PIC(1)                                                                  PIC(1)



NAME
       pic - compile pictures for troff or TeX

SYNOPSIS
       pic [-nvCSU] [filename ...]
       pic -t [-cvzCSU] [filename ...]

DESCRIPTION
       This manual page describes the GNU version of pic, which is part of the
       groff document formatting system.  pic compiles descriptions of
       pictures embedded within troff or TeX input files into commands that
       are understood by TeX or troff. Each picture starts with a line
       beginning with .PS and ends with a line beginning with .PE. Anything
       outside of .PS and .PE is passed through without change.

       It is the user's responsibility to provide appropriate definitions of
       the PS and PE macros.  When the macro package being used does not
       supply such definitions (for example, old versions of -ms), appropriate
       definitions can be obtained with -mpic: these will center each picture.

OPTIONS
       Options that do not take arguments may be grouped behind a single -.
       The special option -- can be used to mark the end of the options.  A
       filename of - refers to the standard input.

       -C     Recognize .PS and .PE even when followed by a character other
              than space or newline.

       -S     Safer mode; do not execute sh commands.  This can be useful when
              operating on untrustworthy input.  (enabled by default)

       -U     Unsafe mode; revert the default option -S.

       -n     Don't use the groff extensions to the troff drawing commands.
              You should use this if you are using a postprocessor that
              doesn't support these extensions.  The extensions are described
              in groff_out(5). The -n option also causes pic not to use
              zero-length lines to draw dots in troff mode.

       -t     TeX mode.

       -c     Be more compatible with tpic. Implies -t. Lines beginning with \
              are not passed through transparently.  Lines beginning with. are
              passed through with the initial. changed to \. A line beginning
              with .ps is given special treatment: it takes an optional
              integer argument specifying the line thickness (pen size) in
              milliinches; a missing argument restores the previous line
              thickness; the default line thickness is 8 milliinches.  The
              line thickness thus specified takes effect only when a
              non-negative line thickness has not been specified by use of the
              thickness attribute or by setting the linethick variable.

       -v     Print the version number.

       -z     In TeX mode draw dots using zero-length lines.

       The following options supported by other versions of pic are ignored:

       -D     Draw all lines using the \D escape sequence.  pic always does
              this.

       -T dev Generate output for the troff device dev. This is unnecessary
              because the troff output generated by pic is device-independent.

USAGE
       This section describes only the differences between GNU pic and the
       original version of pic.  Many of these differences also apply to newer
       versions of Unix pic.

   TeX mode
       TeX mode is enabled by the -t option.  In TeX mode, pic will define a
       vbox called \graph for each picture.  You must yourself print that vbox
       using, for example, the command
              \centerline{\box\graph}

       Actually, since the vbox has a height of zero this will produce
       slightly more vertical space above the picture than below it;
              \centerline{\raise 1em\box\graph}

       would avoid this.

       You must use a TeX driver that supports the tpic specials, version 2.

       Lines beginning with \ are passed through transparently; a % is added
       to the end of the line to avoid unwanted spaces.  You can safely use
       this feature to change fonts or to change the value of \baselineskip.
       Anything else may well produce undesirable results; use at your own
       risk.  Lines beginning with a period are not given any special
       treatment.

   Commands
       for variable = expr1 to expr2 [by [*]expr3] do X body X
              Set variable to expr1. While the value of variable is less than
              or equal to expr2, do body and increment variable by expr3; if
              by is not given, increment variable by 1.  If expr3 is prefixed
              by * then variable will instead be multiplied by expr3. X can be
              any character not occurring in body.

       if expr then X if-true X [else Y if-false Y]
              Evaluate expr; if it is non-zero then do if-true, otherwise do
              if-false. X can be any character not occurring in if-true. Y can
              be any character not occurring in if-false.

       print arg...
              Concatenate the arguments and print as a line on stderr.  Each
              arg must be an expression, a position, or text.  This is useful
              for debugging.

       command arg...
              Concatenate the arguments and pass them through as a line to
              troff orTeX.  Each arg must be an expression, a position, or
              text.  This has a similar effect to a line beginning with. or \,
              but allows the values of variables to be passed through.

