# JavaScript Shell

The JavaScript shell provides a simple way to run scripts in batch mode or an interactive environment for exploratory programming.

## Invoking the Shell

`java org.mozilla.javascript.tools.shell.Main [options] script-filename-or-url [script-arguments]`

where `options` are:

`-e script-source`

> Executes script-source as a JavaScript script.

`-f script-filename-or-url`

> Reads script-filename-or-url content and execute it as a JavaScript script.

`-opt optLevel`
`-O optLevel`

Optimizes at level optLevel, which must be an integer between 0 and 9. See Optimization for more details.

`-version versionNumber`

Specifies the language version to compile with. The string versionNumber must be one of `100`, `110`, `120`, `130`, or `140`. See JavaScript Language Versions for more information on language versions.

If the shell is invoked with the system property rhino.use_java_policy_security set to true and with a security manager installed, the shell restricts scripts permissions based on their URLs according to Java policy settings. This is available only if JVM implements Java2 security model.

## Predefined Properties

Scripts executing in the shell have access to some additional properties of the top-level object.

#### arguments

> The `arguments` object is an array containing the strings of all the arguments given at the command line when the shell was invoked.

#### help()

> Executing the help function will print usage and help messages.

#### defineClass(className)

> Define an extension using the Java class named with the string argument className. Uses ScriptableObject.defineClass() to define the extension.

#### deserialize(filename)

> Restore from the specified file an object previously written by a call to `serialize`.

#### load([filename, ...])

> Load JavaScript source files named by string arguments. If multiple arguments are given, each file is read in and executed in turn.

#### loadClass(className)

> Load and execute the class named by the string argument className. The class must be a class that implements the Script interface, as will any script compiled by jsc.

#### print([expr ...])

> Evaluate and print expressions. Evaluates each expression, converts the result to a string, and prints it.

#### readFile(path [, characterCoding)

> Read given file and convert its bytes to a string using the specified character coding or default character coding if explicit coding argument is not given.

#### readUrl(url [, characterCoding)

> Open an input connection to the given string url, read all its bytes and convert them to a string using the specified character coding or default character coding if explicit coding argument is not given.

#### runCommand(commandName, [arg, ...] [options])

> Execute the specified command with the given argument and options as a separate process and return the exit status of the process. For details, see JavaDoc for org.mozilla.javascript.tools.shell.Global#runCommand.

#### serialize(object, filename)

> Serialize the given object to the specified file.

#### spawn(functionOrScript)

> Run the given function or script in a different thread.

#### sync(function)

> creates a synchronized function (in the sense of a Java synchronized method) from an existing function. The new function synchronizes on the `this` object of its invocation.

#### quit()

> Quit shell. The shell will also quit in interactive mode if an end-of-file character is typed at the prompt.

#### version([number])

> Get or set JavaScript version number. If no argument is supplied, the current version number is returned. If an argument is supplied, it is expected to be one of `100`, `110`, `120`, `130,` or `140` to indicate JavaScript version 1.0, 1.1, 1.2, 1.3, or 1.4 respectively.

## Example

#### Invocation

Here the shell is invoked three times from the command line. (The system command prompt is shown as `$`.) The first invocation executes a script specified on the command line itself. The next invocation has no arguments, so the shell goes into interactive mode, reading and evaluating each line as it is typed in. Finally, the last invocation executes a script from a file and accesses arguments to the script itself.

    $ java org.mozilla.javascript.tools.shell.Main -e print('hi')
    hi
    $ java org.mozilla.javascript.tools.shell.Main
    js> print('hi')
    hi
    js> 6*7
    42
    js> function f() {
    	return a;
    }
    js> var a = 34;
    js> f()
    34
    js> quit()
    $ cat echo.js
    for (i in arguments) {
    	print(arguments[i])
    }
    $ java org.mozilla.javascript.tools.shell.Main echo.js foo bar
    foo
    bar
    $

#### spawn and sync

The following example creates 2 threads via `spawn` and uses `sync` to create a synchronized version of the function `test`.

    js> function test(x) {
    	print("entry");
    	java.lang.Thread.sleep(x*1000);
    	print("exit");
    }
    js> var o = { f : sync(test) };
    js> spawn(function() {o.f(5);});
    Thread[Thread-0,5,main]
    entry
    js> spawn(function() {o.f(5);});
    Thread[Thread-1,5,main]
    js>
    exit
    entry
    exit

#### runCommand

Here is few examples of invoking `runCommand` under Linux.

    js> runCommand('date')
    Thu Jan 23 16:49:36 CET 2003
    0
    // Using input option to provide process input
    js> runCommand("sort", {input: "c\na\nb"})
    a
    b
    c
    0
    js> // Demo of output and err options
    js> var opt={input: "c\na\nb", output: 'Sort Output:\n'}
    js> runCommand("sort", opt)
    0
    js> print(opt.output)
    Sort Output:
    a
    b
    c
    js> var opt={input: "c\na\nb", output: 'Sort Output:\n', err: ''}
    js> runCommand("sort", "--bad-arg", opt)
    2
    js> print(opt.err)
    /bin/sort: unrecognized option `--bad-arg'
    Try `/bin/sort --help' for more information.

    js> runCommand("bad_command", "--bad-arg", opt)
    js: "", line 18: uncaught JavaScript exception: java.io.IOException: bad_command: not found
    js> // Passing explicit environment to the system shell
    js> runCommand("sh", "-c", "echo $env1 $env2", { env: {env1: 100, env2: 200}})
    100 200
    0
    js> // Use args option to provide additional command arguments
    js> var arg_array = [1, 2, 3, 4];
    js> runCommand("echo", { args: arg_array})
    1 2 3 4
    0

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