Answers to: Programming logic question

Answer by darkonc

darkonc — Wed, 06 Mar 2013 01:16:18 -0500

One thing to be aware of is that -- if you're using fgets, you should call setlinebuf to set line-buffering so that you don't get stuck waiting for time-critical data to clear the buffers.

Answer by DBA

DBA — Tue, 27 Jul 2010 01:47:12 -0400

You might also find the command "tee" useful. It not only splits an output stream, but can write to any named pipe rather than just to a file. That would make real-time monitoring easier since you can parse the pipe by character if you wish.

See man(1) tee or http://en.wikipedia.org/wiki/Tee_%28command%29

Good Luck.

Answer by Web31337

Web31337 — Fri, 11 Jun 2010 12:38:31 -0400

there's "inotail" util can be used instead of "tail" if your kernel has inotify enabled(most default kernels from modern distros do). you can use it with the way Sander Marechal shown, or you can code your own app using inotify functions on C or other lang providing inotify API(say, python).

Answer by Sander Marechal

Sander Marechal — Thu, 10 Jun 2010 22:28:49 -0400

Make a filter and use tail. You could use the filter like so:

$ tail -f some.log | monitor

Where monitor is your filter. In the monitor app, simply use fgets() to read from STDIN. fgets() reads from a handle and returns a complete line (ending in a new line). If there's no full ine yet, it simply waits. So, you call fgets(), wait for a line, act on it, then jump back to gfets() again.

This follows the UNIX philosophy. Do one thing and do it well. Use tail to follow the file. Use your monitor just to act on the lines.