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Java : ProcessBuilder with Examples

May 20, 2023 March 3, 2023

ProcessBuilder (Java SE 19 & JDK 19) API Examples.
You will find code examples on most ProcessBuilder methods.


Summary

This class is used to create operating system processes.

ProcessBuilder (Java SE 19 & JDK 19)

Class diagram

An example of starting Notepad on Windows.

final var builder = new ProcessBuilder("notepad");
final var process = builder.start();
System.out.println(process); // Process[pid=14796, exitValue="not exited"]

final var ret = process.waitFor();
System.out.println(ret); // 0

　↓

Notepad


Constructors

ProcessBuilder (String... command)

Constructs a process builder with the specified operating system program and arguments.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("exec : start");
        System.out.println("  args : " + Arrays.toString(args));
        System.out.println("exec : end");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var builder = new ProcessBuilder("java", "Exec", "aaa", "bbb");
        final var process = builder.start();
        try (final var reader = process.inputReader()) {
            reader.lines().forEach(System.out::println);
        }
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//exec : start
//  args : [aaa, bbb]
//exec : end
//waitFor : 0
//main : end

ProcessBuilder (List<String> command)

Constructs a process builder with the specified operating system program and arguments.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("exec : start");
        System.out.println("  args : " + Arrays.toString(args));
        System.out.println("exec : end");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var command = List.of("java", "Exec", "aaa", "bbb");
        final var builder = new ProcessBuilder(command);
        final var process = builder.start();
        try (final var reader = process.inputReader()) {
            reader.lines().forEach(System.out::println);
        }
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//exec : start
//  args : [aaa, bbb]
//exec : end
//waitFor : 0
//main : end

Methods

List<String> command ()

Returns this process builder's operating system program and arguments.

ProcessBuilder (Java SE 19 & JDK 19)

Please see also : command(String... command), command(List<String> command)

final var builder = new ProcessBuilder();
System.out.println(builder.command()); // []

builder.command("java", "Main");
System.out.println(builder.command()); // [java, Main]

ProcessBuilder command (String... command)

Sets this process builder's operating system program and arguments.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("exec : start");
        System.out.println("  args : " + Arrays.toString(args));
        System.out.println("exec : end");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var builder = new ProcessBuilder();
        final var process = builder.command("java", "Exec", "aaa", "bbb").start();
        try (final var reader = process.inputReader()) {
            reader.lines().forEach(System.out::println);
        }
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//exec : start
//  args : [aaa, bbb]
//exec : end
//waitFor : 0
//main : end

ProcessBuilder command (List<String> command)

Sets this process builder's operating system program and arguments.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("exec : start");
        System.out.println("  args : " + Arrays.toString(args));
        System.out.println("exec : end");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var command = List.of("java", "Exec", "aaa", "bbb");

        final var builder = new ProcessBuilder();
        final var process = builder.command(command).start();
        try (final var reader = process.inputReader()) {
            reader.lines().forEach(System.out::println);
        }
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//exec : start
//  args : [aaa, bbb]
//exec : end
//waitFor : 0
//main : end

File directory ()

Returns this process builder's working directory.

ProcessBuilder (Java SE 19 & JDK 19)

Please see also : directory(File directory)

final var dir = Path.of("R:", "java-work", "dir");
System.out.println(dir); // R:\java-work\dir

final var builder = new ProcessBuilder();
System.out.println(builder.directory()); // null

builder.directory(dir.toFile());
System.out.println(builder.directory()); // R:\java-work\dir

ProcessBuilder directory (File directory)

Sets this process builder's working directory.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("exec : start");
        System.out.println("  user.dir=" + System.getProperty("user.dir"));
        System.out.println("exec : end");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var dir = Path.of("R:", "java-work", "dir");

        final var builder = new ProcessBuilder("java", "Exec");
        final var process = builder.directory(dir.toFile()).start();
        try (final var reader = process.inputReader()) {
            reader.lines().forEach(System.out::println);
        }
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// --- PowerShell ---
//PS R:\java-work> tree /F
//...
//R:.
//│  Main.class
//│  Main.java
//│
//└─dir
//        Exec.class
//        Exec.java
//
//PS R:\java-work> java Main
//main : start
//exec : start
//  user.dir=R:\java-work\dir
//exec : end
//waitFor : 0
//main : end

Map<String,String> environment ()

Returns a string map view of this process builder's environment.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("exec : start");
        System.out.println("  env1=" + System.getenv("env1"));
        System.out.println("  env2=" + System.getenv("env2"));
        System.out.println("  env3=" + System.getenv("env3"));
        System.out.println("exec : end");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var builder = new ProcessBuilder("java", "Exec");
        final var env = builder.environment();
        env.put("env1", "aaa");
        env.put("env2", "bbb");
        env.put("env3", "ccc");

        final var process = builder.start();
        try (final var reader = process.inputReader()) {
            reader.lines().forEach(System.out::println);
        }
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//exec : start
//  env1=aaa
//  env2=bbb
//  env3=ccc
//exec : end
//waitFor : 0
//main : end

