Document the usage and methods of scala.sys.process.

From the first international scaladoc marathon.

   Contributed by: Daniel Sobral

git-svn-id: http://lampsvn.epfl.ch/svn-repos/scala/scala/trunk@25599 5e8d7ff9-d8ef-0310-90f0-a4852d11357a

src/library/scala/sys/process/BasicIO.scala

@@ -14,6 +14,12 @@ import java.io.{ BufferedReader, InputStreamReader, FilterInputStream, FilterOut
 import java.util.concurrent.LinkedBlockingQueue
 import scala.collection.immutable.Stream
 
+/**
+  * This object contains factories for [[scala.sys.process.ProcessIO]],
+  * which can be used to control the I/O of a [[scala.sys.process.Process]]
+  * when a [[scala.sys.process.ProcessBuilder]] is started with the `run`
+  * command.
+  */
 object BasicIO {
   final val BufferSize = 8192
   final val Newline    = props("line.separator")

src/library/scala/sys/process/Process.scala

@@ -14,6 +14,19 @@ import ProcessBuilder._
 
 /** Represents a process that is running or has finished running.
  *  It may be a compound process with several underlying native processes (such as 'a #&& b`).
+ *
+ *  This trait is often not used directly, though its companion object contains
+ *  factories for [[scala.sys.process.ProcessBuilder]], the main component of this
+ *  package.
+ *
+ *  It is used directly when calling the method `run` on a `ProcessBuilder`,
+ *  which makes the process run in the background. The methods provided on `Process`
+ *  make it possible for one to block until the process exits and get the exit value,
+ *  or destroy the process altogether.
+ *
+ *  Presently, one cannot poll the `Process` to see if it has finished.
+ *
+ *  @see [[scala.sys.process.ProcessBuilder]]
  */
 trait Process {
   /** Blocks until this process exits and returns the exit code.*/
@@ -25,20 +38,52 @@ trait Process {
 /** Methods for constructing simple commands that can then be combined. */
 object Process extends ProcessImpl with ProcessCreation { }
 
+/** Factories for creating [[scala.sys.process.ProcessBuilder]]. They can be
+ *  found on and used through [[scala.sys.process.Process]]'s companion object.
+ */
 trait ProcessCreation {  
+  /** Create a [[scala.sys.process.ProcessBuilder]] from a `String`, including the 
+    * parameters.
+    *
+    * @example {{{ apply("cat file.txt") }}}
+    */ 
   def apply(command: String): ProcessBuilder                         = apply(command, None)
+  
+  /** Create a [[scala.sys.process.ProcessBuilder]] from a sequence of `String`,
+    * where the head is the command and each element of the tail is a parameter.
+    *
+    * @example {{{ apply("cat" :: files) }}}
+    */
   def apply(command: Seq[String]): ProcessBuilder                    = apply(command, None)
+  
+  /** Create a [[scala.sys.process.ProcessBuilder]] from a command represented by a `String`,
+    * and a sequence of `String` representing the arguments.
+    *
+    * @example {{{ apply("cat", files) }}}
+    */
   def apply(command: String, arguments: Seq[String]): ProcessBuilder = apply(command +: arguments, None)
 
-  /** create ProcessBuilder with working dir set to File and extra environment variables */
+  /** Create a [[scala.sys.process.ProcessBuilder]] with working dir set to `File` and extra 
+    * environment variables.
+    *
+    * @example {{{ apply("java", new java.ioFile("/opt/app"), "CLASSPATH" -> "library.jar") }}}
+    */
   def apply(command: String, cwd: File, extraEnv: (String, String)*): ProcessBuilder =
     apply(command, Some(cwd), extraEnv: _*)
 
-  /** create ProcessBuilder with working dir set to File and extra environment variables */
+  /** Create a [[scala.sys.process.ProcessBuilder]] with working dir set to `File` and extra 
+    * environment variables.
+    *
+    * @example {{{ apply("java" :: javaArgs, new java.ioFile("/opt/app"), "CLASSPATH" -> "library.jar") }}}
+    */
   def apply(command: Seq[String], cwd: File, extraEnv: (String, String)*): ProcessBuilder =
     apply(command, Some(cwd), extraEnv: _*)
 
