https://ant.apache.org/: master POM (The Apache Software Foundation) 
/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package org.apache.tools.ant.taskdefs;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.io.StringReader;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Vector;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.Task;
import org.apache.tools.ant.taskdefs.condition.Os;
import org.apache.tools.ant.taskdefs.launcher.CommandLauncher;
import org.apache.tools.ant.types.Commandline;
import org.apache.tools.ant.util.FileUtils;


Runs an external program.

Since:Ant 1.2
/**
 * Runs an external program.
 *
 * @since Ant 1.2
 */
public class Execute {

    private static final int ONE_SECOND = 1000;

    
Invalid exit code. set to Integer.MAX_VALUE 
/**
     * Invalid exit code. set to {@link Integer#MAX_VALUE}
     */
    public static final int INVALID = Integer.MAX_VALUE;

    private static String antWorkingDirectory = System.getProperty("user.dir");
    private static Map<String, String> procEnvironment = null;

    
Used to destroy processes when the VM exits. 
/** Used to destroy processes when the VM exits. */
    private static ProcessDestroyer processDestroyer = new ProcessDestroyer();

    
Used for replacing env variables 
/** Used for replacing env variables */
    private static boolean environmentCaseInSensitive = false;

    static {
        if (Os.isFamily("windows")) {
            environmentCaseInSensitive = true;
        }
    }

    private String[] cmdl = null;
    private String[] env = null;
    private int exitValue = INVALID;
    private ExecuteStreamHandler streamHandler;
    private final ExecuteWatchdog watchdog;
    private File workingDirectory = null;
    private Project project = null;
    private boolean newEnvironment = false;

    
Controls whether the VM is used to launch commands, where possible. 
/** Controls whether the VM is used to launch commands, where possible. */
    private boolean useVMLauncher = true;

    
Set whether or not you want the process to be spawned.
Default is not spawned.

Params:
  • spawn – if true you do not want Ant
             to wait for the end of the process.
             Has no influence in here, the calling task contains
             and acts accordingly
Since:Ant 1.6
Deprecated:
/**
     * Set whether or not you want the process to be spawned.
     * Default is not spawned.
     *
     * @param spawn if true you do not want Ant
     *              to wait for the end of the process.
     *              Has no influence in here, the calling task contains
     *              and acts accordingly
     *
     * @since Ant 1.6
     * @deprecated
     */
    @Deprecated
    public void setSpawn(boolean spawn) {
        // Method did not do anything to begin with
    }

    
Find the list of environment variables for this process.

Returns:a map containing the environment variables.
Since:Ant 1.8.2
/**
     * Find the list of environment variables for this process.
     *
     * @return a map containing the environment variables.
     * @since Ant 1.8.2
     */
    public static synchronized Map<String, String> getEnvironmentVariables() {
        if (procEnvironment != null) {
            return procEnvironment;
        }
        if (!Os.isFamily("openvms")) {
            try {
                procEnvironment = System.getenv();
                return procEnvironment;
            } catch (Exception x) {
                x.printStackTrace(); //NOSONAR
            }
        }

        procEnvironment = new LinkedHashMap<>();
        try {
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            Execute exe = new Execute(new PumpStreamHandler(out));
            exe.setCommandline(getProcEnvCommand());
            // Make sure we do not recurse forever
            exe.setNewenvironment(true);
            int retval = exe.execute();
            if (retval != 0) {
                // Just try to use what we got
            }
            BufferedReader in =
                new BufferedReader(new StringReader(toString(out)));

            if (Os.isFamily("openvms")) {
                procEnvironment = getVMSLogicals(in);
                return procEnvironment;
            }
            StringBuilder var = null;
            String line;
            while ((line = in.readLine()) != null) {
                if (line.contains("=")) {
                    // New env var...append the previous one if we have it.
                    if (var != null) {
                        int eq = var.toString().indexOf('=');
                        procEnvironment.put(var.substring(0, eq),
                                            var.substring(eq + 1));
                    }
                    var = new StringBuilder(line);
                } else {
                    // Chunk part of previous env var (UNIX env vars can
                    // contain embedded new lines).
                    if (var == null) {
                        var = new StringBuilder(System.lineSeparator() + line);
                    } else {
                        var.append(System.lineSeparator()).append(line);
                    }
                }
            }
            // Since we "look ahead" before adding, there's one last env var.
            if (var != null) {
                int eq = var.toString().indexOf('=');
                procEnvironment.put(var.substring(0, eq), var.substring(eq + 1));
            }
        } catch (IOException exc) {
            exc.printStackTrace(); //NOSONAR
            // Just try to see how much we got
        }
        return procEnvironment;
    }

    
Find the list of environment variables for this process.

