8.5 How a Command Line is Processed

8.5 How a Command Line is

Processed

When FunnelWeb reads in a command line (from the console

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or a script file), it processes it in the following sequence:

Developer

The command line is checked for non printable

1.  

characters. If there are any, they are flagged with a severe

error.

Reference

1 Introduction

All dollar string substitution variables in the command

2.  

line are replaced by their corresponding string. The

2 Interface

command line is processed from left to right.

3 Scanner

Substitutions are performed non recursively.

4 Parser

At this point, if the line is empty, or consists entirely of

3.  

5 Analyser

blanks, it is ignored and the interpreter moves to the next

6 Tangle

line.

7 Weave

A severe error is generated if the line at this stage begins

4.  

8 Shell

with a blank.

9 Commands

If the first character of the line is "

5.  

!

", the line is a

10 Glossary

comment line and is ignored.

11 References

The run of non blanks commencing at the start of the line

6.  

is compared case insensitively to each of the legal

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command verbs. If the command is illegal, a severe error

is generated, otherwise the command is processed.

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Copyright   Ross N. Williams 1992,1999. All rights

reserved.

http://www.ross.net/funnelweb/reference/shell_processing.html [3/3/2000 10:46:13 PM]