I've written a domain (unix) socket server. The server logs to stderr. I also wrote a simple application which reads from stdin and generates rolling log files. Currently I had it working fine doing something like the following:

./aggregator <some args> 2>&1 >/dev/null | ./logrot --daily ~/logs/agglog

aggregator is my daemon and logrot is the rolling log file tool.

I have been looking into writing a daemon script for my daemon and also found the following link:

http://www.faqs.org/faqs/unix-faq/programmer/faq/

where 1.7 talks about how daemons should work. So I added the fork()/setsid()/fork()/chdir()/umask(). All seems to work fine but now the command above which used to work no longer works, or at least doesn't seem to work as I expect it to. When I execute it the shell is blocked for some reason. I assume it's the pipe that's causing the problem but not sure exactly why. Also, I'm wondering whether I need to put the rolling log file logic inside my daemon in order for it to work. Any ideas?

Thanks,
Nick

How'd you accomplish fork() from within a script?

In my world a daemon is created following the same process described in that link and you'll also find a blog entry in my list of blogs pretty much mirroring that same procedure, but using C code.

My most important point here though:
Since you've written aggregator, then why not just use open() and close() or fopen() and fclose() and write your own logs to files? No need to channel stdout and stderr in this manner, instead create logging from within your program.

I'm actually "funny", meaning "odd" in that I really don't use the syslog utilities from Linux. Probably because I've worked in non-OS or limited RTOS environments and had to create all support functions on my own for lack of having library functions available. As a result, I create my own logging utilities and macros. All they are, are the equivalent of printf(format-string, ...) allowing variable arguments, but instead of sending the logged data to stdout/stderr, they place my resultant log data into specific files. And given large architectures, we've usually segregated log files per major functional blocks. All related to the common libraries, go to one log file, all related to a particular sub-system, go to a log file for that sub-system.

My aggregator program is written in c. The part about the script was just that I had been working on writing a daemon script, eg. start stop etc., for my daemon and ran upon the link which talks about how a daemon should be written. So I added many of those points to my daemon and then found that the logging was no longer working.

I can certainly add the rolling log logic to my daemon, but it seemed useful to have a tool which would do that from any stdin and thus could work for many applications.

Thanks,
Nick

Yes, sorry. I did see "I have been looking into writing a daemon script ..." and interpreted that incorrectly.

Advice still stands though. No need to use stdout/err, instead write log files from within your code. Or use the syslog library. From what I've heard, it's good and I know it's very much used by standard Linux application programmers. Just I've never practiced that, which is my personal shortcoming.

1 members found this post helpful.

I do not know what did you really write, but in general a daemon will not write its stdout, but a logfile directly.
Also I do not really know what does it: "When I execute it the shell is blocked for some reason" really mean.
Did you try to use syslog and the "official" logrotate utility?

1 members found this post helpful.

By "the shell being blocked" I mean that it's waiting on something. Normally, with the forks I added, the shell should return back and give me another prompt. However, it's blocked on something when I add my logging stuff (eg. the pipe to logrot).

I'm somewhat new to Linux though I'm aware that syslog is a popular logging mechanism. I will look into that some more.

Thanks,
Nick

without showing us what did you really coded we will not be able to help you further....