Returns:a vector containing the environment variables.
The vector elements are strings formatted like variable = value.
Deprecated:use #getEnvironmentVariables instead
/**
     * Find the list of environment variables for this process.
     *
     * @return a vector containing the environment variables.
     * The vector elements are strings formatted like variable = value.
     * @deprecated use #getEnvironmentVariables instead
     */
    @Deprecated
    public static synchronized Vector<String> getProcEnvironment() {
        Vector<String> v = new Vector<>();
        getEnvironmentVariables().forEach((key, value) -> v.add(key + "=" + value));
        return v;
    }

    
This is the operation to get our environment.
It is a notorious troublespot pre-Java1.5, and should be approached
with extreme caution.

Returns:command and arguments to get our environment
/**
     * This is the operation to get our environment.
     * It is a notorious troublespot pre-Java1.5, and should be approached
     * with extreme caution.
     *
     * @return command and arguments to get our environment
     */
    private static String[] getProcEnvCommand() {
        if (Os.isFamily("os/2")) {
            // OS/2 - use same mechanism as Windows 2000
            return new String[] {"cmd", "/c", "set"};
        }
        if (Os.isFamily("windows")) {
            // Determine if we're running under XP/2000/NT or 98/95
            if (Os.isFamily("win9x")) {
                // Windows 98/95
                return new String[] {"command.com", "/c", "set"};
            }
            // Windows XP/2000/NT/2003
            return new String[] {"cmd", "/c", "set"};
        }
        if (Os.isFamily("z/os") || Os.isFamily("unix")) {
            // On most systems one could use: /bin/sh -c env

            // Some systems have /bin/env, others /usr/bin/env, just try
            String[] cmd = new String[1];
            if (new File("/bin/env").canRead()) {
                cmd[0] = "/bin/env";
            } else if (new File("/usr/bin/env").canRead()) {
                cmd[0] = "/usr/bin/env";
            } else {
                // rely on PATH
                cmd[0] = "env";
            }
            return cmd;
        }
        if (Os.isFamily("netware") || Os.isFamily("os/400")) {
            // rely on PATH
            return new String[] {"env"};
        }
        if (Os.isFamily("openvms")) {
            return new String[] {"show", "logical"};
        }
        // MAC OS 9 and previous
        // TODO: I have no idea how to get it, someone must fix it
        return null;
    }

    
ByteArrayOutputStream#toString doesn't seem to work reliably on
OS/390, at least not the way we use it in the execution
context.

Params:
  • bos – the output stream that one wants to read.
Returns:the output stream as a string, read with
special encodings in the case of z/os and os/400.
Since:Ant 1.5
/**
     * ByteArrayOutputStream#toString doesn't seem to work reliably on
     * OS/390, at least not the way we use it in the execution
     * context.
     *
     * @param bos the output stream that one wants to read.
     * @return the output stream as a string, read with
     * special encodings in the case of z/os and os/400.
     * @since Ant 1.5
     */
    public static String toString(ByteArrayOutputStream bos) {
        if (Os.isFamily("z/os")) {
            try {
                return bos.toString("Cp1047");
            } catch (UnsupportedEncodingException e) {
                // noop default encoding used
            }
        } else if (Os.isFamily("os/400")) {
            try {
                return bos.toString("Cp500");
            } catch (UnsupportedEncodingException e) {
                // noop default encoding used
            }
        }
        return bos.toString();
    }

    
Creates a new execute object using PumpStreamHandler for
stream handling.

/**
     * Creates a new execute object using <code>PumpStreamHandler</code> for
     * stream handling.
     */
    public Execute() {
        this(new PumpStreamHandler(), null);
    }

    
Creates a new execute object.

Params:
  • streamHandler – the stream handler used to handle the input and
       output streams of the subprocess.
/**
     * Creates a new execute object.
     *
     * @param streamHandler the stream handler used to handle the input and
     *        output streams of the subprocess.
     */
    public Execute(ExecuteStreamHandler streamHandler) {
        this(streamHandler, null);
    }

    
Creates a new execute object.

