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pic(1)                   General Commands Manual                  pic(1)

Name         top

       pic - compile pictures for troff or TeX

Synopsis         top

       pic [-nCSU] [file ...]

       pic -t [-czCSU] [file ...]

       pic --help

       pic -v
       pic --version

Description         top

       The GNU implementation of pic is part of the groff(1) document
       formatting system.  pic is a troff(1) preprocessor that compiles
       descriptions of diagrammatic pictures embedded in troff or TeX
       input files into the language understood by TeX or troff.  It
       copies the contents of each file to the standard output stream,
       except that lines between .PS and either .PE or .PF are
       interpreted as picture descriptions.  Ending a pic picture with
       .PE leaves the page position at the bottom of the picture; ending
       it with .PF leaves the position at the top.  Normally, pic is not
       executed directly by the user, but invoked by specifying the -p
       option to groff(1).  If no file operands are given on the command
       line, or if file is “-”, the standard input stream is read.

       It is the user's responsibility to provide appropriate
       definitions of the PS, PE, and PF 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

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

       -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

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

       -n     Don't use 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.

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

       -t     TeX mode.

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

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

       The following options supported by other versions of pic are

       -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

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 tpic version 2 specials.
       (tpic was a fork of AT&T pic by Tim Morgan of the University of
       California at Irvine that diverged from its source around 1984.
       It is best known today for lending its name to a group of
       \special commands it produced for TeX.)

       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.

       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 the
              standard error stream.  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.
              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

       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

                     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 11.

       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 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, 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.

       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.  GNU pic will always scale a picture by the same amount
       vertically as well as horizontally.  This is different from 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 “ ” [sp]ace), 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, as shown below.

              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.  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(1) or gropdf(1).  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.  This
       attribute will have no effect on objects whose start and end
       points are coincident.

       In places where nth is allowed, 'exprth' is also allowed.  “'th“
       is a single token: no space is allowed between the apostrophe 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(1)) 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(5) file can be then converted to
       virtually any graphics format using the tools of the netpbm

Files         top

              Example definitions of the PS, PE, and PF macros.

Bugs         top

       Characters that are invalid as input to GNU troff (see the groff
       Texinfo manual or groff_char(7) for a list) are rejected even in
       TeX mode.

       The interpretation of fillval is incompatible with the pic in
       Tenth Edition Research Unix, which interprets 0 as black and 1 as

See also         top

              “Making Pictures with GNU pic”, by Eric S. Raymond.  This
              file, together with its source, pic.ms, is part of the
              groff distribution.

       “PIC—A Graphics Language for Typesetting: User Manual”, by Brian
       W. Kernighan, 1991, AT&T Bell Laboratories Computing Science
       Technical Report No. 116

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

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 2021-08-27.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2021-08-23.)  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

groff 1.23.0.rc1.654-4e1db-dir1t9yAugust 2021                       pic(1)

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