| 8.2 Script Syntax | |
Let's look at the previous script in more detail:
SCRIPT tag
Vortex scripts start and end with <SCRIPT> tags denoting the language as Vortex.
Functions
Vortex script functions are declared with <A nbsp;NAME=name> tags, and end with matching </A> tags; declared function names are case-sensitive. When a script is run, the entry function is executed, which is by default main . All scripts must have a main function, so our example declares one. There are other types of functions, such as builtin and user functions, which we'll see later.
Statements
In this simple example we have no statements or function calls in main , but if we did they would closely follow HTML tag syntax. Any text in a function that is not recognized as a Vortex call is just printed out as-is. Thus our <BODY> tags and text are printed out.
Leading spaces are stripped from output lines. This allows Vortex code to be indented for readability, but saves the network bandwidth of sending lots of extra blank space. Any HTML comments in the script are also ignored and not printed out.
Variables
Variables are referenced with a dollar sign, so the variable $REMOTE_ADDR is printed out in this example. $REMOTE_ADDR indicates what address your browser is on; Vortex automatically sets this from the Web server's CGI environment. Variable names in Vortex are also case-sensitive.
Errors
Any errors - eg. bad syntax, table not found, etc. - are printed in HTML comments in the output. (They are also logged to the file /usr/local/morph3/texis/vortex.log , or c:\morph3\texis\vortex.log under Windows.) The comments keep the casual user from seeing the errors, yet allow programmers to easily see them in context by viewing the HTML source. (In non-HTML or compile mode, the comment tags are left out.) Our simple example produces no errors, but here's a hypothetical one:
015 /scripts/test:178: Variable expected in the function vx_parse
Error messages have a standard format that tells us something about the error. Each starts with a 3-digit code: numbers below 100 are errors, 100-199 are warnings, everything above is usually informational. Here 015 tells us this is a usage (15) error (less than 100). The script name and line number are given next, if applicable: this error happened on line 178 of /scripts/test . Then the message describing the error is given, possibly with the internal C function that it occurred in (this is useful for Thunderstone tech support).
Error messages are an important debugging tool. A script can catch some of its own error messages to recover from them on the fly; we'll cover that in the section on Dynamic nbsp;Error nbsp;Handling .
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