Chapters:
1: Introduction
2: Simple example
3: Invocation
4: Finer Control
5: X-Y Plots
6: Contour Plots
7: Image Plots
8: Examples
9: Gri Commands
10: Programming
11: Environment
12: Emacs Mode
13: History
14: Installation
15: Gri Bugs
16: Test Suite
17: Gri in Press
18: Acknowledgments
19: License
Indices:
Concepts
Commands
Variables

## 9.2: Command syntax

The syntax description is enclosed within angled single quotes, optional items are enclosed in square brackets, multiword items are enclosed in curly braces, and vertical bars separate different legitimate choices. For example, the documentation item for the command for drawing contours

    `draw contour \
        [.value. |  \
          {.min. .max. .inc. [.inc_unlabelled.]}] \
        [unlabelled]'

indicates that following are legal:

    draw contour                   # gri selects levels
    draw contour unlabelled        # " but unlabelled
    draw contour 10                # single contour line
    draw contour 10 unlabelled     # " but unlabelled
    draw contour 0 100 10          # contours at z=0,1,
    draw contour 0 10 1 unlabelled # " but unlabelled
    # contours at 0, 0.1, ... labelled at 0, 1
    draw contour 0 10 1 0.1

Note that items enclosed in braces must appear in their entirety; for example,

    draw contour 0 10              # WRONG; missing .inc.

which might look similar ``draw contour .min. .max. .inc.`' to you, looks like garbage to Gri. Gri will recognize it as an attempt at the ``draw contour`' command (because the first 2 words match the syntax) but it will then get confused, spit out an error message, and quit.