-  /** create ProcessBuilder with working dir optionally set to File and extra environment variables */
+  /** Create a [[scala.sys.process.ProcessBuilder]] with working dir optionally set to 
+    * `File` and extra environment variables. 
+    *
+    * @example {{{ apply("java", params.get("cwd"), "CLASSPATH" -> "library.jar") }}}
+    */
   def apply(command: String, cwd: Option[File], extraEnv: (String, String)*): ProcessBuilder = {
     apply(command.split("""\s+"""), cwd, extraEnv : _*)
     // not smart to use this on windows, because CommandParser uses \ to escape ".
@@ -48,7 +93,11 @@ trait ProcessCreation {
     }*/
   }
 
-  /** create ProcessBuilder with working dir optionally set to File and extra environment variables */
+  /** Create a [[scala.sys.process.ProcessBuilder]] with working dir optionally set to
+    * `File` and extra environment variables.
+    *
+    * @example {{{ apply("java" :: javaArgs, params.get("cwd"), "CLASSPATH" -> "library.jar") }}}
+    */
   def apply(command: Seq[String], cwd: Option[File], extraEnv: (String, String)*): ProcessBuilder = {
     val jpb = new JProcessBuilder(command.toArray: _*)
     cwd foreach (jpb directory _)
@@ -56,30 +105,111 @@ trait ProcessCreation {
     apply(jpb)
   }
 
+  /** create a [[scala.sys.process.ProcessBuilder]] from a `java.lang.ProcessBuilder`.
+    *
+    * @example {{{ 
+    * apply((new java.lang.ProcessBuilder("ls", "-l")) directory new java.io.File(System.getProperty("user.home"))) 
+    * }}}
+    */
   def apply(builder: JProcessBuilder): ProcessBuilder = new Simple(builder)
+  
+  /** create a [[scala.sys.process.ProcessBuilder]] from a `java.io.File`. This
+    * `ProcessBuilder` can then be used as a `Source` or a `Sink`, so one can
+    * pipe things from and to it.
+    */
   def apply(file: File): FileBuilder                  = new FileImpl(file)
+  
+  /** Create a [[scala.sys.process.ProcessBuilder]] from a `java.net.URL`. This 
+    * `ProcessBuilder` can then be used as a `Source`, so that one can pipe things
+    * from it.
+    */
   def apply(url: URL): URLBuilder                     = new URLImpl(url)
+  
+  /** Create a [[scala.sys.process.ProcessBuilder]] from a Scala XML Element.
+    * This can be used as a way to template strings.
+    *
+    * @example {{{ 
+    * apply(<x> {dxPath.absolutePath} --dex --output={classesDexPath.absolutePath} {classesMinJarPath.absolutePath}</x>)
+    * }}}
+    */
   def apply(command: scala.xml.Elem): ProcessBuilder  = apply(command.text.trim)
+  
+  /** Create a [[scala.sys.process.ProcessBuilder]] from a `Boolean`. This can be
+    * to force an exit value.
+    */
   def apply(value: Boolean): ProcessBuilder           = apply(value.toString, if (value) 0 else 1)
   
+  /** Create a [[scala.sys.process.ProcessBuilder]] from a `String` name and a
+    * `Boolean`. This can be used to force an exit value, with the name being
+    * used for `toString`.
+    */
   def apply(name: String, exitValue: => Int): ProcessBuilder = new Dummy(name, exitValue)
+  
+  /** Create a sequence of [[scala.sys.process.ProcessBuilder.Source]] from a sequence of
+    * something else for which there's an implicit conversion to `Source`.
+    */
   def applySeq[T](builders: Seq[T])(implicit convert: T => Source): Seq[Source] = builders.map(convert)
 
