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at:tutorial:iat [2008/07/01 16:23] – * tvcutsemat:tutorial:iat [2012/06/09 13:50] (current) – elisag
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 ====== Interactive AmbientTalk ====== ====== Interactive AmbientTalk ======
 +
  
 ===== Basic Usage ===== ===== Basic Usage =====
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 </code> </code>
  
-To start ''iat'', it suffices to execute it from the command-line, provided the ''java'' executable of a JDK1.3.3 or higher JVM is on your executable search path.+To start ''iat'', it suffices to execute it from the command-line, provided the ''java'' executable of a JDK1.3.3 or higher JVM is on your executable search path. The shell script that starts ''iat'' works as follows: 
 + 
 +<code> 
 +iat [options] [file] [arguments] 
 +</code>
  
 Perhaps the most useful usage of ''iat'' is to start it with an AmbientTalk source file as argument, e.g.: Perhaps the most useful usage of ''iat'' is to start it with an AmbientTalk source file as argument, e.g.:
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 This will make ''iat'' evaluate all of the contents of the file ''foo.at'' and print out the value of the last expression in the file. If ''-p'' was not specified on the command line, ''iat'' falls into a read-eval-print loop such that you can play around with the definitions loaded from the file. Any arguments following the filename are treated as arguments to the AmbientTalk program, not to ''iat''. They are accessible by evaluating ''system.getArgv()''. This will make ''iat'' evaluate all of the contents of the file ''foo.at'' and print out the value of the last expression in the file. If ''-p'' was not specified on the command line, ''iat'' falls into a read-eval-print loop such that you can play around with the definitions loaded from the file. Any arguments following the filename are treated as arguments to the AmbientTalk program, not to ''iat''. They are accessible by evaluating ''system.getArgv()''.
  
-<note tip> +To get an overview of all available options, execute: 
-If you started ''iat'' in a directory that contains the file ''foo.at'', you can also load the file from within the read-eval-print loop by evaluating ''~.foo''. Once the file is loaded, evaluating ''~.foo'' again won't load the file twice, and there is currently no way to "unload" the file. The exact meaning of ''~.foo'' will become clear later, in [[at:tutorial:modular#namespaces_and_the_lobby|the chapter on modular programming]].+ 
 +<code> 
 +iat --help 
 +</code> 
 + 
 +<note> 
 +An explanation of all the iat command line parameters is available [[http://code.google.com/p/ambienttalk/wiki/CommandLineParameters|here]].
 </note> </note>
  
-===== Command-line Parameters =====+===== Shell Commands =====
  
-To get an overview of all available options, execute:+The AmbientTalk shell understands a limited number of "shell commands". All input starting with a colon (":") is treated by ''iat'' as a shell command. The following commands are supported: 
 +  * '':q'' or '':quit'' => quit the interpreter. 
 +  * '':l'' or '':load filepath'' => load a file (relative to the directory in which ''iat'' was invoked). The content of the file is evaluated as if the file was passed as argument to the shell during startup. The public definitions of the loaded file will be available at top-level. 
 + 
 +===== Input and Output ===== 
 + 
 +The AmbientTalk shell enables very simple input and output operations by means of the top-level ''system'' object. Here is how to output text to the command-line:
  
 <code> <code>
-iat --help+system.println("Hello world");
 </code> </code>
  
-The most important options are explained below: +Reading a line of text from the command-line is a bit less straightforward: 
-  * ''-i, --init init-file'': you can replace the intialisation code file that AmbientTalk uses to initialize the lexical root of each actor, which defaults to ''at/init/init.at''. This is useful for defining your own "language extensions". + 
-  * ''-o, --objectpath objectpath'': the **object path** is for AmbientTalk what the class path is for Java. However, unlike Java's class path, which lists the locations of available Classes, the object path consists of ''name=directory'' pairs, separated by the system path separator ('':'' on *NIX/mac, '';'' on windows). For each such pair, a slot named ''name'' is added to the global ''lobby'' object, bound to a namespace pointing to the given directory. Hence, evaluating ''lobby.name.foo'' in AmbientTalk enables access to the file ''directory/foo.at''. Thanks to the object path, AmbientTalk programs remain free of absolute path names when loading other AmbientTalk files. +<code> 
-  * ''-n, --network name'': allows you to specify the name of the AmbientTalk overlay network to join. Only AmbientTalk VMs started using the same name will be discoverable and will be able to discover this VM. This is primarily useful for debugging or demo purposes, if you don't want other programs to interfere.+system.readNextLine: { |line| 
 +  system.println("I read: "+line) 
 +} catch: { |ioException| /* ignored */ } 
 +</code> 
 + 
 +The code between ''{'' and ''}'' basically serves as a callback function which will be invoked when the next line has been read. The reason for this callback-style read function is that AmbientTalk code may never be blocking. The rationale behind this execution model is explained later, in the [[actors|chapter on actors]]. 
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