public final class ProcessBuilder extends Object
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:
System.getenv()).
 user.dir.
 Process.getOutputStream().  However, standard input may
 be redirected to another source using
 redirectInput.
 In this case, Process.getOutputStream() will return a
 null output stream, for which:
 
 Process.getInputStream() and
 Process.getErrorStream().  However, standard output and
 standard error may be redirected to other destinations using
 redirectOutput and
 redirectError.
 In this case, Process.getInputStream() and/or
 Process.getErrorStream() will return a null input
 stream, for which:
 
 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, then:
 
redirectOutput
 redirectError
 method is ignored when creating a subprocess
 Process.getErrorStream() will
 always be a null input stream
 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, and redirects standard output and error to be appended to a log file:
 
 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"));
 File log = new File("log");
 pb.redirectErrorStream(true);
 pb.redirectOutput(Redirect.appendTo(log));
 Process p = pb.start();
 assert pb.redirectInput() == Redirect.PIPE;
 assert pb.redirectOutput().file() == log;
 assert p.getInputStream().read() == -1;
 
 To start a process with an explicit set of environment
 variables, first call Map.clear()
 before adding environment variables.
| Modifier and Type | Class and Description | 
|---|---|
| static class  | ProcessBuilder.RedirectRepresents a source of subprocess input or a destination of
 subprocess output. | 
| Constructor and Description | 
|---|
| ProcessBuilder(List<String> command)Constructs a process builder with the specified operating
 system program and arguments. | 
| ProcessBuilder(String... command)Constructs a process builder with the specified operating
 system program and arguments. | 
| Modifier and Type | Method and Description | 
|---|---|
| List<String> | command()Returns this process builder's operating system program and
 arguments. | 
| ProcessBuilder | command(List<String> command)Sets this process builder's operating system program and
 arguments. | 
| ProcessBuilder | command(String... command)Sets this process builder's operating system program and
 arguments. | 
| File | directory()Returns this process builder's working directory. | 
| ProcessBuilder | directory(File directory)Sets this process builder's working directory. | 
| Map<String,String> | environment()Returns a string map view of this process builder's environment. | 
| ProcessBuilder | inheritIO()Sets the source and destination for subprocess standard I/O
 to be the same as those of the current Java process. | 
| ProcessBuilder.Redirect | redirectError()Returns this process builder's standard error destination. | 
| ProcessBuilder | redirectError(File file)Sets this process builder's standard error destination to a file. | 
| ProcessBuilder | redirectError(ProcessBuilder.Redirect destination)Sets this process builder's standard error destination. | 
| boolean | redirectErrorStream()Tells whether this process builder merges standard error and
 standard output. | 
| ProcessBuilder | redirectErrorStream(boolean redirectErrorStream)Sets this process builder's  redirectErrorStreamproperty. | 
| ProcessBuilder.Redirect | redirectInput()Returns this process builder's standard input source. | 
| ProcessBuilder | redirectInput(File file)Sets this process builder's standard input source to a file. | 
| ProcessBuilder | redirectInput(ProcessBuilder.Redirect source)Sets this process builder's standard input source. | 
| ProcessBuilder.Redirect | redirectOutput()Returns this process builder's standard output destination. | 
| ProcessBuilder | redirectOutput(File file)Sets this process builder's standard output destination to a file. | 
| ProcessBuilder | redirectOutput(ProcessBuilder.Redirect destination)Sets this process builder's standard output destination. | 
| Process | start()Starts a new process using the attributes of this process builder. | 
public ProcessBuilder(List<String> command)
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.command - the list containing the program and its argumentsNullPointerException - if the argument is nullpublic ProcessBuilder(String... command)
command
 array, in the same order.  It is not checked whether
 command corresponds to a valid operating system
 command.command - a string array containing the program and its argumentspublic ProcessBuilder command(List<String> command)
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.command - the list containing the program and its argumentsNullPointerException - if the argument is nullpublic ProcessBuilder command(String... command)
command array, in the same order.  It is not
 checked whether command corresponds to a valid
 operating system command.command - a string array containing the program and its argumentspublic List<String> command()
public Map<String,String> environment()
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(java.lang.Object) 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.
SecurityException - if a security manager exists and its
         checkPermission
         method doesn't allow access to the process environmentRuntime.exec(String[],String[],java.io.File), 
System.getenv()public File directory()
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.public ProcessBuilder directory(File directory)
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.directory - the new working directorypublic ProcessBuilder redirectInput(ProcessBuilder.Redirect source)
start()
 method obtain their standard input from this source.
 If the source is Redirect.PIPE
 (the initial value), then the standard input of a
 subprocess can be written to using the output stream
 returned by Process.getOutputStream().
 If the source is set to any other value, then
 Process.getOutputStream() will return a
 null output stream.
source - the new standard input sourceIllegalArgumentException - if the redirect does not correspond to a valid source
         of data, that is, has type
         WRITE or
         APPENDpublic ProcessBuilder redirectOutput(ProcessBuilder.Redirect destination)
start()
 method send their standard output to this destination.
 If the destination is Redirect.PIPE
 (the initial value), then the standard output of a subprocess
 can be read using the input stream returned by Process.getInputStream().
 If the destination is set to any other value, then
 Process.getInputStream() will return a
 null input stream.
destination - the new standard output destinationIllegalArgumentException - if the redirect does not correspond to a valid
         destination of data, that is, has type
         READpublic ProcessBuilder redirectError(ProcessBuilder.Redirect destination)
start()
 method send their standard error to this destination.
 If the destination is Redirect.PIPE
 (the initial value), then the error output of a subprocess
 can be read using the input stream returned by Process.getErrorStream().
 If the destination is set to any other value, then
 Process.getErrorStream() will return a
 null input stream.
 
