Minimal python ctypes based example of logging to GENIVI Diagnostic Log and Trace Daemon

dlt-log-app.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Minimal example of writing logs to a dlt-daemon from a python app. The
# message will look like this when printed out using
# "dlt-receive -a localhost":
# 2016/03/10 10:24:42.772153  290716359 016 ECU1 DLTD INTM log info V 1 [ApplicationID 'APPY' registered for PID 29, Description=APPY service]
# 2016/03/10 10:24:42.772178  290716360 017 ECU1 DLTD INTM log info V 1 [ContextID 'APPY' registered for ApplicationID 'APPY', Description=Context for APPY]
# 2016/03/10 10:24:42.772182  290716359 000 ECU1 APPY APPY log info V 1 [This is a log message]
# 2016/03/10 10:24:42.772185  290716360 018 ECU1 DLTD INTM log info V 1 [Unregistered ContextID 'APPY' for ApplicationID 'APPY']
# 2016/03/10 10:24:42.772190  290716360 019 ECU1 DLTD INTM log info V 1 [Unregistered ApplicationID 'APPY']

import sys
from ctypes import *

class DltContext(Structure):
    _fields_ = [ ('contextID', c_char * 4),
                 ('log_level_pos', c_int32),
                 ('log_level_ptr', POINTER(c_int8)),
                 ('trace_status_ptr', POINTER(c_int8)),
                 ('mcnt', c_uint8)
                ]

def main(message):
    LOG_LEVEL_INFO = 0x04
    dlt = cdll.LoadLibrary('libdlt.so.2')
    dlt.dlt_register_app('APPY', 'APPY service')                            # DLT_REGISTER_APP(..)
    appy_ctx = DltContext()                                                 # DLT_DECLARE_CONTEXT(mein_ctx)
    dlt.dlt_register_context(byref(appy_ctx), 'APPY', 'Context for APPY')   # DLT_REGISTER_CONTEXT(..)
    dlt.dlt_log_string(byref(appy_ctx), LOG_LEVEL_INFO, message)
    dlt.dlt_unregister_context(byref(appy_ctx))
    dlt.dlt_unregister_app()

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print("Usage: ./%s <log message>" % sys.argv[0])
    else:
        main(' '.join(sys.argv[1:]))