java/6 : java/lang/ProcessBuilder.java

ProcessBuilder
https://openjdk.java.net/
GPLv2 + Classpath Exception
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 * accompanied this code).
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package java.lang;

import java.io.File;
import java.io.IOException;
import java.security.AccessControlException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

This class is used to create operating system processes.
Each ProcessBuilder instance manages a collection of process attributes. The start() method creates a new Process instance with those attributes. The start() method can be invoked repeatedly from the same instance to create new subprocesses with identical or related attributes. 
Each process builder manages these process attributes:

a command, a list of strings which signifies the
external program file to be invoked and its arguments, if any.
Which string lists represent a valid operating system command is
system-dependent.  For example, it is common for each conceptual
argument to be an element in this list, but there are operating
systems where programs are expected to tokenize command line
strings themselves - on such a system a Java implementation might
require commands to contain exactly two elements.
an environment, which is a system-dependent mapping from
variables to values. The initial value is a copy of the environment of the current process (see System.getenv()). 
a working directory.  The default value is the current
working directory of the current process, usually the directory
named by the system property user.dir.
a redirectErrorStream property.  Initially, this property
is false, meaning that the standard output and error output of a subprocess are sent to two separate streams, which can be accessed using the Process.getInputStream() and Process.getErrorStream() methods. If the value is set to true, the standard error is merged with the standard output. This makes it easier to correlate error messages with the corresponding output. In this case, the merged data can be read from the stream returned by Process.getInputStream(), while reading from the stream returned by Process.getErrorStream() will get an immediate end of file. 
Modifying a process builder's attributes will affect processes subsequently started by that object's start() method, but will never affect previously started processes or the Java process itself. 
Most error checking is performed by the start() method. It is possible to modify the state of an object so that start() will fail. For example, setting the command attribute to an empty list will not throw an exception unless start() is invoked. 
Note that this class is not synchronized.
If multiple threads access a ProcessBuilder instance
concurrently, and at least one of the threads modifies one of the
attributes structurally, it must be synchronized externally.
Starting a new process which uses the default working directory
and environment is easy:
Process p = new ProcessBuilder("myCommand", "myArg").start();

Here is an example that starts a process with a modified working
directory and environment:
ProcessBuilder pb = new ProcessBuilder("myCommand", "myArg1", "myArg2");
Map<String, String> env = pb.environment();
env.put("VAR1", "myValue");
env.remove("OTHERVAR");
env.put("VAR2", env.get("VAR1") + "suffix");
pb.directory(new File("myDir"));
Process p = pb.start();