       sh X command X
              Pass command to a shell.  X can be any character not occurring
              in command.

       copy "filename"
              Include filename at this point in the file.

       copy ["filename"] thru X body X [until "word"]
              

       copy ["filename"] thru macro [until "word"]
              This construct does body once for each line of filename; the
              line is split into blank-delimited words, and occurrences of $i
              in body, for i between 1 and 9, are replaced by the i-th word of
              the line.  If filename is not given, lines are taken from the
              current input up to .PE. If an until clause is specified, lines
              will be read only until a line the first word of which is word;
              that line will then be discarded.  X can be any character not
              occurring in body. For example,

                     
                     .PS
                     copy thru % circle at ($1,$2) % until "END"
                     1 2
                     3 4
                     5 6
                     END
                     box
                     .PE


              is equivalent to

                     
                     .PS
                     circle at (1,2)
                     circle at (3,4)
                     circle at (5,6)
                     box
                     .PE


              The commands to be performed for each line can also be taken
              from a macro defined earlier by giving the name of the macro as
              the argument to thru.

       reset

       reset variable1, variable2 ...
              Reset pre-defined variables variable1, variable2 ... to their
              default values.  If no arguments are given, reset all
              pre-defined variables to their default values.  Note that
              assigning a value to scale also causes all pre-defined variables
              that control dimensions to be reset to their default values
              times the new value of scale.

       plot expr ["text"]
              This is a text object which is constructed by using text as a
              format string for sprintf with an argument of expr. If text is
              omitted a format string of s%gs is used.  Attributes can be
              specified in the same way as for a normal text object.  Be very
              careful that you specify an appropriate format string; pic does
              only very limited checking of the string.  This is deprecated in
              favour of sprintf.

       variable:=expr
              This is similar to = except variable must already be defined,
              and the value of variable will be changed only in the innermost
              block in which it is defined.  (By contrast, = defines the
              variable in the current block if it is not already defined
              there, and then changes the value in the current block.)

       Arguments of the form


              X anything X

       are also allowed to be of the form


              { anything }

       In this case anything can contain balanced occurrences of { and }.
       Strings may contain X or imbalanced occurrences of { and }.

   Expressions
       The syntax for expressions has been significantly extended:

       x ^ y (exponentiation)
       sin(x)
       cos(x)
       atan2(y, x)
       log(x) (base 10)
       exp(x) (base 10, ie 10x)
       sqrt(x)
       int(x)
       rand() (return a random number between 0 and 1)
       rand(x) (return a random number between 1 and x; deprecated)
       max(e1, e2)
       min(e1, e2)
       !e
       e1 && e2
       e1 || e2
       e1 == e2
       e1 != e2
       e1 >= e2
       e1 > e2
       e1 <= e2
       e1 < e2
       "str1" == "str2"
       "str1" != "str2"

       String comparison expressions must be parenthesised in some contexts to
       avoid ambiguity.

   Other Changes
       A bare expression, expr, is acceptable as an attribute; it is
       equivalent to dir expr, where dir is the current direction.  For
       example


              line 2i

       means draw a line 2 inches long in the current direction.

       The maximum width and height of the picture are taken from the
       variables maxpswid and maxpsht. Initially these have values 8.5 and 11.

       Scientific notation is allowed for numbers.  For example
              x = 5e-2

       Text attributes can be compounded.  For example,
              "foo" above ljust
       is legal.

       There is no limit to the depth to which blocks can be examined.  For
       example,
              [A: [B: [C: box ]]] with .A.B.C.sw at 1,2
              circle at last [].A.B.C
       is acceptable.

       Arcs now have compass points determined by the circle of which the arc
       is a part.

       Circles and arcs can be dotted or dashed.  In TeX mode splines can be
       dotted or dashed.

       Boxes can have rounded corners.  The rad attribute specifies the radius
       of the quarter-circles at each corner.  If no rad or diam attribute is
       given, a radius of boxrad is used.  Initially, boxrad has a value of 0.
       A box with rounded corners can be dotted or dashed.

