PIC(1) MachTen Programmer’s Manual PIC(1)

NAME
pic - compile pictures for troff or TeX

SYNOPSIS
pic [ -nvC ] [ filename ... ]
pic -t [ -cvzC ] [ filename ... ]

DESCRIPTION
This manual page describes the GNU version of pic, which
is part of the groff document formatting system. pic com-
piles 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 pack-
age being used does not supply such definitions (for exam-
ple, 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 stan-
dard input.

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

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

-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 exten-
sions. 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 transpar-
ently. 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 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 dif-
ferences 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 calledgraph for each picture. You
must yourself print that vbox using, for example, the com-
mand

Actually, since the vbox has a height of zero this will
produce slightly more vertical space above the picture
than below it;

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 fontsb
or to change the value of aaselineskip. 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 incre-
ment variable by expr3; if by is not given, incre-
ment 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 posi-
tion, 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 simi-
lar 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 argu-
ment 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 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; depre-
cated)
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 direc-
tion. 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 speci-
fies 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 maxi-
mum height for the picture. If the width of zero is spec-
ified 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 horizon-
tally. This is different from the DWB 2.0 pic which may
scale a picture by a different amount vertically than hor-
izontally 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 sup-
plied 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("format", arg,...)

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

The thickness of the lines used to draw objects is con-
trolled by the linethick variable. This gives the thick-
ness 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 expres-
sion with a value between 0 and 1; 0 will fill it with
white, 1 with black, values in between with a proportion-
ally 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 fill-
ing 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 vari-
able 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 coin-
cident.

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/share/groff/tmac/tmac.pic
Example definitions of the PS and PE macros.

SEE ALSO
troff(1), groff_out(5), tex(1)
Tpic: Pic for TeX
AT&T Bell Laboratories, Computing Science Technical Report
No. 116, PIC -- A Graphics Language for Typesetting.
(This can be obtained by sending a mail message to
netlib@research.att.com with a body of
‘send 116 from research/cstr’.)

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 1.11 26 June 1995 7