Scott: /* booleanCommand */

2011-01-31T22:07:36Z

booleanCommand

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In Unix,
<pre>
/bin/sh -c <commands>
</pre>
is a way to ask the shell to process <commands>

In Windows, you may need
<pre>
command \c dir
</pre>
or
<pre>
cmd \c dir
</pre>
to execute DOS shell commands like <code>dir</code>. Otherwise, the command name should suffice.

==StreamGobbler==
See http://hacks.oreilly.com/pub/h/1092 for a good description of this
<source lang="java">
import java.io.*;

public class StreamGobbler extends Thread {
private InputStream is;
private StringBuffer buffer;

StreamGobbler(InputStream is, StringBuffer buffer) {
this.is = is;
this.buffer = buffer;
this.start();
}

StreamGobbler(InputStream is) {
this(is, null);
}

public void run() {
int nextChar;
if (buffer == null) {
try {
while ((nextChar = is.read()) != -1) {} // do nothing
} catch (IOException ioe) {
ioe.printStackTrace();
}
} else {
try {
while ((nextChar = is.read()) != -1) {
buffer.append((char) nextChar);
}
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
}
}
</source>

==booleanCommand==
<source lang="java">
public static boolean booleanCommand(String command) {
Runtime rt = Runtime.getRuntime();
String[] callAndArgs = {"/bin/bash", "-c", command};
int exitValue = Integer.MIN_VALUE;
Process child = null;
try {
child = rt.exec(callAndArgs);
StreamGobbler errorGobbler = new StreamGobbler(child.getErrorStream());
StreamGobbler inputGobbler = new StreamGobbler(child.getInputStream());
exitValue = child.waitFor();
} catch (IOException e) {
logger.error("IOException starting process!", e);
} catch (InterruptedException e) {
logger.error("Interrupted waiting for process!", e);
}
if (exitValue == Integer.MIN_VALUE) {
logger.error("boolean command " + command + " failed to execute!");
}
return (exitValue == 0);
}
</source>

==stringCommandIgnoreReturnValue==
<source lang="java">
public static String stringCommandIgnoreReturnValue(String command) {
Runtime rt = Runtime.getRuntime();
String[] callAndArgs = {"/bin/bash", "-c", command};
StringBuffer inputBuffer = new StringBuffer();
int exitValue = Integer.MIN_VALUE;
Process child = null;
try {
child = rt.exec(callAndArgs);
StreamGobbler errorGobbler = new StreamGobbler(child.getErrorStream());
StreamGobbler inputGobbler = new StreamGobbler(child.getInputStream(), inputBuffer);
exitValue = child.waitFor();
} catch (IOException e) {
e.printStackTrace();
System.err.println("IOException starting process!");
} catch (InterruptedException e) {
System.err.println("Interrupted waiting for process!");
}
if (exitValue == Integer.MIN_VALUE) {
throw new IllegalStateException("command " + command + " failed to return any output!");
}
return inputBuffer.toString();
}
</source>

Java System Calls - Revision history

Scott: /* booleanCommand */