If the redirectErrorStream
 attribute has been set true, then the redirection set
 by this method has no effect.
destination - the new standard error destinationIllegalArgumentException - if the redirect does not correspond to a valid
         destination of data, that is, has type
         READpublic ProcessBuilder redirectInput(File file)
This is a convenience method.  An invocation of the form
 redirectInput(file)
 behaves in exactly the same way as the invocation
 redirectInput
 (Redirect.from(file)).
file - the new standard input sourcepublic ProcessBuilder redirectOutput(File file)
This is a convenience method.  An invocation of the form
 redirectOutput(file)
 behaves in exactly the same way as the invocation
 redirectOutput
 (Redirect.to(file)).
file - the new standard output destinationpublic ProcessBuilder redirectError(File file)
This is a convenience method.  An invocation of the form
 redirectError(file)
 behaves in exactly the same way as the invocation
 redirectError
 (Redirect.to(file)).
file - the new standard error destinationpublic ProcessBuilder.Redirect redirectInput()
start()
 method obtain their standard input from this source.
 The initial value is Redirect.PIPE.public ProcessBuilder.Redirect redirectOutput()
start()
 method redirect their standard output to this destination.
 The initial value is Redirect.PIPE.public ProcessBuilder.Redirect redirectError()
start()
 method redirect their standard error to this destination.
 The initial value is Redirect.PIPE.public ProcessBuilder inheritIO()
This is a convenience method. An invocation of the form
 
 pb.inheritIO()
 
 behaves in exactly the same way as the invocation
   
 pb.redirectInput(Redirect.INHERIT)
   .redirectOutput(Redirect.INHERIT)
   .redirectError(Redirect.INHERIT)
 
 This gives behavior equivalent to most operating system
 command interpreters, or the standard C library function
 system().public boolean redirectErrorStream()
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.
redirectErrorStream propertypublic ProcessBuilder redirectErrorStream(boolean redirectErrorStream)
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.
redirectErrorStream - the new property valuepublic Process start() throws IOException
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.
A minimal set of system dependent environment variables may
 be required to start a process on some operating systems.
 As a result, the subprocess may inherit additional environment variable
 settings beyond those in the process builder's environment().
 
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:
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.
Process object for managing the subprocessNullPointerException - if an element of the command list is nullIndexOutOfBoundsException - if the command is an empty list (has size 0)SecurityException - if a security manager exists and
         checkExec
         method doesn't allow creation of the subprocess, or
         checkRead method
         denies read access to the file, or
         checkWrite method
         denies write access to the file
         IOException - if an I/O error occursRuntime.exec(String[], String[], java.io.File) Submit a bug or feature 
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
 Copyright © 1993, 2025, Oracle and/or its affiliates.  All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.