To start a process with an explicit set of environment variables, first call Map.clear() before adding environment variables. 
Since: 1.5/**
 * This class is used to create operating system processes.
 *
 * <p>Each <code>ProcessBuilder</code> instance manages a collection
 * of process attributes.  The {@link #start()} method creates a new
 * {@link Process} instance with those attributes.  The {@link
 * #start()} method can be invoked repeatedly from the same instance
 * to create new subprocesses with identical or related attributes.
 *
 * <p>Each process builder manages these process attributes:
 *
 * <ul>
 *
 * <li>a <i>command</i>, a list of strings which signifies the
 * external program file to be invoked and its arguments, if any.
 * Which string lists represent a valid operating system command is
 * system-dependent.  For example, it is common for each conceptual
 * argument to be an element in this list, but there are operating
 * systems where programs are expected to tokenize command line
 * strings themselves - on such a system a Java implementation might
 * require commands to contain exactly two elements.
 *
 * <li>an <i>environment</i>, which is a system-dependent mapping from
 * <i>variables</i> to <i>values</i>.  The initial value is a copy of
 * the environment of the current process (see {@link System#getenv()}).
 *
 * <li>a <i>working directory</i>.  The default value is the current
 * working directory of the current process, usually the directory
 * named by the system property <code>user.dir</code>.
 *
 * <li>a <i>redirectErrorStream</i> property.  Initially, this property
 * is <code>false</code>, meaning that the standard output and error
 * output of a subprocess are sent to two separate streams, which can
 * be accessed using the {@link Process#getInputStream()} and {@link
 * Process#getErrorStream()} methods.  If the value is set to
 * <code>true</code>, the standard error is merged with the standard
 * output.  This makes it easier to correlate error messages with the
 * corresponding output.  In this case, the merged data can be read
 * from the stream returned by {@link Process#getInputStream()}, while
 * reading from the stream returned by {@link
 * Process#getErrorStream()} will get an immediate end of file.
 *
 * </ul>
 *
 * <p>Modifying a process builder's attributes will affect processes
 * subsequently started by that object's {@link #start()} method, but
 * will never affect previously started processes or the Java process
 * itself.
 *
 * <p>Most error checking is performed by the {@link #start()} method.
 * It is possible to modify the state of an object so that {@link
 * #start()} will fail.  For example, setting the command attribute to
 * an empty list will not throw an exception unless {@link #start()}
 * is invoked.
 *
 * <p><strong>Note that this class is not synchronized.</strong>
 * If multiple threads access a <code>ProcessBuilder</code> instance
 * concurrently, and at least one of the threads modifies one of the
 * attributes structurally, it <i>must</i> be synchronized externally.
 *
 * <p>Starting a new process which uses the default working directory
 * and environment is easy:
 *
 * <blockquote><pre>
 * Process p = new ProcessBuilder("myCommand", "myArg").start();
 * </pre></blockquote>
 *
 * <p>Here is an example that starts a process with a modified working
 * directory and environment:
 *
 * <blockquote><pre>
 * ProcessBuilder pb = new ProcessBuilder("myCommand", "myArg1", "myArg2");
 * Map&lt;String, String&gt; env = pb.environment();
 * env.put("VAR1", "myValue");
 * env.remove("OTHERVAR");
 * env.put("VAR2", env.get("VAR1") + "suffix");
 * pb.directory(new File("myDir"));
 * Process p = pb.start();
 * </pre></blockquote>
 *
 * <p>To start a process with an explicit set of environment
 * variables, first call {@link java.util.Map#clear() Map.clear()}
 * before adding environment variables.
 *
 * @since 1.5
 */

public final class ProcessBuilder
{
    private List<String> command;
    private File directory;
    private Map<String,String> environment;
    private boolean redirectErrorStream;

    Constructs a process builder with the specified operating
system program and arguments.  This constructor does not
make a copy of the command list.  Subsequent
updates to the list will be reflected in the state of the
process builder.  It is not checked whether
command corresponds to a valid operating system
command.
Params: command –  The list containing the program and its arguments
Throws: NullPointerException – 
         If the argument is null/**
     * Constructs a process builder with the specified operating
     * system program and arguments.  This constructor does <i>not</i>
     * make a copy of the <code>command</code> list.  Subsequent
     * updates to the list will be reflected in the state of the
     * process builder.  It is not checked whether
     * <code>command</code> corresponds to a valid operating system
     * command.</p>
     *
     * @param   command  The list containing the program and its arguments
     *
     * @throws  NullPointerException
     *          If the argument is <code>null</code>
     */
    public ProcessBuilder(List<String> command) {
        if (command == null)
            throw new NullPointerException();
        this.command = command;
    }

    Constructs a process builder with the specified operating
system program and arguments.  This is a convenience
constructor that sets the process builder's command to a string
list containing the same strings as the command
array, in the same order.  It is not checked whether
command corresponds to a valid operating system
command.
Params: command –  A string array containing the program and its arguments/**
     * Constructs a process builder with the specified operating
     * system program and arguments.  This is a convenience
     * constructor that sets the process builder's command to a string
     * list containing the same strings as the <code>command</code>
     * array, in the same order.  It is not checked whether
     * <code>command</code> corresponds to a valid operating system
     * command.</p>
     *
     * @param   command  A string array containing the program and its arguments
     */
    public ProcessBuilder(String... command) {
        this.command = new ArrayList<String>(command.length);
        for (String arg : command)
            this.command.add(arg);
    }

