Mobile native Wearable native

dlog: Sending Log Output for Debug Activities

This tutorial demonstrates how you can send log messages to a circular log device and check them.

Warm-up

Become familiar with the dlog API basics by learning about:

Initializing dlog

To initialize dlog:

  1. To use the functions and data types of the dlog API (in mobile and wearable applications), include the <dlog.h> header file in your application:

    #include <dlog.h>
  2. Make sure you have the necessary tools:
    • dlog library: libdlog.so

      The dlog library provides a logging function to send log messages to the kernel log device.

    • dlogutil: dlogutil

      dlogutil enables you to view log messages in the log device, and provides filtered message output.

    • Requirement: linux-2.6.32 kernel

Sending a Log Message

Send a log message with the MY_APP tag with various priorities.

#include<dlog.h>
#define TAG "MY_APP"

int main(void)
{
   int integer = 21;
   char string[] = "test dlog";

   dlog_print(DLOG_DEBUG, TAG, "debug message");
   dlog_print(DLOG_INFO, TAG, "info message");
   dlog_print(DLOG_WARN, TAG, "warning message");
   dlog_print(DLOG_ERROR, TAG, "error message");
   dlog_print(DLOG_INFO, TAG, "%s, %d", string, integer);

   return 0;
}

Checking the Output Logs

Execute dlogutil on the device sdb shell to check the out log.

Check the sdb guide to connect to a target and use it.

Desktop:~$ sdb shell
sh-3.2#
sh-3.2# dlogutil MY_APP
arc = 2, optind = 1, Kb 0, rotate 4
--------- beginning of /dev/log_system
--------- beginning of /dev/log_main
D/MY_APP  (11097): debug message
I/MY_APP  (11097): info message
W/MY_APP  (11097): warning message
E/MY_APP  (11097): error message
I/MY_APP  (11097): test dlog, 21
sh-3.2# dlogutil MY_APP:I
arc = 2, optind = 1, Kb 0, rotate 4
--------- beginning of /dev/log_system
--------- beginning of /dev/log_main
I/MY_APP  (11097): info message
W/MY_APP  (11097): warning message
E/MY_APP  (11097): error message
I/MY_APP  (11097): test dlog, 21
sh-3.2# dlogutil MY_APP:W
arc = 2, optind = 1, Kb 0, rotate 4
--------- beginning of /dev/log_system
--------- beginning of /dev/log_main
W/MY_APP  (11097): warning message
E/MY_APP  (11097): error message
sh-3.2# dlogutil MY_APP:E
arc = 2, optind = 1, Kb 0, rotate 4
--------- beginning of /dev/log_system
--------- beginning of /dev/log_main
E/MY_APP  (11097): error message
sh-3.2# dlogutil -v time MY_APP  
arc = 4, optind = 3, Kb 0, rotate 4
--------- beginning of /dev/log_system
--------- beginning of /dev/log_main
12-26 07:06:02.084+0000 D/MY_APP  (11097): debug message
12-26 07:06:02.084+0000 I/MY_APP  (11097): info message
12-26 07:06:02.084+0000 W/MY_APP  (11097): warning message
12-26 07:06:02.084+0000 E/MY_APP  (11097): error message
12-26 07:06:02.084+0000 I/MY_APP  (11097): test dlog, 21
sh-3.2# dlogutil -v threadtime MY_APP
arc = 4, optind = 3, Kb 0, rotate 4
--------- beginning of /dev/log_system
--------- beginning of /dev/log_main
12-26 07:06:02.084+0000 11097 11097 D MY_APP  : debug message
12-26 07:06:02.084+0000 11097 11097 I MY_APP  : info message
12-26 07:06:02.084+0000 11097 11097 W MY_APP  : warning message
12-26 07:06:02.084+0000 11097 11097 E MY_APP  : error message
12-26 07:06:02.084+0000 11097 11097 I MY_APP  : test dlog, 21
sh-3.2# dlogutil -v long MY_APP
arc = 4, optind = 3, Kb 0, rotate 4
--------- beginning of /dev/log_system
--------- beginning of /dev/log_main
[ 12-26 07:06:02.084 11097:11097 D/MY_APP   ]
debug message

[ 12-26 07:06:02.084 11097:11097 I/MY_APP   ]
info message

[ 12-26 07:06:02.084 11097:11097 W/MY_APP   ]
warning message

[ 12-26 07:06:02.084 11097:11097 E/MY_APP   ]
error message

[ 12-26 07:06:02.084 11097:11097 I/MY_APP   ]
test dlog, 21
sh-3.2# dlogutil -v raw MY_APP
arc = 4, optind = 3, Kb 0, rotate 4
--------- beginning of /dev/log_system
--------- beginning of /dev/log_main
debug message
info message
warning message
error message
test dlog, 21
sh-3.2# dlogutil -v brief MY_APP
arc = 4, optind = 3, Kb 0, rotate 4
--------- beginning of /dev/log_system
--------- beginning of /dev/log_main
D/MY_APP  (11097): debug message
I/MY_APP  (11097): info message
W/MY_APP  (11097): warning message
E/MY_APP  (11097): error message
I/MY_APP  (11097): test dlog, 21
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