Params:
  • streamHandler – the stream handler used to handle the input and
       output streams of the subprocess.
  • watchdog – a watchdog for the subprocess or null
       to disable a timeout for the subprocess.
/**
     * Creates a new execute object.
     *
     * @param streamHandler the stream handler used to handle the input and
     *        output streams of the subprocess.
     * @param watchdog a watchdog for the subprocess or <code>null</code>
     *        to disable a timeout for the subprocess.
     */
    public Execute(ExecuteStreamHandler streamHandler,
                   ExecuteWatchdog watchdog) {
        setStreamHandler(streamHandler);
        this.watchdog = watchdog;
        // By default, use the shell launcher for VMS
        //
        if (Os.isFamily("openvms")) {
            useVMLauncher = false;
        }
    }

    
Set the stream handler to use.

Params:
  • streamHandler – ExecuteStreamHandler.
Since:Ant 1.6
/**
     * Set the stream handler to use.
     *
     * @param streamHandler ExecuteStreamHandler.
     * @since Ant 1.6
     */
    public void setStreamHandler(ExecuteStreamHandler streamHandler) {
        this.streamHandler = streamHandler;
    }

    
Returns the commandline used to create a subprocess.

Returns:the commandline used to create a subprocess.
/**
     * Returns the commandline used to create a subprocess.
     *
     * @return the commandline used to create a subprocess.
     */
    public String[] getCommandline() {
        return cmdl;
    }

    
Sets the commandline of the subprocess to launch.

Params:
  • commandline – the commandline of the subprocess to launch.
/**
     * Sets the commandline of the subprocess to launch.
     *
     * @param commandline the commandline of the subprocess to launch.
     */
    public void setCommandline(String[] commandline) {
        cmdl = commandline;
    }

    
Set whether to propagate the default environment or not.

Params:
  • newenv – whether to propagate the process environment.
/**
     * Set whether to propagate the default environment or not.
     *
     * @param newenv whether to propagate the process environment.
     */
    public void setNewenvironment(boolean newenv) {
        newEnvironment = newenv;
    }

    
Returns the environment used to create a subprocess.

Returns:the environment used to create a subprocess.
/**
     * Returns the environment used to create a subprocess.
     *
     * @return the environment used to create a subprocess.
     */
    public String[] getEnvironment() {
        return (env == null || newEnvironment)
            ? env : patchEnvironment();
    }

    
Sets the environment variables for the subprocess to launch.

Params:
  • env – array of Strings, each element of which has
an environment variable settings in format key=value.
/**
     * Sets the environment variables for the subprocess to launch.
     *
     * @param env array of Strings, each element of which has
     * an environment variable settings in format <em>key=value</em>.
     */
    public void setEnvironment(String[] env) {
        this.env = env;
    }

    
Sets the working directory of the process to execute.

This is emulated using the antRun scripts unless the OS is
Windows NT in which case a cmd.exe is spawned,
or MRJ and setting user.dir works, or JDK 1.3 and there is
official support in java.lang.Runtime.

Params:
  • wd – the working directory of the process.
/**
     * Sets the working directory of the process to execute.
     *
     * <p>This is emulated using the antRun scripts unless the OS is
     * Windows NT in which case a cmd.exe is spawned,
     * or MRJ and setting user.dir works, or JDK 1.3 and there is
     * official support in java.lang.Runtime.
     *
     * @param wd the working directory of the process.
     */
    public void setWorkingDirectory(File wd) {
        workingDirectory = wd;
    }

    
Return the working directory.

Returns:the directory as a File.
Since:Ant 1.7
/**
     * Return the working directory.
     *
     * @return the directory as a File.
     * @since Ant 1.7
     */
    public File getWorkingDirectory() {
        return workingDirectory == null ? new File(antWorkingDirectory)
                                        : workingDirectory;
    }

    
Set the name of the antRun script using the project's value.

Params:
  • project – the current project.
Throws:
  • BuildException – not clear when it is going to throw an exception, but
it is the method's signature.
/**
     * Set the name of the antRun script using the project's value.
     *
     * @param project the current project.
     * @throws BuildException not clear when it is going to throw an exception, but
     * it is the method's signature.
     */
    public void setAntRun(Project project) throws BuildException {
        this.project = project;
    }

    
Launch this execution through the VM, where possible, rather than through
the OS's shell. In some cases and operating systems using the shell will
allow the shell to perform additional processing such as associating an
executable with a script, etc.