+  /** Create a [[scala.sys.process.ProcessBuilder]] from one or more
+    * [[scala.sys.process.ProcessBuilder.Source]], which can then be
+    * piped to something else.
+    *
+    * This will concatenate the output of all sources.
+    */
   def cat(file: Source, files: Source*): ProcessBuilder = cat(file +: files)
+  
+  /** Create a [[scala.sys.process.ProcessBuilder]] from a non-empty sequence
+    * of [[scala.sys.process.ProcessBuilder.Source]], which can then be
+    * piped to something else.
+    *
+    * This will concatenate the output of all sources. For example:
+    *
+    * {{{
+    * import scala.sys.process._
+    * import scala.sys.process.Process.cat
+    * import java.net.URL
+    * import java.io.File
+    *
+    * val spde = new URL("http://technically.us/spde/About")
+    * val dispatch = new URL("http://databinder.net/dispatch/About")
+    * val build = new File("project/build.properties")
+    * cat(spde, dispatch, build) #| "grep -i scala" !
+    * }}}
+    */
   def cat(files: Seq[Source]): ProcessBuilder = {
     require(files.nonEmpty)
     files map (_.cat) reduceLeft (_ #&& _)
   }
 }
 
+/** Provide implicit conversions for the factories offered by [[scala.sys.process.Process]]'s
+  * companion object. These implicits can then be used to decrease the noise in a pipeline
+  * of commands, making it look more shell-like. They are available through the package object
+  * [[scala.sys.process]].
+  */
 trait ProcessImplicits {
   import Process._
   
+  /** Return a sequence of [[scala.sys.process.ProcessBuilder.Source]] from a sequence
+    * of values for which an implicit conversion to `Source` is available.
+    */
   implicit def buildersToProcess[T](builders: Seq[T])(implicit convert: T => Source): Seq[Source] = applySeq(builders)
+  
+  /** Implicitly convert a `java.lang.ProcessBuilder` into a Scala one. */
   implicit def builderToProcess(builder: JProcessBuilder): ProcessBuilder = apply(builder)
+  
+  /** Implicitly convert a `java.io.File` into a [[scala.sys.process.ProcessBuilder]] */ 
   implicit def fileToProcess(file: File): FileBuilder                     = apply(file)
+  
+  /** Implicitly convert a `java.net.URL` into a [[scala.sys.process.ProcessBuilder]] */
   implicit def urlToProcess(url: URL): URLBuilder                         = apply(url)
+  
+  /** Implicitly convert a [[scala.xml.Elem]] into a [[scala.sys.process.ProcessBuilder]] */
   implicit def xmlToProcess(command: scala.xml.Elem): ProcessBuilder      = apply(command)
+  
+  /** Implicitly convert a `String` into a [[scala.sys.process.ProcessBuilder]] */
   implicit def stringToProcess(command: String): ProcessBuilder           = apply(command)
+  
+  /** Implicitly convert a sequence of `String` into a [[scala.sys.process.ProcessBuilder]] */
   implicit def stringSeqToProcess(command: Seq[String]): ProcessBuilder   = apply(command)
 }

src/library/scala/sys/process/ProcessBuilder.scala

@@ -12,7 +12,66 @@ package process
 import processInternal._
 import ProcessBuilder._
 