Please see also : System.getenv

final var builder = new ProcessBuilder();
final var env = builder.environment();
System.out.println(env.size()); // 45
System.out.println(env.get("OS")); // Windows_NT
System.out.println(env.get("PUBLIC")); // C:\Users\Public

ProcessBuilder inheritIO ()

Sets the source and destination for subprocess standard I/O to be the same as those of the current Java process.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("  OUT 1");
        System.err.println("  ERR 1");
        System.out.println("  OUT 2");
        System.err.println("  ERR 2");

        final var sc = new Scanner(System.in);
        while (sc.hasNext()) {
            final var next = sc.next();

            if ("quit".equals(next)) {
                System.out.println("  Quit!");
                break;
            }

            System.out.println("  next : " + next);
        }
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var builder = new ProcessBuilder("java", "Exec");
        final var process = builder.inheritIO().start();
        try (final var reader = process.inputReader()) {
            reader.lines().forEach(System.out::println);
        }
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//  OUT 1
//  ERR 1
//  OUT 2
//  ERR 2
//
//<Input> abcd
//  next : abcd
//<Input> 1234
//  next : 1234
//<Input> quit
//  Quit!
//
//waitFor : 0
//main : end

ProcessBuilder.Redirect redirectError ()

Returns this process builder's standard error destination.

ProcessBuilder (Java SE 19 & JDK 19)

Please see also : redirectError(ProcessBuilder.Redirect destination), redirectError(File file)

final var builder = new ProcessBuilder();
System.out.println(builder.redirectError()); // PIPE

builder.redirectError(ProcessBuilder.Redirect.INHERIT);
System.out.println(builder.redirectError()); // INHERIT

final var file = Path.of("aaa.txt");
builder.redirectError(file.toFile());
System.out.println(builder.redirectError()); // redirect to write to file "aaa.txt"

ProcessBuilder redirectError (File file)

Sets this process builder's standard error destination to a file.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("OUT 1");
        System.err.println("ERR 1");
        System.out.println("OUT 2");
        System.err.println("ERR 2");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var file = Path.of("aaa.txt");

        final var builder = new ProcessBuilder("java", "Exec");
        final var process = builder.redirectError(file.toFile()).start();
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//waitFor : 0
//main : end
//
//> cat aaa.txt
//ERR 1
//ERR 2

ProcessBuilder redirectError (ProcessBuilder.Redirect destination)

Sets this process builder's standard error destination.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("  OUT 1");
        System.err.println("  ERR 1");
        System.out.println("  OUT 2");
        System.err.println("  ERR 2");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var builder = new ProcessBuilder("java", "Exec");
        final var process = builder.redirectError(ProcessBuilder.Redirect.INHERIT).start();
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//  ERR 1
//  ERR 2
//waitFor : 0
//main : end

boolean redirectErrorStream ()

Tells whether this process builder merges standard error and standard output.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("  OUT 1");
        System.err.println("  ERR 1");
        System.out.println("  OUT 2");
        System.err.println("  ERR 2");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var builder = new ProcessBuilder("java", "Exec");

        if (args.length == 1 && "merge".equals(args[0])) {
            builder.redirectErrorStream(true);
        }
        System.out.println("redirect error stream : " + builder.redirectErrorStream());

        final var process = builder.start();
        try (final var reader = process.inputReader()) {
            reader.lines().forEach(System.out::println);
        }
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//redirect error stream : false
//  OUT 1
//  OUT 2
//waitFor : 0
//main : end
//
//> java Main merge
//main : start
//redirect error stream : true
//  OUT 1
//  ERR 1
//  OUT 2
//  ERR 2
//waitFor : 0
//main : end

ProcessBuilder redirectErrorStream (boolean redirectErrorStream)

Sets this process builder's redirectErrorStream property.

ProcessBuilder (Java SE 19 & JDK 19)

Please see redirectErrorStream().

ProcessBuilder.Redirect redirectInput ()

Returns this process builder's standard input source.

ProcessBuilder (Java SE 19 & JDK 19)

Please see also : redirectInput(ProcessBuilder.Redirect source), redirectInput(File file)

final var builder = new ProcessBuilder();
System.out.println(builder.redirectInput()); // PIPE

builder.redirectInput(ProcessBuilder.Redirect.INHERIT);
System.out.println(builder.redirectInput()); // INHERIT

final var file = Path.of("aaa.txt");
builder.redirectInput(file.toFile());
System.out.println(builder.redirectInput()); // redirect to read from file "aaa.txt"

ProcessBuilder redirectInput (File file)

Sets this process builder's standard input source to a file.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) throws IOException {
        System.out.println("exec : start");

        final var sc = new Scanner(System.in);
        while (sc.hasNext()) {
            final var next = sc.next();

            if ("quit".equals(next)) {
                System.out.println("  Quit!");
                break;
            }

