FESI Interperter

Free EcmaScript Interpreter.
A JavaScript interpreter written in Java.

The interactive interpreter

Calling the interpreter

The interpreter can run in batch mode and in interactive mode. A batch files has been created provided in the bin sub directory of the FESI installation. It can be edited to adapt the classpath or other parameters. Example:
java -DFESI.path=.;fesilib.jar -cp c:\program files\FESI\fesi.jar FESI.Interpreter.Interpret -f %1

The source files with extension "js", "es " and "esw" are recognized. As "js" is often used by Netscape or the Internet Explorer, this allows to bind "es" and "esw " to FESI.
The property FESI.path list the paths where the code is looked for load from the command line, by the load function (of BasicIO) and by the @module command.If it is absent, the java CLASSPATH is used instead. To obtain the same behaviour as before version 0.9-9, use "-DFESI.path=. " and use the option -f followed by a file name on the command line.

Batch mode

If started in batch mode (without the options -i), the interpreter reads and interprets the files specified in the command line and output the result to the standard output stream (with error to the standard error stream). If no file is specified on the command line, the standard input is read. The standard input can be specified by the "—" (two dashes) on the command line too. In both cases the standard input is read in batch mode (that is until an EOF is encountered, then interpreted). Any error will terminate the evaluation.

If the option -R className is specified, then the specified regular expression extension is loaded (otherwise FESI attempts to use the JDK text.util pacakge, the ORO pacakge or the GNU package, in that order.
If the option -e className is specified, the specified class is loaded as an extension.
If the option -f filename is specified, then the file is loaded (without searching in the path).
If the option -m modulename is specified, then the jar entry or file is loaded, searching in the path.
If the option -o filename is specified, the output is redirected to the specified file.
If the option -w is specified, error output is displayed via an AWT popup window, and BasicIOw is loaded instead of BasicIO ( for use with jrew and AWT based applications).
If the option -s is specified, error output is displayed via an Swing popup window, and BasicIOs is loaded instead of BasicIO ( for use with jrew and Swing based applications).
If the option -i is specified, an interactive read-eval-print loop is started (rather than a batch mode interpretation).
If the option -v display the version of FESI and of the environment even if not in interactive mode..
If the option -h filename is specified, the corresponding html file will be expanded (as with the @expand command). It is not looked in the path.
If the option -T filename is specified, the test file is processed (used for validation). It is not looked in the path.
If the option -D is specified, all tracing flags are turned on.
If the option -A ... is specified, all arguments after -A are passed in the args[] array of the evaluated program)

The option letters 'f', 'o', 'h', 'T' and 'A' must be the last ones of an option string (-wo is ok, -ow is not ok) because they must be immediately followed by their arguments.

Examples:

fesi preload.es -- postload.es -o result.lis

The above command will process preload.es, the standard input file and the postload.es, writing the result to result.lis. It could be attached to a specific extension under Windows.

The test mode (option -T) implements the special FESI command

@test nameOfTest

All the code which follows the @test command, until the next @test command or end of file, is interpreted in a special test mode. In that mode, the name of the @test is printed and the code is execute. Any error causes a message to be printed and the interpretation to skip to the next @test. If no error is detected, the result of the last statement is evaluated. If it is true the test is considered successful, otherwise an error message is printed.

Interactive mode

In interactive mode (option -i) first the file specified via -f or the -m are executed. Then files specified in the command line are loaded in the editor (Swing version only). Finally the system enter an interactive read-eval-print loop. Each statement is evaluated immediately when entered, and errors are not fatal. If a statement is incomplete, the interpreter requires more data (just enter ";" to force the end of a statement).

All batch mode options are allowed too, so it is possible to preload an environment before entering the interactive mode.

In addition the user can type the following commands:

`@exit`	Exit the interpreter
`@reset`	Reset the interpreter to a null environment (forgetting all loaded files too)
`@version`	Display version of interpreter
`@detail`	Return detail of last evaluation
`@extensions`	List loaded extensions (can be loaded with `loadExtension(class)` )
`@module`	Load the module in the directories and jar/zip files of the property FESI.path or (if the property is not defined) in the classpath (possibly adding the extension ".es", ".esw' or ".js").
`@load`	Load the files (possibly adding the extension ".es", ".esw' or ".js").
`@pwd`	Print current user directory
`@expand`	Expand an HTML file between `<script>` and `</script>` lines, display on standard output
`@help`	Display an short list of the allowed commands
`@about`	Display information on `FESI`
`@detail`	List the details of the last evaluation
`@list`	List the enumerated properties of the object (default to the global properties)
`@listall`	List all properties on an object (defaults to the global object)
`@describe`	Describe the detail characteristcis of an object, including java reflection data.
`@memory`	List the total and available memory (as reported by the Java runtime).
`@clear`	Clear the console window (but not the interpreter content). Usefull when reaching the limits of the console text area control.
`@path`	Display the current load path.

A couple of other commands are used to debug the interpreter or the access to the Java system, they are listed with the @help command. The commands can be abreviated to the first unambiguous prefix.
The interactive mode is useful to test short commands, or to load a file and then test its definitions.

If both the -i and -w options are given, an interactive window is used. Its implementation is very limited, and this is for use in operating systems with an even poorer native console interface only.

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Last update: 26 August 2003