C and Python Syslog samples.

Use Unix syslog APIs to log various levels of messages.

To build the executable syslogexample,

# Generate configure and Makefile.in.
$ aclocal
$ autoconf
$ automake --add-missing

# Build the program syslog_example.c.
$ ./configure
$ make

After running the executable, you should see the following output in console,

The old log mask is 0x000000ff and the new log mask is 0x0000000f
The old log mask is 0x0000000f and the new log mask is 0x0000007f

and the following messages in the syslog which in Ubuntu is the file /var/log/syslog.

Jul 18 18:52:09 renwei-ubuntu SmartConn-Syslog[21940]: This is an informational message.
Jul 18 18:52:09 renwei-ubuntu SmartConn-Syslog[21940]: This is an error message.
Jul 18 18:52:09 renwei-ubuntu SmartConn-Syslog[21940]: This is a warning message again.

1. For detailed info about syslog APIs openlog, syslog, and closelog, please refer to "man 3 syslog".

2. For detailed info about setlogmask, please refer to "man 3 setlogmask".

Use the syslog and logger+SysLogHandler modules to log various levels of messages.

After running syslogExample.py, you should see the following output in console,

The old priority mask is 0xff and the new priority mask is 0xf.

and the following messages in the syslog which in Ubuntu is the file /var/log/syslog.

Jul 18 20:05:12 renwei-ubuntu Program-Name[22188]: This is an informational message.
Jul 18 20:05:12 renwei-ubuntu Program-Name[22188]: This is an error message.

After running syslogHandlerExample.py, you should see the following messages in the syslog which in Ubuntu is the file /var/log/syslog.

Jul 18 20:05:42 renwei-ubuntu INFO Module-Name[22196]: This is a informational message.
Jul 18 20:05:42 renwei-ubuntu ERROR Module-Name[22196]: This is an error message.

1. syslog is more straight-forward to use than logger+SysLogHandler.

2. In general, logger+SysLogHandler modules are more powerful than syslog, since they can log the messages to a remote UNIX machine.

3. logger+SysLogHandler can customize the format of the logging messages but syslog can't.

$ tail -f /var/log/syslog

Here we assume that syslog is written into the log file /var/log/syslog.

Take Ubuntu 14.04 LTS as an example where tty12 is selected as the unused tty session.

1. Grant the access for /dev/tty12 to the syslog user.

   (1) Add the syslog user to the owner group tty of /dev/tty12.

   $ sudo gpasswd --add syslog tty

   (2) Grant the read and write access of /dev/tty12 to the group tty.

   $ sudo chmod g+rw /dev/tty12

   (3) Kill all processes owned by the syslog user.

   $ sudo pkill -KILL -u syslog

   (4) Verify that the syslog user has been added to the group tty.

   $ groups syslog

2. Configure the syslog service to write the logging messages with the facility "user" to /dev/tty12.

   $ sudo vi /etc/rsyslog.d/50-default.conf

   Add the following line at the bottom of the conf file.

   user.*	|/dev/tty12
   

   The above "user" can be replaced by another facility or "*" (to match all facilities).

   Then restart the syslog service to make effective the configuration change.

   $ sudo service rsyslog restart

   Note that the syslog service on Ubuntu is named as "rsyslog".

3. After running the C/Python exectuable, you can switch to the tty12 session either via "Ctrl + Alt + F12" or the command

$ sudo chvt 12

, and you should be able to view the syslog messages with the facility "user" there.

If somehow the tty12 session hangs, you can switch back to the X session (i.e., the normal desktop), find the tty12 process, and kill it.

$ sudo fuser /dev/tty12
$ sudo kill [process-ID]