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

## 9.1: Overview of Gri Commands

The Gri commands may be divided roughly into a few categories, as indicated in the following list.

- Working with files: Commands are ``open`', ``close`', ``skip`', ``read`', and ``rewind`'.

- Controlling parameters of the drawn material: Various ``set`' commands control values of parameters, like size of plot, linewidth, font, etc.

- Drawing things: Various ``draw`' commands let you draw data, axes, etc.

- Interacting with the user: The ``query`' command gets instructions from the user. The ``show`' command displays messages to user.

- Controlling program flow: The ``if`' statement controls optional execution of commands (see If Statements). The ``while`' statement allows loops.

- Moving around in directories: The ``pwd`', ``cd`' and ``ls`' commands do the usual unix things.

- Using the operating system The ``system`' command passes instructions to the operating system; the output may be saved into a synonym by using ``\syn = system ...`'. The ``get env`' command determines the value of any unix environment variables the system has defined. For more discussion (see Operating System).

- Statistical operations: Some very limited capabilities exist; for example, ``regress`' does linear regression.

- Mathematical operations: Simple mathematical manipulation of column, grid, and image data is provided. Also, wherever Gri expects a number, it will accept a reverse-polish expression; for example, ``set x size 10`' could also be written ``set x size {rpn 20 2 /}`'. For details (see Mathematics).