scala.sys.process

# ProcessBuilder

#### trait ProcessBuilder extends Source with Sink

Represents a sequence of one or more external processes that can be executed. A `ProcessBuilder` can be a single external process, or a combination of other `ProcessBuilder`. One can control where a the output of an external process will go to, and where its input will come from, or leave that decision to whoever starts it.

One creates a `ProcessBuilder` through factories provided in scala.sys.process.Process's companion object, or implicit conversions based on these factories made available in the package object scala.sys.process. Here are some examples:

    import scala.sys.process._

    // Executes "ls" and sends output to stdout
    "ls".!

    // Execute "ls" and assign a `Stream[String]` of its output to "contents".
    val contents = Process("ls").lineStream

    // Here we use a `Seq` to make the parameter whitespace-safe
    def contentsOf(dir: String): String = Seq("ls", dir).!!

The methods of `ProcessBuilder` are divided in three categories: the ones that combine two `ProcessBuilder` to create a third, the ones that redirect input or output of a `ProcessBuilder`, and the ones that execute the external processes associated with it.

#### Combining `ProcessBuilder`

Two existing `ProcessBuilder` can be combined in the following ways:

- They can be executed in parallel, with the output of the first being fed as input to the second, like Unix pipes. This is achieved with the `#|` method.
- They can be executed in sequence, with the second starting as soon as the first ends. This is done by the `###` method.
- The execution of the second one can be conditioned by the return code (exit status) of the first, either only when it's zero, or only when it's not zero. The methods `#&&` and `#||` accomplish these tasks.

#### Redirecting Input/Output

Though control of input and output can be done when executing the process, there's a few methods that create a new `ProcessBuilder` with a pre-configured input or output. They are `#<`, `#>` and `#>>`, and may take as input either another `ProcessBuilder` (like the pipe described above), or something else such as a `java.io.File` or a `java.io.InputStream`. For example:

    new URL("http://databinder.net/dispatch/About") #> "grep JSON" #>> new File("About_JSON") !

#### Starting Processes

To execute all external commands associated with a `ProcessBuilder`, one may use one of four groups of methods. Each of these methods have various overloads and variations to enable further control over the I/O. These methods are:

- `run`: the most general method, it returns a scala.sys.process.Process immediately, and the external command executes concurrently.
- `!`: blocks until all external commands exit, and returns the exit code of the last one in the chain of execution.
- `!!`: blocks until all external commands exit, and returns a `String` with the output generated.
- `lineStream`: returns immediately like `run`, and the output being generated is provided through a `Stream[String]`. Getting the next element of that `Stream` may block until it becomes available. This method will throw an exception if the return code is different than zero -- if this is not desired, use the `lineStream_!` method.

#### Handling Input and Output

If not specified, the input of the external commands executed with `run` or `!` will not be tied to anything, and the output will be redirected to the stdout and stderr of the Scala process. For the methods `!!` and `lines`, no input will be provided, and the output will be directed according to the semantics of these methods.

Some methods will cause stdin to be used as input. Output can be controlled with a scala.sys.process.ProcessLogger -- `!!` and `lines` will only redirect error output when passed a `ProcessLogger`. If one desires full control over input and output, then a scala.sys.process.ProcessIO can be used with `run`.

For example, we could silence the error output from `lines_!` like this:

    val etcFiles = "find /etc" lines_! ProcessLogger(line => ())

#### Extended Example

Let's examine in detail one example of usage:

    import scala.sys.process._
    "find src -name *.scala -exec grep null {} ;"  #|  "xargs test -z"  #&&  "echo null-free"  #||  "echo null detected"  !

Note that every `String` is implicitly converted into a `ProcessBuilder` through the implicits imported from scala.sys.process. These `ProcessBuilder` are then combined in three different ways.

1. `#|` pipes the output of the first command into the input of the second command. It mirrors a shell pipe (`|`).
2. `#&&` conditionally executes the second command if the previous one finished with exit value 0. It mirrors shell's `&&`.
3. `#||` conditionally executes the third command if the exit value of the previous command is different than zero. It mirrors shell's `||`.

Finally, `!` at the end executes the commands, and returns the exit value. Whatever is printed will be sent to the Scala process standard output. If we wanted to capture it, we could run that with `!!` instead.

