Android Logging System - Revision history

Tim Bird: /* Capturing stdout */ add section about 'log' command line tool

2012-02-07T19:54:12Z

‎Capturing stdout: add section about 'log' command line tool

Wmat: Added page to Category:Android

2011-02-22T20:11:12Z

Added page to Category:Android

Tim Bird: /* Logcat command */ add trick about joining android log and kernel log

2011-01-20T19:51:56Z

‎Logcat command: add trick about joining android log and kernel log

Tim Bird: /* Capturing stdout */ add source reference

2011-01-20T19:38:26Z

‎Capturing stdout: add source reference

Tim Bird: /* Capturing stdout */ add logwrapper usage

2011-01-20T19:37:55Z

‎Capturing stdout: add logwrapper usage

Tim Bird: /* logwrapper */

2011-01-15T01:22:25Z

‎logwrapper

Tim Bird at 01:21, 15 January 2011

2011-01-15T01:21:13Z

Tim Bird at 01:16, 15 January 2011

2011-01-15T01:16:38Z

Tim Bird: adjust image

2011-01-15T01:15:17Z

adjust image

Tim Bird at 01:07, 15 January 2011

2011-01-15T01:07:40Z

@@ Line 53: / Line 53: @@
 In all cases, eventually a formatted message is delivered through the C/C++ library down to the kernel driver, which stores the message in the appropriate buffer.
-== Capturing stdout ==
+== 'log' command line tool ==
 It is sometimes useful to capture stdout from native applications into the log.  There is a utility called
 'logwrapper' which can be used to run a program, and redirect it's stdout into log messages.

← Older revision		Revision as of 20:11, 22 February 2011
Line 102:		Line 102:
	* [http://developer.android.com/guide/developing/tools/adb.html Android Debug Bridge reference page] - has 'adb logcat' usage information		* [http://developer.android.com/guide/developing/tools/adb.html Android Debug Bridge reference page] - has 'adb logcat' usage information
	* [http://blog.kmckk.com/archives/2936958.html Logging System Of Android] Presentation by Tetsuyuki Kobayashi, September, 2010 at CELF's [[Japan Technical Jamboree 34]]		* [http://blog.kmckk.com/archives/2936958.html Logging System Of Android] Presentation by Tetsuyuki Kobayashi, September, 2010 at CELF's [[Japan Technical Jamboree 34]]
		+
		+	[[Category:Android]]

@@ Line 80: / Line 80: @@
 ** You can filter the messages by tag and log level, with a different level per tag.
 * You can specify (using a system property) that various programs emit their stdout or stderr to the log.
 == Resources ==
 * [http://developer.android.com/guide/developing/tools/adb.html Android Debug Bridge reference page] - has 'adb logcat' usage information
 * [http://blog.kmckk.com/archives/2936958.html Logging System Of Android] Presentation by Tetsuyuki Kobayashi, September, 2010 at CELF's [[Japan Technical Jamboree 34]]

@@ Line 66: / Line 66: @@
   -x: Causes logwrapper to SIGSEGV when BINARY terminates
       fault address is set to the status of wait()
 == Logcat command ==

@@ Line 56: / Line 56: @@
 It is sometimes useful to capture stdout from native applications into the log.  There is a utility called
 'logwrapper' which can be used to run a program, and redirect it's stdout into log messages.
 == Logcat command ==

@@ Line 27: / Line 27: @@
 Each message in the log consists of a tag indicating the part of the system or application that the message came from,
-a timestamp, the message log level (or severity of the event represented by the message) and the log message itself.
+a timestamp, the message log level (or ''priority'' of the event represented by the message) and the log message itself.
 All of the log buffers except for 'event' use free-form text messages.  The 'event' buffer is a 'binary' buffer,
@@ Line 41: / Line 41: @@
 == System and Application logging ==
 === Application log ===
-An Android application includes the [http://developer.android.com/reference/android/util/Log.html android.util.Log class], and uses methods of this class to write messages
+An Android application includes the [http://developer.android.com/reference/android/util/Log.html android.util.Log class], and uses methods of this class to write messages of different priority into the log.
-of different severity into the log.
-Java classes declare their tag statically as a string, which they pass to the log method.  The log method used indicates the message "severity" (or log level).  Messages can be filtered by tag or log level when the logs are processed by retrieval tools (logcat).
+Java classes declare their tag statically as a string, which they pass to the log method.  The log method used indicates the message "severity" (or log level).  Messages can be filtered by tag or priority when the logs are processed by retrieval tools (logcat).
 === Event log ===
@@ Line 66: / Line 65: @@
 Some quick notes:
-* Log messages each have a tag and log level.
+* Log messages each have a tag and priority.
 ** You can filter the messages by tag and log level, with a different level per tag.
 * You can specify (using a system property) that various programs emit their stdout or stderr to the log.

@@ Line 5: / Line 5: @@
 This is separate from the Linux kernel's own logging system, which is accessed using 'dmesg' or '/proc/kmsg'.  However, the logging system does store messages in kernel buffers.
-[[image:Android-logging-kmc-kobayashi.png|right|image by Tetsuyuki Kobabayshi, of Kyoto MicroComputers]]
+[[image:Android-logging-kmc-kobayashi.png|right|frame|image by Tetsuyuki Kobabayshi, of Kyoto Microcomputer Co.]]
 The logging system consists of:

@@ Line 1: / Line 1: @@
 This article describes the Android logging system
 == Overview ==
 The Android system has a logging facility that allows systemwide logging of information, from applications and system components.
 This is separate from the Linux kernel's own logging system, which is accessed using 'dmesg' or '/proc/kmsg'.  However, the logging system does store messages in kernel buffers.
 The logging system consists of:
@@ Line 22: / Line 25: @@
 buffer (outside of '/dev/log/main') so that a single verbose application couldn't overrun system messages
 and cause them to be lost.
 Each message in the log consists of a tag indicating the part of the system or application that the message came from,

@@ Line 24: / Line 24: @@
 [[image:Android-logging-kmc-kobayashi.png]]
 == Kernel driver ==
 The kernel driver for logging is called the 'logger'. See [[Android logger]]
 == Logcat command ==