       The .PS line can have a second argument specifying a maximum height for
       the picture.  If the width of zero is specified the width will be
       ignored in computing the scaling factor for the picture.  Note that GNU
       pic will always scale a picture by the same amount vertically as
       horizontally.  This is different from the DWB 2.0 pic which may scale a
       picture by a different amount vertically than horizontally if a height
       is specified.

       Each text object has an invisible box associated with it.  The compass
       points of a text object are determined by this box.  The implicit
       motion associated with the object is also determined by this box.  The
       dimensions of this box are taken from the width and height attributes;
       if the width attribute is not supplied then the width will be taken to
       be textwid; if the height attribute is not supplied then the height
       will be taken to be the number of text strings associated with the
       object times textht. Initially textwid and textht have a value of 0.

       In places where a quoted text string can be used, an expression of the
       form


              sprintf(sformats, arg,...)

       can also be used; this will produce the arguments formatted according
       to format, which should be a string as described in printf(3)
       appropriate for the number of arguments supplied, using only the e, f,
       g or % format characters.

       The thickness of the lines used to draw objects is controlled by the
       linethick variable.  This gives the thickness of lines in points.  A
       negative value means use the default thickness: in TeX output mode,
       this means use a thickness of 8 milliinches; in TeX output mode with
       the -c option, this means use the line thickness specified by .ps
       lines; in troff output mode, this means use a thickness proportional to
       the pointsize.  A zero value means draw the thinnest possible line
       supported by the output device.  Initially it has a value of -1.  There
       is also a thick[ness] attribute.  For example,
              circle thickness 1.5

       would draw a circle using a line with a thickness of 1.5 points.  The
       thickness of lines is not affected by the value of the scale variable,
       nor by the width or height given in the .PS line.

       Boxes (including boxes with rounded corners), circles and ellipses can
       be filled by giving then an attribute of fill[ed]. This takes an
       optional argument of an expression with a value between 0 and 1; 0 will
       fill it with white, 1 with black, values in between with a
       proportionally gray shade.  A value greater than 1 can also be used:
       this means fill with the shade of gray that is currently being used for
       text and lines.  Normally this will be black, but output devices may
       provide a mechanism for changing this.  Without an argument, then the
       value of the variable fillval will be used.  Initially this has a value
       of 0.5.  The invisible attribute does not affect the filling of
       objects.  Any text associated with a filled object will be added after
       the object has been filled, so that the text will not be obscured by
       the filling.

       Arrow heads will be drawn as solid triangles if the variable arrowhead
       is non-zero and either TeX mode is enabled or the -x option has been
       given.  Initially arrowhead has a value of 1.

       The troff output of pic is device-independent.  The -T option is
       therefore redundant.  All numbers are taken to be in inches; numbers
       are never interpreted to be in troff machine units.

       Objects can have an aligned attribute.  This will only work when the
       postprocessor is grops. Any text associated with an object having the
       aligned attribute will be rotated about the center of the object so
       that it is aligned in the direction from the start point to the end
       point of the object.  Note that this attribute will have no effect for
       objects whose start and end points are coincident.

       In places where nth is allowed `expr'th is also allowed.  Note that 'th
       is a single token: no space is allowed between the ' and the th. For
       example,


              
              for i = 1 to 4 do {
                 line from `i'th box.nw to `i+1'th box.se
              }

FILES
       /usr/local/share/tmac/tmac.pic
              Example definitions of the PS and PE macros.

SEE ALSO
       troff(1), groff_out(5), tex(1)
       Tpic: Pic for TeX
       Brian W. Kernighan, PIC -- A Graphics Language for Typesetting (User
       Manual).  AT&T Bell Laboratories, Computing Science Technical Report
       No. 116 <URL:http://cm.bell-labs.com/cm/cs/cstr/116.ps.gz> (revised
       May, 1991).

BUGS
       Input characters that are illegal for groff (ie those with ASCII code 0
       or between 013 and 037 octal or between 0200 and 0237 octal) are
       rejected even in TeX mode.

       The interpretation of fillval is incompatible with the pic in 10th
       edition Unix, which interprets 0 as black and 1 as white.



Groff Version 1.15                                                9 April 2000