Params:
  • useVMLauncher – true if exec should launch through the VM,
                  false if the shell should be used to launch the
                  command.
/**
     * Launch this execution through the VM, where possible, rather than through
     * the OS's shell. In some cases and operating systems using the shell will
     * allow the shell to perform additional processing such as associating an
     * executable with a script, etc.
     *
     * @param useVMLauncher true if exec should launch through the VM,
     *                   false if the shell should be used to launch the
     *                   command.
     */
    public void setVMLauncher(boolean useVMLauncher) {
        this.useVMLauncher = useVMLauncher;
    }

    
Creates a process that runs a command.

Params:
  • project – the Project, only used for logging purposes, may be null.
  • command – the command to run.
  • env – the environment for the command.
  • dir – the working directory for the command.
  • useVM – use the built-in exec command for JDK 1.3 if available.
Throws:
  • IOException – forwarded from the particular launcher used.
Returns:the process started.
Since:Ant 1.5
/**
     * Creates a process that runs a command.
     *
     * @param project the Project, only used for logging purposes, may be null.
     * @param command the command to run.
     * @param env the environment for the command.
     * @param dir the working directory for the command.
     * @param useVM use the built-in exec command for JDK 1.3 if available.
     * @return the process started.
     * @throws IOException forwarded from the particular launcher used.
     * @since Ant 1.5
     */
    public static Process launch(Project project, String[] command,
                                 String[] env, File dir, boolean useVM)
        throws IOException {
        if (dir != null && !dir.exists()) {
            throw new BuildException("%s doesn't exist.", dir);
        }

        CommandLauncher vmLauncher = CommandLauncher.getVMLauncher(project);
        CommandLauncher launcher = (useVM && vmLauncher != null)
            ? vmLauncher : CommandLauncher.getShellLauncher(project);
        return launcher.exec(project, command, env, dir);
    }

    
Runs a process defined by the command line and returns its exit status.

Throws:
  • IOException – The exception is thrown, if launching
           of the subprocess failed.
Returns:the exit status of the subprocess or INVALID.
/**
     * Runs a process defined by the command line and returns its exit status.
     *
     * @return the exit status of the subprocess or <code>INVALID</code>.
     * @exception IOException The exception is thrown, if launching
     *            of the subprocess failed.
     */
    public int execute() throws IOException {
        if (workingDirectory != null && !workingDirectory.exists()) {
            throw new BuildException("%s doesn't exist.", workingDirectory);
        }
        final Process process = launch(project, getCommandline(),
                                       getEnvironment(), workingDirectory,
                                       useVMLauncher);
        try {
            streamHandler.setProcessInputStream(process.getOutputStream());
            streamHandler.setProcessOutputStream(process.getInputStream());
            streamHandler.setProcessErrorStream(process.getErrorStream());
        } catch (IOException e) {
            process.destroy();
            throw e;
        }
        streamHandler.start();

        try {
            // add the process to the list of those to destroy if the VM exits
            //
            processDestroyer.add(process);

            if (watchdog != null) {
                watchdog.start(process);
            }
            waitFor(process);

            if (watchdog != null) {
                watchdog.stop();
            }
            streamHandler.stop();
            closeStreams(process);

            if (watchdog != null) {
                watchdog.checkException();
            }
            return getExitValue();
        } catch (ThreadDeath t) {
            // #31928: forcibly kill it before continuing.
            process.destroy();
            throw t;
        } finally {
            // remove the process to the list of those to destroy if
            // the VM exits
            //
            processDestroyer.remove(process);
        }
    }

    
Starts a process defined by the command line.
Ant will not wait for this process, nor log its output.

