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Standard library for the Scala Programming Language
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.sys
package process
import processInternal._
import ProcessBuilder._
/** 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".
* // Because [[scala.Predef]] already defines a `lines` method for `String`,
* // we use [[scala.sys.process.Process]]'s object companion to create it.
* val contents = Process("ls").lines
*
* // 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.lang.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.
* * `lines`: returns immediately like `run`, and the output being generared
* 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 `lines_!` 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 (`|`).
* 1. `#&&` conditionally executes the second command if the previous one finished with
* exit value 0. It mirrors shell's `&&`.
* 1. `#||` 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 caputre 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.
*/
trait ProcessBuilder extends Source with Sink {
/** 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.
*/
def !! : 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.
*/
def !!(log: ProcessLogger): 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.
*/
def !!< : 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.
*/
def !!<(log: ProcessLogger): String
/** 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.
*/
def lines: Stream[String]
/** 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.
*/
def lines(log: ProcessLogger): Stream[String]
/** 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.
*/
def lines_! : Stream[String]
/** 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.
*/
def lines_!(log: ProcessLogger): Stream[String]
/** 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.
*/
def ! : Int
/** 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.
*/
def !(log: ProcessLogger): Int
/** 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.
*/
def !< : Int
/** 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.
*/
def !<(log: ProcessLogger): Int
/** Starts the process represented by this builder. Standard output and error
* are sent to the console.*/
def run(): Process
/** Starts the process represented by this builder. Standard output and error
* are sent to the given ProcessLogger.
*/
def run(log: ProcessLogger): Process
/** Starts the process represented by this builder. I/O is handled by the
* given ProcessIO instance.
*/
def run(io: ProcessIO): Process
/** 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.
*/
def run(connectInput: Boolean): Process
/** 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.
*/
def run(log: ProcessLogger, connectInput: Boolean): Process
/** Constructs a command that runs this command first and then `other` if this
* command succeeds.
*/
def #&& (other: ProcessBuilder): ProcessBuilder
/** Constructs a command that runs this command first and then `other` if this
* command does not succeed.
*/
def #|| (other: ProcessBuilder): ProcessBuilder
/** Constructs a command that will run this command and pipes the output to
* `other`. `other` must be a simple command.
*/
def #| (other: ProcessBuilder): ProcessBuilder
/** Constructs a command that will run this command and then `other`. The
* exit code will be the exit code of `other`.
*/
def ### (other: ProcessBuilder): ProcessBuilder
/** True if this command can be the target of a pipe. */
def canPipeTo: Boolean
/** 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.
*/
def hasExitValue: Boolean
}
/** This object contains traits used to describe input and output sources. */
object ProcessBuilder extends ProcessBuilderImpl {
/** Used when creating [[scala.sys.process.ProcessBuilder.Source]] from an URL. */
trait URLBuilder extends Source {
}
/** Used when creating [[scala.sys.process.ProcessBuilder.Source]] and/or
* [[scala.sys.process.ProcessBuilder.Sink]] from a file.
*/
trait FileBuilder extends Sink with Source {
/** Append the contents of a `java.io.File` to this file */
def #<<(f: File): ProcessBuilder
/** Append the contents from a `java.net.URL` to this file */
def #<<(u: URL): ProcessBuilder
/** Append the contents of a `java.io.InputStream` to this file */
def #<<(i: => InputStream): ProcessBuilder
/** Append the contents of a [[scala.sys.process.ProcessBuilder]] to this file */
def #<<(p: ProcessBuilder): ProcessBuilder
}
/** Represents everything that can be used as an input to a
* [[scala.sys.process.ProcessBuilder]].
*/
trait Source {
protected def toSource: ProcessBuilder
/** Writes the output stream of this process to the given file. */
def #> (f: File): ProcessBuilder = toFile(f, false)
/** Appends the output stream of this process to the given file. */
def #>> (f: File): ProcessBuilder = toFile(f, true)
/** 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.
*/
def #>(out: => OutputStream): ProcessBuilder = #> (new OStreamBuilder(out, "