  When
       decoding a macro argument  that  is  delimited  by  double
       quotes,  a  character  that  appears  at a different input
       level to the starting  delimiter  character  will  not  be
       recognised as the closing delimiter character.  The imple-
       mentation of \$@ ensures that the double quotes  surround-
       ing  an  argument  will appear the same input level, which
       will be different to  the  input  level  of  the  argument
       itself.  In a long escape name ] will not be recognized as
       a closing delimiter except when  it  occurs  at  the  same
       input  level  as the opening ].  In compatibility mode, no
       attention is paid to the input-level.

       There are some new types of condition:

       .if rxxx
              True if there is a number register named xxx.

       .if dxxx
              True if there is a  string,  macro,  diversion,  or
              request named xxx.

       .if cch
              True  if  there  is a character ch available; ch is
              either an ASCII character or  a  special  character
              \(xx  or \[xxx]; the condition will also be true if
              ch has been defined by the char request.

   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.

       char           1   Non-existent   characters.    This   is
                          enabled by default.

       number         2   Invalid numeric expressions.   This  is
                          enabled by default.

       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.

       delim          8   Missing or  mismatched  closing  delim-
                          iters.

       el            16   Use  of the el request with no matching
                          ie request.

       scale         32   Meaningless scaling indicators.

       range         64   Out of range arguments.

       syntax       128   Dubious syntax in numeric  expressions.

       di           256   Use  of  di  or  da without an argument
                          when there is no current diversion.

       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.

       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.  a  defi-
                          nition  is  automatically  made  with a
                          value of 0.  So, in most cases, at most
                          one  warning will be given for use of a
                          particular name.

       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 argu-
                          ment.

       right-brace 4096   Use of \} where a number was  expected.

       missing     8192   Requests  that are missing non-optional
                          arguments.

       input      16384   Illegal input characters.

       escape     32768   Unrecognized escape sequences.  When an
                          unrecognized escape sequence is encoun-
                          tered, the escape character is ignored.

       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  encoun-
                          tered,  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.

       font      131072   Non-existent fonts.  This is enabled by
                          default.

       ig        262144   Illegal escapes in  text  ignored  with
                          the  ig  request.  These are conditions
                          that are errors when they do not  occur
                          in ignored text.

       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.

   Incompatibilities
       Long names cause some incompatibilities.  Unix troff  will
       interpret

              .dsabcd

       as  defining  a string ab with contents cd.  Normally, GNU
       troff will interpret this as  a  call  of  a  macro  named
       dsabcd.  Also Unix troff will interpret \*[ or \n[ as ref-
       erences to a string or number register called [.   In  GNU
       troff,  however,  this will normally be interpreted as the
       start of a long name.  In  compatibility  mode  GNU  troff
       will  interpret  these  things in the traditional way.  In
       compatibility mode, however, long  names  are  not  recog-
       nised.   Compatibility  mode  can be turned on with the -C
       command line option, and turned on  or  off  with  the  cp
       request.   The number register \n(.C is 1 if compatibility
       mode is on, 0 otherwise.

       GNU troff does not allow the use of the  escape  sequences
       \\|\^\&\}\{\(space)\'\`\-\_\!\%\c  in  names  of  strings,
       macros, diversions, number registers,  fonts  or  environ-
       ments;  Unix  troff  does.   The \A escape sequence may be
       helpful in avoiding  use  of  these  escape  sequences  in
       names.

       Fractional  pointsizes  cause one noteworthy incompatibil-
       ity.  In Unix troff the ps request ignores  scale  indica-
       tors and so

              .ps 10u

       will  set the pointsize to 10 points, whereas in GNU troff
       it will set the pointsize to 10 scaled points.

       In GNU troff there is  a  fundamental  difference  between
       unformatted, input characters, and formatted, output char-
       acters.  Everything that affects how an  output  character
       will  be output is stored with the character; once an out-
       put character has been constructed it is unaffected by any
       subsequent  requests  that are executed, including bd, cs,
       tkf, tr, or fp requests.  Normally output  characters  are
       constructed  from  input  characters at the moment immedi-
       ately before the character is added to the current  output
       line.   Macros,  diversions  and strings are all, in fact,
       the same type of object; they contain lists of input char-
       acters  and output characters in any combination.  An out-
       put character does not behave like an input character  for
       the  purposes of macro processing; it does not inherit any
       of the special properties that the  input  character  from
       which it was constructed might have had.  For example,

              .di x
              \\\\
              .br
              .di
              .x

       will  print  \\  in  GNU  troff;  each pair of input \s is
       turned into one output \ and the resulting output  \s  are
       not interpreted as escape characters when they are reread.
       Unix troff would interpret them as escape characters  when
       they  were  reread  and  would end up printing one \.  The
       correct way to obtain a printable  \  is  to  use  the  \e
       escape  sequence: this will always print a single instance
       of the current escape character, regardless of whether  or
       not  it  is used in a diversion; it will also work in both
       GNU troff and Unix troff.  If you wish for some reason  to
       store  in  a  diversion  an  escape  sequence that will be
       interpreted when the diversion is reread, you  can  either
       use  the  traditional \!  transparent output facility, or,
       if this is unsuitable, the new \?  escape sequence.

ENVIRONMENT
       GROFF_TMAC_PATH
              A colon separated list of directories in  which  to
              search for macro files.

       GROFF_TYPESETTER
              Default device.

       GROFF_FONT_PATH
              A  colon  separated list of directories in which to
              search  for  the  devname  directory.   troff  will
              search in directories given in the -F option before
              these,     and     in     standard      directories
              (.:/usr/lib/groff/font:/usr/lib/font)  after these.

FILES
       /usr/lib/groff/tmac/troffrc
              Initialization file

       /usr/lib/groff/tmac/tmac.name
              Macro files

       /usr/lib/groff/font/devname/DESC
              Device description file for device name.

       /usr/lib/groff/font/devname/F
              Font file for font F of device name.

SEE ALSO
       groff(1)  tbl(1),  pic(1),  eqn(1),  grops(1),  grodvi(1),
       grotty(1), groff_font(5), groff_out(5), groff_char(7)

Groff Version 1.11         26 June 1995                         1