Throws:
  • IOException – The exception is thrown, if launching
           of the subprocess failed.
Since:Ant 1.6
/**
     * Starts a process defined by the command line.
     * Ant will not wait for this process, nor log its output.
     *
     * @throws IOException The exception is thrown, if launching
     *            of the subprocess failed.
     * @since Ant 1.6
     */
    public void spawn() throws IOException {
        if (workingDirectory != null && !workingDirectory.exists()) {
            throw new BuildException("%s doesn't exist.", workingDirectory);
        }
        final Process process = launch(project, getCommandline(),
                                       getEnvironment(), workingDirectory,
                                       useVMLauncher);
        if (Os.isFamily("windows")) {
            try {
                Thread.sleep(ONE_SECOND);
            } catch (InterruptedException e) {
                project.log("interruption in the sleep after having spawned a"
                            + " process", Project.MSG_VERBOSE);
            }
        }
        OutputStream dummyOut = new OutputStream() {
            @Override
            public void write(int b) throws IOException {
                // Method intended to swallow whatever comes at it
            }
        };

        ExecuteStreamHandler handler = new PumpStreamHandler(dummyOut);
        handler.setProcessErrorStream(process.getErrorStream());
        handler.setProcessOutputStream(process.getInputStream());
        handler.start();
        process.getOutputStream().close();

        project.log("spawned process " + process.toString(),
                    Project.MSG_VERBOSE);
    }

    
Wait for a given process.

Params:
  • process – the process one wants to wait for.
/**
     * Wait for a given process.
     *
     * @param process the process one wants to wait for.
     */
    protected void waitFor(Process process) {
        try {
            process.waitFor();
            setExitValue(process.exitValue());
        } catch (InterruptedException e) {
            process.destroy();
        }
    }

    
Set the exit value.

Params:
  • value – exit value of the process.
/**
     * Set the exit value.
     *
     * @param value exit value of the process.
     */
    protected void setExitValue(int value) {
        exitValue = value;
    }

    
Query the exit value of the process.

Returns:the exit value or Execute.INVALID if no exit value has
been received.
/**
     * Query the exit value of the process.
     *
     * @return the exit value or Execute.INVALID if no exit value has
     * been received.
     */
    public int getExitValue() {
        return exitValue;
    }

    
Checks whether exitValue signals a failure on the current
system (OS specific).

Note that this method relies on the conventions of
the OS, it will return false results if the application you are
running doesn't follow these conventions. One notable
exception is the Java VM provided by HP for OpenVMS - it will
return 0 if successful (like on any other platform), but this
signals a failure on OpenVMS. So if you execute a new Java VM
on OpenVMS, you cannot trust this method.


Params:
  • exitValue – the exit value (return code) to be checked.
Returns:true if exitValue signals a failure.
/**
     * Checks whether <code>exitValue</code> signals a failure on the current
     * system (OS specific).
     *
     * <p><b>Note</b> that this method relies on the conventions of
     * the OS, it will return false results if the application you are
     * running doesn't follow these conventions. One notable
     * exception is the Java VM provided by HP for OpenVMS - it will
     * return 0 if successful (like on any other platform), but this
     * signals a failure on OpenVMS. So if you execute a new Java VM
     * on OpenVMS, you cannot trust this method.</p>
     *
     * @param exitValue the exit value (return code) to be checked.
     * @return <code>true</code> if <code>exitValue</code> signals a failure.
     */
    public static boolean isFailure(int exitValue) {
        // on openvms even exit value signals failure;
        // for other platforms nonzero exit value signals failure
        return Os.isFamily("openvms")
            ? (exitValue % 2 == 0) : (exitValue != 0);
    }

    
Did this execute return in a failure.

See Also:
  • isFailure(int)
Returns:true if and only if the exit code is interpreted as a failure
Since:Ant1.7
/**
     * Did this execute return in a failure.
     *
     * @see #isFailure(int)
     * @return true if and only if the exit code is interpreted as a failure
     * @since Ant1.7
     */
    public boolean isFailure() {
        return isFailure(getExitValue());
    }

    
Test for an untimely death of the process.

Returns:true if a watchdog had to kill the process.
Since:Ant 1.5
/**
     * Test for an untimely death of the process.
     *
     * @return true if a watchdog had to kill the process.
     * @since Ant 1.5
     */
    public boolean killedProcess() {
        return watchdog != null && watchdog.killedProcess();
    }

    
Patch the current environment with the new values from the user.

Returns:the patched environment.
/**
     * Patch the current environment with the new values from the user.
     *
     * @return the patched environment.
     */
    private String[] patchEnvironment() {
        // On OpenVMS Runtime#exec() doesn't support the environment array,
        // so we only return the new values which then will be set in
        // the generated DCL script, inheriting the parent process environment
        if (Os.isFamily("openvms")) {
            return env;
        }
        Map<String, String> osEnv =
            new LinkedHashMap<>(getEnvironmentVariables());
        for (String keyValue : env) {
            String key = keyValue.substring(0, keyValue.indexOf('='));
            // Find the key in the current environment copy
            // and remove it.

