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pic(1)                     General Commands Manual                    pic(1)

Name         top

       pic - compile pictures for troff or TeX

Synopsis         top

       pic [-nvCSU] [file ...]

       pic -t [-cvzCSU] [file ...]

Description         top

       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         top

       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

       -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-

Usage         top

       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 file


   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 document:

                 \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 example,

                     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, i.e. 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

       Boxes can have slanted sides.  This effectively changes the shape of
       a box from a rectangle to an arbitrary parallelogram.  The xslanted
       and yslanted attributes specify the x and y offset of the box's upper
       right corner from its default position.

       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.  Only the flags
       ‘#’, ‘-’, ‘+’, and ‘ ’ (space), a minimum field width, an optional
       precision, and the conversion specifications %e, %E, %f, %g, %G, and
       %% are supported.

       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 or slanted sides),
       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, or gropdf.  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

Conversion         top

       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® 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.

       An alternative may be to use the -Tpdf option to convert your picture
       directly into PDF format.  The MediaBox of the file produced can be
       controlled by passing a -P-p papersize to groff.

       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.

Files         top

              Example definitions of the PS and PE macros.

See Also         top

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

       Eric S. Raymond, Making Pictures With GNU PIC.
       /usr/local/share/doc/groff-1.22.4/pic.ps (this file, together with
       its source file, pic.ms, is part of the groff documentation)

       Tpic: Pic for TeX

       Brian W. Kernighan, PIC — A Graphics Language for Typesetting (User
       Manual)http://cm.bell-labs.com/cm/cs/cstr/116.ps.gz⟩.  AT&T Bell
       Laboratories, Computing Science Technical Report No. 116 (revised
       May, 1991).

       ps2eps is available from CTAN mirrors, e.g., 

       W. Richard Stevens, Turning PIC into HTMLhttp://www.kohala.com/start/troff/pic2html.html⟩

       W. Richard Stevens, Examples of pic Macroshttp://www.kohala.com/start/troff/pic.examples.ps

Bugs         top

       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® is a registered trademark of Adobe Systems Incorporation.

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 2020-08-13.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-08-12.)  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            16 May 2020                          pic(1)

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