Log printing of each layer of Android

application

import android.util.Log;
Log.v();
Log.d();
Log.i();
Log.w();
Log.e();
Log.wtf();
Log.wtfStack();

framework java

import android.util.Slog;
Slog.v();
Slog.d();
Slog.i();
Slog.w();
Slog.e();
Slog.wtf();
Slog.wtfQuiet();
Slog.wtfStack();

framework native

c language style

#include <cutils/log.h>
LOG_ALWAYS_FATAL_IF(...);
LOG_ALWAYS_FATAL(...);
LOG_FATAL_IF(...);
LOG_FATAL(...);
ALOG_ASSERT(...);
ALOGV(...);
ALOGV_IF(...);
ALOGD(...);
ALOGD_IF(...);
ALOGI(...);
ALOGI_IF(...);
ALOGW(...);
ALOGW_IF(...);
ALOGE(...);
ALOGE_IF(...);

c++ style

#include <android-base/logging.h>

LOG(VERBOSE) << "We didn't expect to reach here";
LOG(DEBUG) << "We didn't expect to reach here";
LOG(INFO) << "We didn't expect to reach here";
LOG(WARNING) << "We didn't expect to reach here";
LOG(ERROR) << "We didn't expect to reach here";
LOG(FATAL_WITHOUT_ABORT) << "We didn't expect to reach here";
LOG(FATAL) << "We didn't expect to reach here";

native stack print

1、进入对应的cpp文件，放开#define LOG_NDEBUG 0注释，且变成#define LOG_NDEBUG 1

2、声明头文件
#include<utils/CallStack.h>
#include<utils/Log.h>

3、调用方法：
android::CallStack stack;
stack.update();
stack.log(debug); //输出到logcat

4、mk或者bp中需要链接以下so库：
libutils
libcutils

HAL

#include <utils/Log.h>
LOG_ALWAYS_FATAL_IF(...);
LOG_ALWAYS_FATAL(...);
LOG_FATAL_IF(...);
LOG_FATAL(...);
ALOG_ASSERT(...);
ALOGV(...);
ALOGV_IF(...);
ALOGD(...);
ALOGD_IF(...);
ALOGI(...);
ALOGI_IF(...);
ALOGW(...);
ALOGW_IF(...);
ALOGE(...);
ALOGE_IF(...);

Kernel

Through cat /proc/sys/kernel/printkthis file, view the default log level of the system

xxxxx:/ # cat /proc/sys/kernel/printk
7       4       1       7

From left to right:

• 7It represents console_loglevel: the log level of the console, and printkthe output information will be printed to the console with a higher priority than it

• 4Represents default_message_loglevel: the default message log level, if printkno priority is specified, the default priority is it

• 1Represents minimum_console_loglevel: the lowest console log level, the minimum value that the console log level can be set

• 7Represents default_console_loglevel: the default console log level, the default value of the console log level

The level can be changed console_loglevelto allow more kernel logs to be printed

xxxxx:/ # echo 0 > /proc/sys/kernel/printk

printk(KERN_EMERG   "KERN_EMERG\n");
printk(KERN_ALERT   "KERN_ALERT\n");
printk(KERN_CRIT    "KERN_CRIT\n");
printk(KERN_ERR     "KERN_ERR\n");
printk(KERN_WARNING "KERN_WARNING\n");
printk(KERN_NOTICE  "KERN_NOTICE\n");
printk(KERN_INFO    "KERN_INFO\n");
printk(KERN_DEBUG   "KERN_DEBUG\n");