Updated: 2022/Sep/29

Please read Privacy Policy. It's for your privacy.

PIC(1)                      General Commands Manual                     PIC(1)

       pic - compile pictures for troff or TeX

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

       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 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

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

       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.  A complete documentation is available in the


   TeX mode
       TeX mode is enabled by the -t option.  In TeX mode, pic will define a
       vbox called \graph for each picture.  Use the figname command to change
       the name of the vbox.  You must yourself print that vbox using, for
       example, the command


       Actually, since the vbox has a height of zero (it is defined with
       \vtop) this will produce slightly more vertical space above the picture
       than below it;

              \centerline{\raise 1em\box\graph}

       would avoid this.

       To make the vbox having a positive height and a depth of zero (as used
       e.g. by LaTeX's graphics.sty), define the following macro in your

                 \vbox{\unvbox\csname #1\endcsname\kern 0pt}}

       Now you can simply say \gpicbox{graph} instead of \box\graph.

       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

       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.  The
              value of expr3 can be negative for the additive case; variable
              is then tested whether it is greater than or equal to expr2.
              For the multiplicative case, expr3 must be greater than zero.
              If the constraints aren't met, the loop isn't executed.  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 or TeX.  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.  For

                     x = 14
                     command ".ds string x is " x "."


                     x is 14.

       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,

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

              is equivalent to

                     circle at (1,2)
                     circle at (3,4)
                     circle at (5,6)

              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 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 "%g" 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 expr will be assigned to variable without creating a
              variable local to the current block.  (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 only.)
              For example, the following:

                     x = 3
                     y = 3
                       x := 5
                       y = 5
                     print x " " y


                     5 3

       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 }.

       The syntax for expressions has been significantly extended:

       x ^ y (exponentiation)
       atan2(y, x)
       log(x) (base 10)
       exp(x) (base 10, ie 10^x)
       rand() (return a random number between 0 and 1)
       rand(x) (return a random number between 1 and x; deprecated)
       srand(x) (set the random number seed)
       max(e1, e2)
       min(e1, e2)
       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

              line 2i

       means draw a line 2 inches long in the current direction.  The `i' (or
       `I') character is ignored; to use another measurement unit, set the
       scale variable to an appropriate value.

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

       Scientific notation is allowed for numbers.  For example

              x = 5e-2

       Text attributes can be compounded.  For example,

              "foo" above ljust

       is valid.

       There is no limit to the depth to which blocks can be examined.  For

              [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, ellipses, and arcs can be dotted or dashed.  In TeX mode
       splines can be dotted or dashed also.

       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 well
       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 (almost all) places where a quoted text string can be used, an
       expression of the form

              sprintf("format", 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.

       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 them 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.

       Three additional modifiers are available to specify colored objects:
       outline[d] sets the color of the outline, shaded the fill color, and
       colo[u]r[ed] sets both.  All three keywords expect a suffix specifying
       the color, for example

              circle shaded "green" outline "black"

       Currently, color support isn't available in TeX mode.  Predefined color
       names for groff are in the device macro files, for example ps.tmac;
       additional colors can be defined with the .defcolor request (see the
       manual page of troff(1) for more details).

       To change the name of the vbox in TeX mode, set the pseudo-variable
       figname (which is actually a specially parsed command) within a
       picture.  Example:

              figname = foobar;

       The picture is then available in the box \foobar.

       pic assumes that at the beginning of a picture both glyph and fill
       color are set to the default value.

       Arrow heads will be drawn as solid triangles if the variable arrowhead
       is non-zero and either TeX mode is enabled or the -n option has not
       been given.  Initially arrowhead has a value of 1.  Note that solid
       arrow heads are always filled with the current outline color.

       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 if 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

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

       To obtain a stand-alone picture from a pic file, enclose your pic code
       with .PS and .PE requests; roff configuration commands may be added at
       the beginning of the file, but no roff text.

       It is necessary to feed this file into groff without adding any page
       information, so you must check which .PS and .PE requests are actually
       called.  For example, the mm macro package adds a page number, which is
       very annoying.  At the moment, calling standard groff without any macro
       package works.  Alternatively, you can define your own requests, e.g.
       to do nothing:

              .de PS
              .de PE

       groff itself does not provide direct conversion into other graphics
       file formats.  But there are lots of possibilities if you first
       transform your picture into PostScript(R) format using the groff option
       -Tps.  Since this ps-file lacks BoundingBox information it is not very
       useful by itself, but it may be fed into other conversion programs,
       usually named ps2other or pstoother or the like.  Moreover, the
       PostScript interpreter ghostscript (gs) has built-in graphics
       conversion devices that are called with the option

              gs -sDEVICE=<devname>


              gs --help

       for a list of the available devices.

       As the Encapsulated PostScript File Format EPS is getting more and more
       important, and the conversion wasn't regarded trivial in the past you
       might be interested to know that there is a conversion tool named
       ps2eps which does the right job.  It is much better than the tool
       ps2epsi packaged with gs.

       For bitmapped graphic formats, you should use pstopnm; the resulting
       (intermediate) PNM file can be then converted to virtually any graphics
       format using the tools of the netpbm package .

              Example definitions of the PS and PE macros.

       troff(1), groff_out(5), tex(1), gs(1), ps2eps(1), pstopnm(1),
       ps2epsi(1), pnm(5)

       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 <http://cm.bell-labs.com/cm/cs/cstr/116.ps.gz> (revised May,

       ps2eps is available from CTAN mirrors, e.g.

       W. Richard Stevens - Turning PIC Into HTML

       W. Richard Stevens - Examples of picMacros

       Input characters that are invalid for groff (i.e., those with ASCII
       code 0, or 013 octal, or between 015 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.

       PostScript(R) is a registered trademark of Adobe Systems Incorporation.

Groff Version 1.19.2           September 4, 2005                        PIC(1)