Note: though it is not shown above, the equivalent of a shell's `;` would be `###`. The reason for this name is that `;` is a reserved token in Scala.

Note: the `lines` method, though deprecated, may conflict with the `StringLike` method of the same name. To avoid this, one may wish to call the builders in `Process` instead of importing `scala.sys.process._`. The example above would be

    import scala.sys.process.Process
    Process("find src -name *.scala -exec grep null {} ;") #| Process("xargs test -z") #&& Process("echo null-free") #|| Process("echo null detected") !

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3. Source
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### Abstract Value Members

1. #### abstract def !(log: ProcessLogger): Int

   Starts the process represented by this builder, blocks until it exits, and returns the exit code.

   Starts the process represented by this builder, blocks until it exits, and returns the exit code. Standard output and error are sent to the given ProcessLogger.

2. #### abstract def !: Int

   Starts the process represented by this builder, blocks until it exits, and returns the exit code.

   Starts the process represented by this builder, blocks until it exits, and returns the exit code. Standard output and error are sent to the console.

3. #### abstract def !!(log: ProcessLogger): String

   Starts the process represented by this builder, blocks until it exits, and returns the output as a String.

   Starts the process represented by this builder, blocks until it exits, and returns the output as a String. Standard error is sent to the provided ProcessLogger. If the exit code is non-zero, an exception is thrown.

4. #### abstract def !!: String

   Starts the process represented by this builder, blocks until it exits, and returns the output as a String.

   Starts the process represented by this builder, blocks until it exits, and returns the output as a String. Standard error is sent to the console. If the exit code is non-zero, an exception is thrown.

5. #### abstract def !!<(log: ProcessLogger): String

   Starts the process represented by this builder, blocks until it exits, and returns the output as a String.

   Starts the process represented by this builder, blocks until it exits, and returns the output as a String. Standard error is sent to the provided ProcessLogger. If the exit code is non-zero, an exception is thrown. The newly started process reads from standard input of the current process.

6. #### abstract def !!<: String

   Starts the process represented by this builder, blocks until it exits, and returns the output as a String.

   Starts the process represented by this builder, blocks until it exits, and returns the output as a String. Standard error is sent to the console. If the exit code is non-zero, an exception is thrown. The newly started process reads from standard input of the current process.

7. #### abstract def !<(log: ProcessLogger): Int

   Starts the process represented by this builder, blocks until it exits, and returns the exit code.

   Starts the process represented by this builder, blocks until it exits, and returns the exit code. Standard output and error are sent to the given ProcessLogger. The newly started process reads from standard input of the current process.

8. #### abstract def !<: Int

   Starts the process represented by this builder, blocks until it exits, and returns the exit code.

   Starts the process represented by this builder, blocks until it exits, and returns the exit code. Standard output and error are sent to the console. The newly started process reads from standard input of the current process.

9. #### abstract def ###(other: ProcessBuilder): ProcessBuilder

   Constructs a command that will run this command and then `other`.

   Constructs a command that will run this command and then `other`. The exit code will be the exit code of `other`.

10. #### abstract def #&&(other: ProcessBuilder): ProcessBuilder

    Constructs a command that runs this command first and then `other` if this command succeeds.

11. #### abstract def #|(other: ProcessBuilder): ProcessBuilder

    Constructs a command that will run this command and pipes the output to `other`.

    Constructs a command that will run this command and pipes the output to `other`. `other` must be a simple command.

12. #### abstract def #||(other: ProcessBuilder): ProcessBuilder

    Constructs a command that runs this command first and then `other` if this command does not succeed.

13. #### abstract def canPipeTo: Boolean

    True if this command can be the target of a pipe.

14. #### abstract def hasExitValue: Boolean

    True if this command has an exit code which should be propagated to the user.

    True if this command has an exit code which should be propagated to the user. Given a pipe between A and B, if B.hasExitValue is true then the exit code will be the one from B; if it is false, the one from A. This exists to prevent output redirections (implemented as pipes) from masking useful process error codes.

15. #### abstract def lineStream(log: ProcessLogger): Stream[String]

    Starts the process represented by this builder.

    Starts the process represented by this builder. The output is returned as a Stream that blocks when lines are not available but the process has not completed. Standard error is sent to the provided ProcessLogger. If the process exits with a non-zero value, the Stream will provide all lines up to termination and then throw an exception.