-/** Represents a runnable process. */
+/** Represents a runnable process.
+  *
+  * This is the main component of this package. A `ProcessBuilder` may be composed with
+  * others, either concatenating their outputs or piping them from one to the next, and
+  * possibly with conditional execution depending on the last process exit value.
+  *
+  * Once executed, one can retrieve the output or redirect it to a 
+  * [[scala.sys.process.ProcessLogger]], or one can get the exit value, discarding or
+  * redirecting the output.
+  *
+  * 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]].
+  *
+  * 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 is different than zero. It mirrors shell's `&&`.
+  *
+  * Not shown here, the equivalent of a shell's `;` would be `###`. The reason for this name is
+  * that `;` is a reserved token in Scala.
+  *
+  * Finally, `!` at the end executes the commands, and returns the exit value. If the output
+  * was desired instead, one could run that with `!!` instead.
+  *
+  * If one wishes to execute the commands in background, one can either call `run`, which
+  * returns a [[scala.sys.process.Process]] from which the exit value can be obtained, or
+  * `lines`, which returns a [scala.collection.immutable.Stream] of output lines. This throws 
+  * an exception at the end of the `Stream` is the exit value is non-zero. To avoid exceptions,
+  * one can use `lines_!` instead.
+  *
+  * One can also start the commands in specific ways to further control their I/O. Using `!<` to
+  * start the commands will use the stdin from the current process for them. All methods can
+  * be used passing a [[scala.sys.process.ProcessLogger]] to capture the output, both stderr and
+  * stdout. And, when using `run`, one can pass a [[scala.sys.process.ProcessIO]] to control
+  * stdin, stdout and stderr.
+  *
+  * The stdin of a command can be redirected from a `java.io.InputStream`, a `java.io.File`, a
+  * `java.net.URL` or another `ProcessBuilder` through the method `#<`. Likewise, the stdout
+  * can be sent to a `java.io.OutputStream`, a `java.io.File` or another `ProcessBuilder` with
+  * the method `#>`. The method `#>>` can be used to append the output to a `java.io.File`.
+  * For example:
+  * 
+  * {{{
+  * new URL("http://databinder.net/dispatch/About") #> "grep JSON" #>> new File("About_JSON") !
+  * }}}
+  */
 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.*/
@@ -83,40 +142,75 @@ trait ProcessBuilder extends Source with Sink {
   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. */
+      * 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, "<output stream>"))
+    
+    /** Writes the output stream of this process to a [[scala.sys.process.ProcessBuilder]]. */
     def #>(b: ProcessBuilder): ProcessBuilder = new PipedBuilder(toSource, b, false)
+    
+    /** Returnes a [[scala.sys.process.ProcessBuilder]] representing this `Source`. */
     def cat = toSource
     private def toFile(f: File, append: Boolean) = #> (new FileOutput(f, append))
   }
+
+  /** Represents everything that can receive an output from a
+    * [[scala.sys.process.ProcessBuilder]].
+    */
   trait Sink {
     protected def toSink: ProcessBuilder
+    
     /** Reads the given file into the input stream of this process. */
     def #< (f: File): ProcessBuilder = #< (new FileInput(f))
+    
     /** Reads the given URL into the input stream of this process. */
     def #< (f: URL): ProcessBuilder = #< (new URLInput(f))
+    
     /** 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. */
+      * argument is call-by-name, so the stream is recreated, read, and closed each
+      * time this process is executed. 
+      */
     def #<(in: => InputStream): ProcessBuilder = #< (new IStreamBuilder(in, "<input stream>"))
+    
+    /** Reads the output of a [[scala.sys.process.ProcessBuilder]] into the input stream of this process. */
     def #<(b: ProcessBuilder): ProcessBuilder = new PipedBuilder(b, toSink, false)
   }
 }

src/library/scala/sys/process/ProcessIO.scala

@@ -11,7 +11,12 @@ package process
 
 import processInternal._
 
-/** Each method will be called in a separate thread.
+/** This class is used to control the I/O of every [[scala.sys.process.ProcessBuilder]].
+ *  Most of the time, there is no need to interact with `ProcessIO` directly. However, if
+ *  fine control over the I/O of a `ProcessBuilder` is desired, one can use the factories
+ *  on [[scala.sys.process.BasicIO]] stand-alone object to create one. 
+ *
+ *  Each method will be called in a separate thread.
  *  If daemonizeThreads is true, they will all be marked daemon threads.
  */
 final class ProcessIO(

src/library/scala/sys/process/ProcessLogger.scala

@@ -39,6 +39,7 @@ trait ProcessLogger {
   def buffer[T](f: => T): T
 }
 
+/** A [[scala.sys.process.ProcessLogger]] that writes output to a file. */
 class FileProcessLogger(file: File) extends ProcessLogger with Closeable with Flushable {
   private val writer = (
     new PrintWriter(
@@ -56,9 +57,26 @@ class FileProcessLogger(file: File) extends ProcessLogger with Closeable with Fl
   def flush(): Unit = writer.flush()
 }
 