    Sets this process builder's operating system program and
arguments.  This method does not make a copy of the
command list.  Subsequent updates to the list will
be reflected in the state of the process builder.  It is not
checked whether command corresponds to a valid
operating system command.
Params: command –  The list containing the program and its arguments
Throws: NullPointerException – 
         If the argument is null
Returns:  This process builder/**
     * Sets this process builder's operating system program and
     * arguments.  This method does <i>not</i> make a copy of the
     * <code>command</code> list.  Subsequent updates to the list will
     * be reflected in the state of the process builder.  It is not
     * checked whether <code>command</code> corresponds to a valid
     * operating system command.</p>
     *
     * @param   command  The list containing the program and its arguments
     * @return  This process builder
     *
     * @throws  NullPointerException
     *          If the argument is <code>null</code>
     */
    public ProcessBuilder command(List<String> command) {
        if (command == null)
            throw new NullPointerException();
        this.command = command;
        return this;
    }

    Sets this process builder's operating system program and
arguments.  This is a convenience method that sets the command
to a string list containing the same strings as the
command array, in the same order.  It is not
checked whether command corresponds to a valid
operating system command.
Params: command –  A string array containing the program and its arguments
Returns:  This process builder/**
     * Sets this process builder's operating system program and
     * arguments.  This is a convenience method that sets the command
     * to a string list containing the same strings as the
     * <code>command</code> array, in the same order.  It is not
     * checked whether <code>command</code> corresponds to a valid
     * operating system command.</p>
     *
     * @param   command  A string array containing the program and its arguments
     * @return  This process builder
     */
    public ProcessBuilder command(String... command) {
        this.command = new ArrayList<String>(command.length);
        for (String arg : command)
            this.command.add(arg);
        return this;
    }

    Returns this process builder's operating system program and
arguments.  The returned list is not a copy.  Subsequent
updates to the list will be reflected in the state of this
process builder.
Returns:  This process builder's program and its arguments/**
     * Returns this process builder's operating system program and
     * arguments.  The returned list is <i>not</i> a copy.  Subsequent
     * updates to the list will be reflected in the state of this
     * process builder.</p>
     *
     * @return  This process builder's program and its arguments
     */
    public List<String> command() {
        return command;
    }

