Install Ghostview

apt install gv
gv test.ps -watch
# adjust view settings: `1.000 > Fit to Window`

Postscript is Stack-based

% some multiplications
5 3 mul 5 mul

put 5 on the stack
- stack: [5]
put 3 on the stack
- stack: [5 3]
multiply top two elements on stack and put on the stack
- stack: [15]
put 5 on the stack
- stack: [15 5]
multiply top two elements on stack and put on the stack
- stack: [15 5 mul] -> [75]

Functions and Variables

Functions look like this:

/[func_name] {[function operations]} def

For example, to create a function which converts from inches to pixel coordinates (72 pixels per inch)

% function to convert inches to pixels
/inch {72 mul} def

Then to use the function

3 inch 3 inch mul

put 3 on the stack
- stack: [3]
put {72 mul} on the stack
- stack: [3 72 mul] -> [216]
put 3 on the stack
- stack: [216 3]
put {72 mul} on the stack
- stack: [216 3 72 mul] -> [216 216]
multiply top two elements on stack and put on the stack
- stack: [216 216 mul] -> [46656]

Postscript makes no distinction between variables and functions

% braces are optional for single argument
/some_constant 123 def
/some_constant {123} def

Moving and Drawing Lines

Postscript uses a coordinate system from the bottom-left of the page:

   +y

   ^
   |
   |
   |
   o----> +x

/inch {72 mul} def

3 inch 3 inch moveto
% this is equivalent to '216 216 moveto'

% draw a square
3 inch 0 inch rlineto  % bottom edge
0 inch 3 inch rlineto  % right edge
3 inch 0 inch rlineto  % top edge
0 inch -3 inch rlineto % left edge

% draw the stroked out path
stroke

We can also rotate the entire canvas to draw a square

/inch {72 mul} def

3 inch 3 inch moveto
% this is equivalent to '216 216 moveto'

% draw a square
3 inch 0 inch rlineto
90 rotate
3 inch 0 inch rlineto
90 rotate
3 inch 0 inch rlineto
90 rotate
3 inch 0 inch rlineto
90 rotate

% draw the stroked out path
stroke

Use the repeat command to perform repeated actions

/inch {72 mul} def

3 inch 3 inch moveto
% this is equivalent to '216 216 moveto'

% draw a square
4 {
3 inch 0 inch rlineto
90 rotate
} repeat

% we can also fill the square if we close the path first
closepath
fill

% draw the stroked out path
stroke

Writing Text

/inch {72 mul} def

/Times-Roman findfont
30 scalefont         % set font size
setfont              % set the font to times new roman

3 inch 3 inch moveto
(Hello world!) show

Sending Postscript data to printer

Lots of networked printers are listening on TCP 9100 for data to print. Most accept Postscript directly (and even PDF!).

$ nc [printer_address] 9100 < test.ps

Append a showpage as the last line to tell the printer to begin printing:

% some cool postscript stuff
% ...

showpage

Other Dumb Printer Things

Printers also accept PJL commands, which can control printers jobs:

echo "@PJL ECHO INSERT TOKEN" | nc [printer_address] 9100

echo '@PJL RDYMSG DISPLAY="Insert Coin"' | nc [printer_address] 9100

More Resources

Pretty graphics: https://pianomanfrazier.com/post/drawing-with-postscript/

More postscript examples from me: https://github.com/Evidlo/examples/tree/master/postscript

Summary of other commands: https://personal.math.ubc.ca/~cass/courses/ps.html

Evidlo/postscript