+/** Provides factories to create [[scala.sys.process.ProcessLogger]], which
+ *  are used to capture output of [[scala.sys.process.ProcessBuilder]] commands
+ *  when run.
+ */
 object ProcessLogger {
+  /** Creates a [[scala.sys.process.ProcessLogger]] that redirects output to a `java.io.File`. */
   def apply(file: File): FileProcessLogger = new FileProcessLogger(file)
+  
+  /** Creates a [[scala.sys.process.ProcessLogger]] that sends all output, standard and error,
+   *  to the passed function.
+   */
   def apply(fn: String => Unit): ProcessLogger = apply(fn, fn)
+  
+  /** Creates a [[scala.sys.process.ProcessLogger]] that sends all output to the corresponding
+   *  function.
+   *
+   *  @param fout  This function will receive standard outpout.
+   *
+   *  @param ferr  This function will receive standard error.
+   */
   def apply(fout: String => Unit, ferr: String => Unit): ProcessLogger =
     new ProcessLogger {
       def out(s: => String): Unit = fout(s)

src/library/scala/sys/process/package.scala

@@ -11,6 +11,58 @@
 // for process debugging output.
 //
 package scala.sys {
+  /**
+    * This package is used to create process pipelines, similar to Unix command pipelines.
+    *
+    * The key concept is that one builds a [[scala.sys.process.Process]] that will run and return an exit
+    * value.  This `Process` is usually composed of one or more [[scala.sys.process.ProcessBuilder]], fed by a
+    * [[scala.sys.process.ProcessBuilder.Source]] and feeding a [[scala.sys.process.ProcessBuilder.Sink]]. A
+    * `ProcessBuilder` itself is both a `Source` and a `Sink`.
+    *
+    * As `ProcessBuilder`, `Sink` and `Source` are abstract, one usually creates them with `apply` methods on
+    * the companion object of [[scala.sys.process.Process]], or through implicit conversions available in this
+    * package object from `String` and other types. The pipe is composed through unix-like pipeline and I/O
+    * redirection operators available on [[scala.sys.process.ProcessBuilder]].
+    *
+    * The example below shows how to build and combine such commands. It searches for `null` uses in the `src`
+    * directory, printing a message indicating whether they were found or not. The first command pipes its
+    * output to the second command, whose exit value is then used to choose between the third or fourth
+    * commands. This same example is explained in greater detail on [[scala.sys.process.ProcessBuilder]].
+    *
+    * {{{
+    * import scala.sys.process._
+    * (
+    *     "find src -name *.scala -exec grep null {} ;"  
+    *     #|  "xargs test -z"  
+    *     #&&  "echo null-free"  #||  "echo null detected"
+    * ) !
+    * }}}
+    *
+    * Other implicits available here are for [[scala.sys.process.ProcessBuilder.FileBuilder]], which extends
+    * both `Sink` and `Source`, and for [[scala.sys.process.ProcessBuilder.URLBuilder]], which extends
+    * `Source` alone.
+    *
+    * One can even create a `Process` solely out of these, without running any command. For example, this will
+    * download from a URL to a file:
+    *
+    * {{{
+    * import java.io.File
+    * import scala.sys.process._
+    * new File("About.html") #> new File("About_copy.html") !
+    * }}}
+    *
+    * One may use a `Process` directly through `ProcessBuilder`'s `run` method, which starts the process in
+    * the background, and returns a `Process`. If background execution is not desired, one can get a
+    * `ProcessBuilder` to execute through a method such as `!`, `lines`, `run` or variations thereof. That
+    * will create the `Process` to execute the commands, and return either the exit value or the output, maybe
+    * throwing an exception.
+    *
+    * Finally, when executing a `ProcessBuilder`, one may pass a [[scala.sys.process.ProcessLogger]] to
+    * capture stdout and stderr of the executing processes. A `ProcessLogger` may be created through its
+    * companion object from functions of type `(String) => Unit`, or one might redirect it to a file, using
+    * [[scala.sys.process.FileProcessLogger]], which can also be created through `ProcessLogger`'s object
+    * companion.
+    */
   package object process extends ProcessImplicits {
     def javaVmArguments: List[String] = {
       import collection.JavaConversions._