    Returns a string map view of this process builder's environment. Whenever a process builder is created, the environment is initialized to a copy of the current process environment (see System.getenv()). Subprocesses subsequently started by this object's start() method will use this map as their environment. The returned object may be modified using ordinary Map operations. These modifications will be visible to subprocesses started via the start() method. Two ProcessBuilder instances always
contain independent process environments, so changes to the
returned map will never be reflected in any other
ProcessBuilder instance or the values returned by System.getenv. 
If the system does not support environment variables, an
empty map is returned.
The returned map does not permit null keys or values. Attempting to insert or query the presence of a null key or value will throw a NullPointerException. Attempting to query the presence of a key or value which is not of type String will throw a ClassCastException. 
The behavior of the returned map is system-dependent. A system may not allow modifications to environment variables or may forbid certain variable names or values. For this reason, attempts to modify the map may fail with UnsupportedOperationException or IllegalArgumentException if the modification is not permitted by the operating system. 
Since the external format of environment variable names and
values is system-dependent, there may not be a one-to-one
mapping between them and Java's Unicode strings.  Nevertheless,
the map is implemented in such a way that environment variables
which are not modified by Java code will have an unmodified
native representation in the subprocess.
The returned map and its collection views may not obey the general contract of the Object.equals and Object.hashCode methods. 
The returned map is typically case-sensitive on all platforms.
If a security manager exists, its checkPermission method is called with a RuntimePermission("getenv.*") permission. This may result in a SecurityException being thrown. 
When passing information to a Java subprocess,
system properties
are generally preferred over environment variables.
Throws: SecurityException –  If a security manager exists and its checkPermission method doesn't allow access to the process environment
See Also: Runtime.exec(String[], String[], File)
System.getenv()
Returns:  This process builder's environment/**
     * Returns a string map view of this process builder's environment.
     *
     * Whenever a process builder is created, the environment is
     * initialized to a copy of the current process environment (see
     * {@link System#getenv()}).  Subprocesses subsequently started by
     * this object's {@link #start()} method will use this map as
     * their environment.
     *
     * <p>The returned object may be modified using ordinary {@link
     * java.util.Map Map} operations.  These modifications will be
     * visible to subprocesses started via the {@link #start()}
     * method.  Two <code>ProcessBuilder</code> instances always
     * contain independent process environments, so changes to the
     * returned map will never be reflected in any other
     * <code>ProcessBuilder</code> instance or the values returned by
     * {@link System#getenv System.getenv}.
     *
     * <p>If the system does not support environment variables, an
     * empty map is returned.
     *
     * <p>The returned map does not permit null keys or values.
     * Attempting to insert or query the presence of a null key or
     * value will throw a {@link NullPointerException}.
     * Attempting to query the presence of a key or value which is not
     * of type {@link String} will throw a {@link ClassCastException}.
     *
     * <p>The behavior of the returned map is system-dependent.  A
     * system may not allow modifications to environment variables or
     * may forbid certain variable names or values.  For this reason,
     * attempts to modify the map may fail with
     * {@link UnsupportedOperationException} or
     * {@link IllegalArgumentException}
     * if the modification is not permitted by the operating system.
     *
     * <p>Since the external format of environment variable names and
     * values is system-dependent, there may not be a one-to-one
     * mapping between them and Java's Unicode strings.  Nevertheless,
     * the map is implemented in such a way that environment variables
     * which are not modified by Java code will have an unmodified
     * native representation in the subprocess.
     *
     * <p>The returned map and its collection views may not obey the
     * general contract of the {@link Object#equals} and
     * {@link Object#hashCode} methods.
     *
     * <p>The returned map is typically case-sensitive on all platforms.
     *
     * <p>If a security manager exists, its
     * {@link SecurityManager#checkPermission checkPermission}
     * method is called with a
     * <code>{@link RuntimePermission}("getenv.*")</code>
     * permission.  This may result in a {@link SecurityException} being
     * thrown.
     *
     * <p>When passing information to a Java subprocess,
     * <a href=System.html#EnvironmentVSSystemProperties>system properties</a>
     * are generally preferred over environment variables.</p>
     *
     * @return  This process builder's environment
     *
     * @throws  SecurityException
     *          If a security manager exists and its
     *          {@link SecurityManager#checkPermission checkPermission}
     *          method doesn't allow access to the process environment
     *
     * @see     Runtime#exec(String[],String[],java.io.File)
     * @see     System#getenv()
     */
    public Map<String,String> environment() {
        SecurityManager security = System.getSecurityManager();
        if (security != null)
            security.checkPermission(new RuntimePermission("getenv.*"));

        if (environment == null)
            environment = ProcessEnvironment.environment();

        assert environment != null;

        return environment;
    }

    // Only for use by Runtime.exec(...envp...)
    ProcessBuilder environment(String[] envp) {
        assert environment == null;
        if (envp != null) {
            environment = ProcessEnvironment.emptyEnvironment(envp.length);
            assert environment != null;

            for (String envstring : envp) {
                // Before 1.5, we blindly passed invalid envstrings
                // to the child process.
                // We would like to throw an exception, but do not,
                // for compatibility with old broken code.

                // Silently discard any trailing junk.
                if (envstring.indexOf((int) '\u0000') != -1)
                    envstring = envstring.replaceFirst("\u0000.*", "");

                int eqlsign =
                    envstring.indexOf('=', ProcessEnvironment.MIN_NAME_LENGTH);
                // Silently ignore envstrings lacking the required `='.
                if (eqlsign != -1)
                    environment.put(envstring.substring(0,eqlsign),
                                    envstring.substring(eqlsign+1));
            }
        }
        return this;
    }

    Returns this process builder's working directory. Subprocesses subsequently started by this object's start() method will use this as their working directory. The returned value may be null -- this means to use
the working directory of the current Java process, usually the
directory named by the system property user.dir,
as the working directory of the child process.
Returns:  This process builder's working directory/**
     * Returns this process builder's working directory.
     *
     * Subprocesses subsequently started by this object's {@link
     * #start()} method will use this as their working directory.
     * The returned value may be <code>null</code> -- this means to use
     * the working directory of the current Java process, usually the
     * directory named by the system property <code>user.dir</code>,
     * as the working directory of the child process.</p>
     *
     * @return  This process builder's working directory
     */
    public File directory() {
        return directory;
    }

