From a1133b215a7a84968113381ab9d49a4a464f1081 Mon Sep 17 00:00:00 2001
From: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Date: Tue, 27 Aug 2013 21:16:22 +0200
Subject: add QProcess::nullDevice()

Change-Id: I15273fa3f3ba323a835350153f2a20404f12420b
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/io/qprocess.cpp | 27 +++++++++++++++++++++++++++
 src/corelib/io/qprocess.h   |  2 ++
 2 files changed, 29 insertions(+)

(limited to 'src/corelib')

diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp
index 96cec568df..d473281acc 100644
--- a/src/corelib/io/qprocess.cpp
+++ b/src/corelib/io/qprocess.cpp
@@ -1317,6 +1317,10 @@ void QProcess::closeWriteChannel()
     object will be in read-only mode (calling write() will result in
     error).
 
+    To make the process read EOF right away, pass nullDevice() here.
+    This is cleaner than using closeWriteChannel() before writing any
+    data, because it can be set up prior to starting the process.
+
     If the file \a fileName does not exist at the moment start() is
     called or is not readable, starting the process will fail.
 
@@ -1340,6 +1344,10 @@ void QProcess::setStandardInputFile(const QString &fileName)
     read channel is closed: reading from it using read() will always
     fail, as will readAllStandardOutput().
 
+    To discard all standard output from the process, pass nullDevice()
+    here. This is more efficient than simply never reading the standard
+    output, as no QProcess buffers are filled.
+
     If the file \a fileName doesn't exist at the moment start() is
     called, it will be created. If it cannot be created, the starting
     will fail.
@@ -2439,6 +2447,25 @@ QStringList QProcess::systemEnvironment()
     \sa QProcess::systemEnvironment()
 */
 
+/*!
+    \since 5.2
+
+    \brief The null device of the operating system.
+
+    The returned file path uses native directory separators.
+
+    \sa QProcess::setStandardInputFile(), QProcess::setStandardOutputFile(),
+        QProcess::setStandardErrorFile()
+*/
+QString QProcess::nullDevice()
+{
+#ifdef Q_OS_WIN
+    return QStringLiteral("\\\\.\\NUL");
+#else
+    return QStringLiteral("/dev/null");
+#endif
+}
+
 /*!
     \typedef Q_PID
     \relates QProcess
diff --git a/src/corelib/io/qprocess.h b/src/corelib/io/qprocess.h
index 9da3e63f38..2919788e34 100644
--- a/src/corelib/io/qprocess.h
+++ b/src/corelib/io/qprocess.h
@@ -209,6 +209,8 @@ public:
 
     static QStringList systemEnvironment();
 
+    static QString nullDevice();
+
 public Q_SLOTS:
     void terminate();
     void kill();
-- 
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