            // Try without changing case first
            if (osEnv.remove(key) == null && environmentCaseInSensitive) {
                // not found, maybe perform a case insensitive search

                for (String osEnvItem : osEnv.keySet()) {
                    // Nb: using default locale as key is a env name
                    if (osEnvItem.equalsIgnoreCase(key)) {
                        // Use the original case of the key
                        key = osEnvItem;
                        break;
                    }
                }
            }

            // Add the key to the environment copy
            osEnv.put(key, keyValue.substring(key.length() + 1));
        }

        return osEnv.entrySet().stream()
            .map(e -> e.getKey() + "=" + e.getValue()).toArray(String[]::new);
    }

    
A utility method that runs an external command. Writes the output and
error streams of the command to the project log.

Params:
  • task – The task that the command is part of. Used for logging
  • cmdline – The command to execute.
Throws:
/**
     * A utility method that runs an external command. Writes the output and
     * error streams of the command to the project log.
     *
     * @param task The task that the command is part of. Used for logging
     * @param cmdline The command to execute.
     * @throws BuildException if the command does not exit successfully.
     */
    public static void runCommand(Task task, String... cmdline)
        throws BuildException {
        try {
            task.log(Commandline.describeCommand(cmdline),
                     Project.MSG_VERBOSE);
            Execute exe = new Execute(
                new LogStreamHandler(task, Project.MSG_INFO, Project.MSG_ERR));
            exe.setAntRun(task.getProject());
            exe.setCommandline(cmdline);
            int retval = exe.execute();
            if (isFailure(retval)) {
                throw new BuildException(cmdline[0]
                    + " failed with return code " + retval, task.getLocation());
            }
        } catch (IOException exc) {
            throw new BuildException("Could not launch " + cmdline[0] + ": "
                + exc, task.getLocation());
        }
    }

    
Close the streams belonging to the given Process.

Params:
  • process – the Process.
/**
     * Close the streams belonging to the given Process.
     *
     * @param process the <code>Process</code>.
     */
    public static void closeStreams(Process process) {
        FileUtils.close(process.getInputStream());
        FileUtils.close(process.getOutputStream());
        FileUtils.close(process.getErrorStream());
    }

    
This method is VMS specific and used by getEnvironmentVariables().
Parses VMS logicals from in and returns them as a Map.
in is expected to be the
output of "SHOW LOGICAL". The method takes care of parsing the output
correctly as well as making sure that a logical defined in multiple
tables only gets added from the highest order table. Logicals with
multiple equivalence names are mapped to a variable with multiple
values separated by a comma (,).

/**
     * This method is VMS specific and used by getEnvironmentVariables().
     *
     * Parses VMS logicals from <code>in</code> and returns them as a Map.
     * <code>in</code> is expected to be the
     * output of "SHOW LOGICAL". The method takes care of parsing the output
     * correctly as well as making sure that a logical defined in multiple
     * tables only gets added from the highest order table. Logicals with
     * multiple equivalence names are mapped to a variable with multiple
     * values separated by a comma (,).
     */
    private static Map<String, String> getVMSLogicals(BufferedReader in)
        throws IOException {
        Map<String, String> logicals = new HashMap<>();
        String logName = null, logValue = null, newLogName;
        String line;
        // CheckStyle:MagicNumber OFF
        while ((line = in.readLine()) != null) {
            // parse the VMS logicals into required format ("VAR=VAL[,VAL2]")
            if (line.startsWith("\t=")) {
                // further equivalence name of previous logical
                if (logName != null) {
                    logValue += "," + line.substring(4, line.length() - 1);
                }
            } else if (line.startsWith("  \"")) {
                // new logical?
                if (logName != null) {
                    logicals.put(logName, logValue);
                }
                int eqIndex = line.indexOf('=');
                newLogName = line.substring(3, eqIndex - 2);
                if (logicals.containsKey(newLogName)) {
                    // already got this logical from a higher order table
                    logName = null;
                } else {
                    logName = newLogName;
                    logValue = line.substring(eqIndex + 3, line.length() - 1);
                }
            }
        }
        // CheckStyle:MagicNumber ON
        // Since we "look ahead" before adding, there's one last env var.
        if (logName != null) {
            logicals.put(logName, logValue);
        }
        return logicals;
    }
}