16. #### abstract def lineStream: Stream[String]

    Starts the process represented by this builder.

    Starts the process represented by this builder. The output is returned as a Stream that blocks when lines are not available but the process has not completed. Standard error is sent to the console. If the process exits with a non-zero value, the Stream will provide all lines up to termination and then throw an exception.

17. #### abstract def lineStream_!(log: ProcessLogger): Stream[String]

    Starts the process represented by this builder.

    Starts the process represented by this builder. The output is returned as a Stream that blocks when lines are not available but the process has not completed. Standard error is sent to the provided ProcessLogger. If the process exits with a non-zero value, the Stream will provide all lines up to termination but will not throw an exception.

18. #### abstract def lineStream_!: Stream[String]

    Starts the process represented by this builder.

    Starts the process represented by this builder. The output is returned as a Stream that blocks when lines are not available but the process has not completed. Standard error is sent to the console. If the process exits with a non-zero value, the Stream will provide all lines up to termination but will not throw an exception.

19. #### abstract def run(log: ProcessLogger, connectInput: Boolean): Process

    Starts the process represented by this builder, blocks until it exits, and returns the exit code.

    Starts the process represented by this builder, blocks until it exits, and returns the exit code. Standard output and error are sent to the given ProcessLogger. The newly started process reads from standard input of the current process if `connectInput` is true.

20. #### abstract def run(connectInput: Boolean): Process

    Starts the process represented by this builder.

    Starts the process represented by this builder. Standard output and error are sent to the console. The newly started process reads from standard input of the current process if `connectInput` is true.

21. #### abstract def run(io: ProcessIO): Process

    Starts the process represented by this builder.

    Starts the process represented by this builder. I/O is handled by the given ProcessIO instance.

22. #### abstract def run(log: ProcessLogger): Process

    Starts the process represented by this builder.

    Starts the process represented by this builder. Standard output and error are sent to the given ProcessLogger.

23. #### abstract def run(): Process

    Starts the process represented by this builder.

    Starts the process represented by this builder. Standard output and error are sent to the console.

24. #### abstract def toSink: ProcessBuilder

    Attributes
      protected
    Definition Classes
      Sink

25. #### abstract def toSource: ProcessBuilder

    Attributes
      protected
    Definition Classes
      Source

### Concrete Value Members

1. #### final def !=(arg0: Any): Boolean

   Definition Classes
     AnyRef → Any

2. #### final def ##(): Int

   Definition Classes
     AnyRef → Any

3. #### def #<(b: ProcessBuilder): ProcessBuilder

   Reads the output of a scala.sys.process.ProcessBuilder into the input stream of this process.

   Reads the output of a scala.sys.process.ProcessBuilder into the input stream of this process.

   Definition Classes
     Sink

4. #### def #<(in: ⇒ InputStream): ProcessBuilder

   Reads the given InputStream into the input stream of this process.

   Reads the given InputStream into the input stream of this process. The argument is call-by-name, so the stream is recreated, read, and closed each time this process is executed.

   Definition Classes
     Sink

5. #### def #<(f: URL): ProcessBuilder

   Reads the given URL into the input stream of this process.

   Reads the given URL into the input stream of this process.

   Definition Classes
     Sink

6. #### def #<(f: File): ProcessBuilder

   Reads the given file into the input stream of this process.

   Reads the given file into the input stream of this process.

   Definition Classes
     Sink

7. #### def #>(b: ProcessBuilder): ProcessBuilder

   Writes the output stream of this process to a scala.sys.process.ProcessBuilder.

   Writes the output stream of this process to a scala.sys.process.ProcessBuilder.

   Definition Classes
     Source

8. #### def #>(out: ⇒ OutputStream): ProcessBuilder

   Writes the output stream of this process to the given OutputStream.

   Writes the output stream of this process to the given OutputStream. The argument is call-by-name, so the stream is recreated, written, and closed each time this process is executed.

   Definition Classes
     Source

9. #### def #>(f: File): ProcessBuilder

   Writes the output stream of this process to the given file.

   Writes the output stream of this process to the given file.

   Definition Classes
     Source

10. #### def #>>(f: File): ProcessBuilder

    Appends the output stream of this process to the given file.

    Appends the output stream of this process to the given file.