    Sets this process builder's working directory. Subprocesses subsequently started by this object's start() method will use this as their working directory. The argument may be null -- this means to use the
working directory of the current Java process, usually the
directory named by the system property user.dir,
as the working directory of the child process.
Params: directory –  The new working directory
Returns:  This process builder/**
     * Sets this process builder's working directory.
     *
     * Subprocesses subsequently started by this object's {@link
     * #start()} method will use this as their working directory.
     * The argument may be <code>null</code> -- this means to use the
     * working directory of the current Java process, usually the
     * directory named by the system property <code>user.dir</code>,
     * as the working directory of the child process.</p>
     *
     * @param   directory  The new working directory
     * @return  This process builder
     */
    public ProcessBuilder directory(File directory) {
        this.directory = directory;
        return this;
    }

    Tells whether this process builder merges standard error and
standard output.
If this property is true, then any error output generated by subprocesses subsequently started by this object's start() method will be merged with the standard output, so that both can be read using the Process.getInputStream() method. This makes it easier to correlate error messages with the corresponding output. The initial value is false.
Returns:  This process builder's redirectErrorStream property/**
     * Tells whether this process builder merges standard error and
     * standard output.
     *
     * <p>If this property is <code>true</code>, then any error output
     * generated by subprocesses subsequently started by this object's
     * {@link #start()} method will be merged with the standard
     * output, so that both can be read using the
     * {@link Process#getInputStream()} method.  This makes it easier
     * to correlate error messages with the corresponding output.
     * The initial value is <code>false</code>.</p>
     *
     * @return  This process builder's <code>redirectErrorStream</code> property
     */
    public boolean redirectErrorStream() {
        return redirectErrorStream;
    }

    Sets this process builder's redirectErrorStream property.
If this property is true, then any error output generated by subprocesses subsequently started by this object's start() method will be merged with the standard output, so that both can be read using the Process.getInputStream() method. This makes it easier to correlate error messages with the corresponding output. The initial value is false.
Params: redirectErrorStream –  The new property value
Returns:  This process builder/**
     * Sets this process builder's <code>redirectErrorStream</code> property.
     *
     * <p>If this property is <code>true</code>, then any error output
     * generated by subprocesses subsequently started by this object's
     * {@link #start()} method will be merged with the standard
     * output, so that both can be read using the
     * {@link Process#getInputStream()} method.  This makes it easier
     * to correlate error messages with the corresponding output.
     * The initial value is <code>false</code>.</p>
     *
     * @param   redirectErrorStream  The new property value
     * @return  This process builder
     */
    public ProcessBuilder redirectErrorStream(boolean redirectErrorStream) {
        this.redirectErrorStream = redirectErrorStream;
        return this;
    }

    Starts a new process using the attributes of this process builder.
The new process will invoke the command and arguments given by command(), in a working directory as given by directory(), with a process environment as given by environment(). 
This method checks that the command is a valid operating
system command.  Which commands are valid is system-dependent,
but at the very least the command must be a non-empty list of
non-null strings.
If there is a security manager, its checkExec method is called with the first component of this object's command array as its argument. This may result in a SecurityException being thrown. 
Starting an operating system process is highly system-dependent.
Among the many things that can go wrong are:

The operating system program file was not found.
Access to the program file was denied.
The working directory does not exist.

