Message formats

In addition to the pre-configured formats, custom formats can be created. In the spirit of this being a library, they are created outside the library source. See the formats.c example source file.

Pre-configured output formats available

• log_fmt_basic
• log_fmt_standard
• log_fmt_debug
• log_fmt_debug_tid
• log_fmt_debug_tname
• log_fmt_debug_tall
• log_fmt_elapsed_time Elapsed time from channel initialization. Starting time may be reset.
• log_fmt_xml Structured format.
• log_fmt_json Structured format.

log_fmt_basic

Output messages with just the user message.

eth0     AF_PACKET (17)

log_fmt_systemd

Output messages in systemd compatible format. Systemd log messages have their log level enclosed in angle brackets prepended to the user message. When viewed through journalctl, timestamps are added, so only the log level and user message are needed.

<7>eth0     AF_PACKET (17)

log_fmt_standard

Output messages with timestamp, level and message.

2020-05-25 16:55:18.821 DEBUG   eth0     AF_PACKET (17)

log_fmt_debug

Output messages with timestamp, level, source code file, function, and line number, and finally the message.

2020-05-25 17:28:17.011 DEBUG   test-logger.c:main:110 eth0     AF_PACKET (17)

log_fmt_debug_tid

log_fmt_debug with thread id added

2020-05-25 17:28:17.011 DEBUG   65623 test-logger.c:main:110 nth0     AF_PACKET (17)

log_fmt_debug_tname

log_fmt_debug with thread name added

2020-05-25 17:28:17.011 DEBUG   thread_2 test-logger.c:main:110 eth0     AF_PACKET (17)

log_fmt_debug_tall

log_fmt_debug with thread id and thread name added

2020-05-25 17:28:17.011 DEBUG   65623:thread_2 test-logger.c:main:110 eth0     AF_PACKET (17)

log_fmt_elapsed_time

log_fmt_debug with elapsed time timestamp

0.000001665 INFO    formats.c:main:172 this message has elapsed time
0.000010344 INFO    formats.c:main:173 this message has elapsed time
0.000018740 INFO    formats.c:main:174 this message has elapsed time

log_fmt_xml

Output messages in java.util.logging.XMLFormatter format.

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE log SYSTEM "logger.dtd">
<log>
<record>
  <date>2020-08-15T23:10:49.081-04:00</date>
  <millis>1597547449081</millis>
  <nanos>969853</nanos>
  <sequence>1</sequence>
  <logger>tinylogger</logger>
  <level>INFO</level>
  <class>xml.c</class>
  <method>main</method>
  <thread>389042</thread>
  <message>Special chars are escaped in the &quot;&lt;xml&gt;&quot; format. &amp; it&apos;s msg #0.</message>
</record>
<record>
  <date>2020-08-15T23:10:49.082-04:00</date>
  <millis>1597547449082</millis>
  <nanos>112552</nanos>
  <sequence>2</sequence>
  <logger>tinylogger</logger>
  <level>INFO</level>
  <class>xml.c</class>
  <method>main</method>
  <thread>389042</thread>
  <message>Special chars are escaped in the &quot;&lt;xml&gt;&quot; format. &amp; it&apos;s msg #1.</message>
</record>
</log>

log_fmt_json

Output message in json format.

{
  "records" : [  {
    "isoDateTime" : "2020-07-31T15:12:56.408789290-04:00",
    "timespec" : {
      "sec" : 1596222776,
      "nsec" : 408789290
    },
    "sequence" : 1,
    "logger" : "tinylogger",
    "level" : "INFO",
    "file" : "json-hello.c",
    "function" : "main",
    "line" : 32,
    "threadId" : 164933,
    "threadName" : "json-hello",
    "message" : "hello world (msg 0)"
  },  {
    "isoDateTime" : "2020-07-31T15:12:56.408893063-04:00",
    "timespec" : {
      "sec" : 1596222776,
      "nsec" : 408893063
    },
    "sequence" : 2,
    "logger" : "tinylogger",
    "level" : "INFO",
    "file" : "json-hello.c",
    "function" : "main",
    "line" : 32,
    "threadId" : 164933,
    "threadName" : "json-hello",
    "message" : "hello world (msg 1)"
  } ]
}