    Definition Classes
      Source

11. #### def +(other: String): String

    Implicit information
      This member is added by an implicit conversion from ProcessBuilder to any2stringadd[ProcessBuilder] performed by method any2stringadd in scala.Predef.
    Definition Classes
      any2stringadd

12. #### def ->[B](y: B): (ProcessBuilder, B)

    Implicit information
      This member is added by an implicit conversion from ProcessBuilder to ArrowAssoc[ProcessBuilder] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc
    Annotations
      @inline()

13. #### final def ==(arg0: Any): Boolean

    Definition Classes
      AnyRef → Any

14. #### final def asInstanceOf[T0]: T0

    Definition Classes
      Any

15. #### def cat: ProcessBuilder

    Returnes a scala.sys.process.ProcessBuilder representing this `Source`.

    Returnes a scala.sys.process.ProcessBuilder representing this `Source`.

    Definition Classes
      Source

16. #### def clone(): AnyRef

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

17. #### def ensuring(cond: (ProcessBuilder) ⇒ Boolean, msg: ⇒ Any): ProcessBuilder

    Implicit information
      This member is added by an implicit conversion from ProcessBuilder to Ensuring[ProcessBuilder] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

18. #### def ensuring(cond: (ProcessBuilder) ⇒ Boolean): ProcessBuilder

    Implicit information
      This member is added by an implicit conversion from ProcessBuilder to Ensuring[ProcessBuilder] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

19. #### def ensuring(cond: Boolean, msg: ⇒ Any): ProcessBuilder

    Implicit information
      This member is added by an implicit conversion from ProcessBuilder to Ensuring[ProcessBuilder] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

20. #### def ensuring(cond: Boolean): ProcessBuilder

    Implicit information
      This member is added by an implicit conversion from ProcessBuilder to Ensuring[ProcessBuilder] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

21. #### final def eq(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

22. #### def equals(arg0: Any): Boolean

    Definition Classes
      AnyRef → Any

23. #### def finalize(): Unit

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )

24. #### def formatted(fmtstr: String): String

    Returns string formatted according to given `format` string.

    Returns string formatted according to given `format` string. Format strings are as for `String.format` (@see java.lang.String.format).

    Implicit information
      This member is added by an implicit conversion from ProcessBuilder to StringFormat[ProcessBuilder] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()

25. #### final def getClass(): Class[_]

    Definition Classes
      AnyRef → Any

26. #### def hashCode(): Int

    Definition Classes
      AnyRef → Any

27. #### final def isInstanceOf[T0]: Boolean

    Definition Classes
      Any

28. #### final def ne(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

29. #### final def notify(): Unit

    Definition Classes
      AnyRef

30. #### final def notifyAll(): Unit

    Definition Classes
      AnyRef

31. #### final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
      AnyRef

32. #### def toString(): String

    Definition Classes
      AnyRef → Any

33. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

34. #### final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

35. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

36. #### def →[B](y: B): (ProcessBuilder, B)

    Implicit information
      This member is added by an implicit conversion from ProcessBuilder to ArrowAssoc[ProcessBuilder] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Deprecated Value Members

1. #### def lines(log: ProcessLogger): Stream[String]

   Deprecated (renamed).

   Deprecated (renamed). Use `lineStream(log: ProcessLogger)` instead.

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use stream instead.

2. #### def lines: Stream[String]

   Deprecated (renamed).

   Deprecated (renamed). Use `lineStream` instead.

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use lineStream instead.

3. #### def lines_!(log: ProcessLogger): Stream[String]

   Deprecated (renamed).

   Deprecated (renamed). Use `lineStream_!(log: ProcessLogger)` instead.

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use stream_! instead.

4. #### def lines_!: Stream[String]

   Deprecated (renamed).

   Deprecated (renamed). Use `lineStream_!` instead.

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use lineStream_! instead.

### Inherited from Sink

### Inherited from Source

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from ProcessBuilder to any2stringadd[ProcessBuilder]

### Inherited by implicit conversion StringFormat from ProcessBuilder to StringFormat[ProcessBuilder]

### Inherited by implicit conversion Ensuring from ProcessBuilder to Ensuring[ProcessBuilder]

### Inherited by implicit conversion ArrowAssoc from ProcessBuilder to ArrowAssoc[ProcessBuilder]

### Ungrouped