In such cases an exception will be thrown. The exact nature of the exception is system-dependent, but it will always be a subclass of IOException. 
Subsequent modifications to this process builder will not affect the returned Process.
Throws: NullPointerException – 
         If an element of the command list is null
IndexOutOfBoundsException – 
         If the command is an empty list (has size 0)
SecurityException –  If a security manager exists and its checkExec method doesn't allow creation of the subprocess
IOException – 
         If an I/O error occurs
See Also: Runtime.exec(String[], String[], File)
SecurityManager.checkExec(String)
Returns:  A new Process object for managing the subprocess/**
     * Starts a new process using the attributes of this process builder.
     *
     * <p>The new process will
     * invoke the command and arguments given by {@link #command()},
     * in a working directory as given by {@link #directory()},
     * with a process environment as given by {@link #environment()}.
     *
     * <p>This method checks that the command is a valid operating
     * system command.  Which commands are valid is system-dependent,
     * but at the very least the command must be a non-empty list of
     * non-null strings.
     *
     * <p>If there is a security manager, its
     * {@link SecurityManager#checkExec checkExec}
     * method is called with the first component of this object's
     * <code>command</code> array as its argument. This may result in
     * a {@link SecurityException} being thrown.
     *
     * <p>Starting an operating system process is highly system-dependent.
     * Among the many things that can go wrong are:
     * <ul>
     * <li>The operating system program file was not found.
     * <li>Access to the program file was denied.
     * <li>The working directory does not exist.
     * </ul>
     *
     * <p>In such cases an exception will be thrown.  The exact nature
     * of the exception is system-dependent, but it will always be a
     * subclass of {@link IOException}.
     *
     * <p>Subsequent modifications to this process builder will not
     * affect the returned {@link Process}.</p>
     *
     * @return  A new {@link Process} object for managing the subprocess
     *
     * @throws  NullPointerException
     *          If an element of the command list is null
     *
     * @throws  IndexOutOfBoundsException
     *          If the command is an empty list (has size <code>0</code>)
     *
     * @throws  SecurityException
     *          If a security manager exists and its
     *          {@link SecurityManager#checkExec checkExec}
     *          method doesn't allow creation of the subprocess
     *
     * @throws  IOException
     *          If an I/O error occurs
     *
     * @see     Runtime#exec(String[], String[], java.io.File)
     * @see     SecurityManager#checkExec(String)
     */
    public Process start() throws IOException {
        // Must convert to array first -- a malicious user-supplied
        // list might try to circumvent the security check.
        String[] cmdarray = command.toArray(new String[command.size()]);
        cmdarray = cmdarray.clone();
        for (String arg : cmdarray)
            if (arg == null)
                throw new NullPointerException();
        // Throws IndexOutOfBoundsException if command is empty
        String prog = cmdarray[0];

        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkExec(prog);
        }

        String dir = directory == null ? null : directory.toString();

        for (int i = 1; i < cmdarray.length; i++) {
            if (cmdarray[i].indexOf('\u0000') >= 0) {
                throw new IOException("invalid null character in command");
            }
        }

        try {
            return ProcessImpl.start(cmdarray,
                                     environment,
                                     dir,
                                     redirectErrorStream);
        } catch (IOException e) {
            String exceptionInfo = ": " + e.getMessage();
            Throwable cause = e;
            if (security != null) {
                // Can not disclose the fail reason for read-protected files.
                try {
                    security.checkRead(prog);
                } catch (AccessControlException ace) {
                    exceptionInfo = "";
                    cause = ace;
                }
            }
            // It's much easier for us to create a high-quality error
            // message than the low-level C code which found the problem.
            throw new IOException(
                "Cannot run program \"" + prog + "\""
                + (dir == null ? "" : " (in directory \"" + dir + "\")")
                + exceptionInfo,
                cause);
        } catch (IllegalArgumentException e) {
            String exceptionInfo = ": " + e.getMessage();
            // It's much easier for us to create a high-quality error
            // message than the low-level C code which found the problem.
            throw new IOException(
                "Cannot run program \"" + prog + "\""
                + (dir == null ? "" : " (in directory \"" + dir + "\")")
                + exceptionInfo,
                e);
        }
    }
}
Params:	command – The list containing the program and its arguments
Throws:	NullPointerException – If the argument is `null`
Params:	command – A string array containing the program and its arguments
Returns:	This process builder
Throws:	SecurityException – If a security manager exists and its `checkPermission` method doesn't allow access to the process environment
See Also:	Runtime.exec(String[], String[], File) System.getenv()
Returns:	This process builder's environment
Params:	directory – The new working directory
Returns:	This process builder
Params:	redirectErrorStream – The new property value
Returns:	This process builder
Throws:	NullPointerException – If an element of the command list is null IndexOutOfBoundsException – If the command is an empty list (has size `0`) SecurityException – If a security manager exists and its `checkExec` method doesn't allow creation of the subprocess IOException – If an I/O error occurs
See Also:	Runtime.exec(String[], String[], File) SecurityManager.checkExec(String)
Returns:	A new `Process` object for managing the subprocess
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java/ 6/ java/lang/ProcessBuilder.java
