
InteractiveExec |
util.InteractiveExec |
Execute a command as a separately running subprocess.
<p>This actor uses java.lang.Runtime.exec() to invoke a subprocess
named be the <i>command</i> parameter in a <i>directory</i> with an
<i>environment</i>. Data from the <i>input</i> port (if any) is
passed to the input of the subprocess. The subprocess is run until it
exits and then contents of the output and error streams of the
subprocess (if any) are passed to the <i>output</i> and <i>error</i>
ports.
<p>If the subprocess generates no data on the output or error stream,
then the data on the corresponding port(s) will consist of the empty string.
<p>A much more interesting actor could be written using a
Kahn Process Network. This actor would generate output asynchronously
as the process was executing.
<p>Currently, there appears to be no way to get the subprocess to
exit by passing it input. For example, if the <i>command</i> is set
to the <code>cat</code> command, and we pass in a Const with the
value <code>\04</code>, then the cat subprocess does <b>not</b> interpret
this as the end of file marker and exit.
<p>For information about Runtime.exec(), see:
<a href="http://jw.itworld.com/javaworld/jw-12-2000/jw-1229-traps.html" target="_top">http://jw.itworld.com/javaworld/jw-12-2000/jw-1229-traps.html</a>
and
<a href="http://mindprod.com/jgloss/exec.html" target="_top">http://mindprod.com/jgloss/exec.html</a>
Author(s): Christopher Hylands Brooks, Contributor: Edward A. Lee
Version:$Id: InteractiveExec.doc.html,v 1.1 2006/02/22 18:41:22 mangal Exp $
Pt.Proposed Rating:Yellow (cxh) 2/5/04
Pt.Accepted Rating:Yellow (cxh) 2/24/04
error
Data that is generated by the subprocess on its standard
error. While the process is running, any error data generated
by the subprocess is stored until the subprocess exits and
then the stored error data is sent to the <i>error</i> port.
If the subprocess generates no data on standard error, then
the empty string (a string of length zero) is generated.
<p>The port is an output port of type String.
input
Strings to pass to the standard input of the subprocess.
Note that a newline is not appended to the string. If you
require a newline, add one using the AddSubtract actor.
<p>This port is an input port of type String.
output
Data that is generated by the subprocess on standard out.
While the process is running, any output data generated
by the subprocess is stored until the subprocess exits and
then the stored output data is sent to the <i>output</i> port.
If the subprocess generates no data on standard out, then
the empty string (a string of length zero) is generated.
<p>The port is an output port of type String.
command
The command to be executed. The command is parsed by
<a href="../ptolemy/util/StringUtilities.html#tokenizeForExec">tokenizeForExec(String)</a>
into tokens and then executed as a separate subprocess.
The initial default value is the string
<code>echo "Hello, world."</code>.
<p>The command parameter is read only once during fire().
If you want to spawn another different command,
use life cycle management actors such RunCompositeActor.
directory
The directory in which to execute the command.
<p> This parameter is an Expert mode parameter, so it is
usually hidden. To edit it, right click on the actor, select
'Configure', then hit the 'Preferences' button and select
'Expert Mode'.
<p>This parameter is read each time the subprocess is started
in fire(). Once the subprocess is running, this parameter is not
read again until fire() is called again.
<p>The initial default value of this parameter $CWD, which
corresponds with the value of the Java virtual machine
user.dir property which is the user's current working
directory. Note that if we are running inside a menu launched
application, then ptolemy.actor.gui.jnlp.MenuApplication will
change user.dir to be the value of user.home, which is the
name of the user's home directory.
environment
The environment in which to execute the command.
<p> This parameter is an Expert mode parameter, so it is
usually hidden. To edit it, right click on the actor, select
'Configure', then hit the 'Preferences' button and select
'Expert Mode'.
<p>This parameter is read each time the subprocess is started
in fire(). Once the subprocess is running, this parameter is not
read again until fire() is called again.
<p>This parameter is an array of records that name an environment
variable and the value for the value. The format is:
<pre>
{{name = "<i>NAME1</i>", value = "</i>value1</i>"}...}
</pre>
Where <code><i>NAME1</i></code> is the name of the environment
variable, and <code><i>value1</i></code> is the value.
<p>For example <code>{{name = "PTII", value = "c:/ptII"}}</code>
would set the value of the <code>PTII</code> to <code>c:/ptII</code>.
<p>If the initial value of the parameter is <code>{{name="",
value = ""}}</code>, then the environment from the calling or parent
process is used in the new command.
<p>Note that if this parameter sets any environment variable,
then under Windows the other environment variables in the calling
or parent process might not be passed to the subprocess. This
behaviour could be platform or JVM dependent. When in doubt,
try setting the <i>command</i> value to "env" to print out the
environment.