From 8b9d9669bb7e3e3f3806a16ea5b7440804356e40 Mon Sep 17 00:00:00 2001
From: Morten Hustveit <morten.hustveit@gmail.com>
Date: Thu, 10 Nov 2016 15:39:52 -0500
Subject: [PATCH] Have ConsoleLogger log to stderr instead of stdout (#1714)

On Unix systems, it's common for programs to read their input from stdin, and
write their output to stdout.  Messages should be written to stderr, where they
won't corrupt a program's output, and where they can be seen by the user even
if the output is being redirected.

This is mostly a problem when XGBoost is being used from Python or from another
program.
---
 src/logging.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/logging.cc b/src/logging.cc
index f579f9a97..934bb0414 100644
--- a/src/logging.cc
+++ b/src/logging.cc
@@ -12,7 +12,7 @@ namespace xgboost {
 
 #if XGBOOST_CUSTOMIZE_LOGGER == 0
 ConsoleLogger::~ConsoleLogger() {
-  std::cout << log_stream_.str() << std::endl;
+  std::cerr << log_stream_.str() << std::endl;
 }
 
 TrackerLogger::~TrackerLogger() {