            System.out.println("  next : " + next);
        }

        System.out.println("exec : end");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var file = Path.of("aaa.txt");
        Files.writeString(file, """
                abcd
                1234
                quit
                """);

        final var builder = new ProcessBuilder("java", "Exec");
        final var process = builder.redirectInput(file.toFile()).start();
        try (final var reader = process.inputReader()) {
            reader.lines().forEach(System.out::println);
        }
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//exec : start
//  next : abcd
//  next : 1234
//  Quit!
//exec : end
//waitFor : 0
//main : end

ProcessBuilder redirectInput (ProcessBuilder.Redirect source)

Sets this process builder's standard input source.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) throws IOException {
        System.out.println("exec : start");

        final var sc = new Scanner(System.in);
        while (sc.hasNext()) {
            final var next = sc.next();

            if ("quit".equals(next)) {
                System.out.println("  Quit!");
                break;
            }

            System.out.println("  next : " + next);
        }

        System.out.println("exec : end");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var builder = new ProcessBuilder("java", "Exec");
        final var process = builder.redirectInput(ProcessBuilder.Redirect.INHERIT).start();
        try (final var reader = process.inputReader()) {
            reader.lines().forEach(System.out::println);
        }
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//exec : start
//
//<Input> abcd
//  next : abcd
//<Input> 1234
//  next : 1234
//<Input> quit
//  Quit!
//
//exec : end
//waitFor : 0
//main : end

ProcessBuilder.Redirect redirectOutput ()

Returns this process builder's standard output destination.

ProcessBuilder (Java SE 19 & JDK 19)

Please see also : redirectOutput(ProcessBuilder.Redirect destination), redirectOutput(File file)

final var builder = new ProcessBuilder();
System.out.println(builder.redirectOutput()); // PIPE

builder.redirectOutput(ProcessBuilder.Redirect.INHERIT);
System.out.println(builder.redirectOutput()); // INHERIT

final var file = Path.of("aaa.txt");
builder.redirectOutput(file.toFile());
System.out.println(builder.redirectOutput()); // redirect to write to file "aaa.txt"

ProcessBuilder redirectOutput (File file)

Sets this process builder's standard output destination to a file.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("OUT 1");
        System.err.println("ERR 1");
        System.out.println("OUT 2");
        System.err.println("ERR 2");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var file = Path.of("aaa.txt");

        final var builder = new ProcessBuilder("java", "Exec");
        final var process = builder.redirectOutput(file.toFile()).start();
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//waitFor : 0
//main : end
//
//> cat aaa.txt
//OUT 1
//OUT 2

ProcessBuilder redirectOutput (ProcessBuilder.Redirect destination)

Sets this process builder's standard output destination.

ProcessBuilder (Java SE 19 & JDK 19) 
public class Exec {
    public static void main(String[] args) {
        System.out.println("  OUT 1");
        System.err.println("  ERR 1");
        System.out.println("  OUT 2");
        System.err.println("  ERR 2");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var builder = new ProcessBuilder("java", "Exec");
        final var process = builder.redirectOutput(ProcessBuilder.Redirect.INHERIT).start();
        System.out.println("waitFor : " + process.waitFor());

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//  OUT 1
//  OUT 2
//waitFor : 0
//main : end

Process start ()

Starts a new process using the attributes of this process builder.

ProcessBuilder (Java SE 19 & JDK 19)

Please see ProcessBuilder(String... command).

static List<Process> startPipeline (List<ProcessBuilder> builders)

Starts a Process for each ProcessBuilder, creating a pipeline of processes linked by their standard output and standard input streams.

ProcessBuilder (Java SE 19 & JDK 19) 
public class ExecA {
    public static void main(String[] args) {
        System.out.println("abcd");
        System.out.println("1234");
        System.out.println("quit");
    }
}

public class ExecB {
    public static void main(String[] args) {
        System.out.println("exec B : start");

        final var sc = new Scanner(System.in);
        while (sc.hasNext()) {
            final var next = sc.next();

            if ("quit".equals(next)) {
                System.out.println("  Quit!");
                break;
            }

            System.out.println("  next : " + next);
        }

        System.out.println("exec B : end");
    }
}

public class Main {
    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("main : start");

        final var file = Path.of("bbb.txt");

        final var builders = List.of(
                new ProcessBuilder("java", "ExecA"),
                new ProcessBuilder("java", "ExecB").redirectOutput(file.toFile())
        );

        final var processes = ProcessBuilder.startPipeline(builders);
        for (final var process : processes) {
            System.out.println("waitFor : " + process.waitFor());
        }

        System.out.println("main : end");
    }
}

// Result
// ↓
//> java Main
//main : start
//waitFor : 0
//waitFor : 0
//main : end
//
//> cat bbb.txt
//exec B : start
//  next : abcd
//  next : 1234
//  Quit!
//exec B : end

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