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rtmex 04-25-2007 04:45 PM

How to redirect to a file the output of a service?
 
Hi, I had this server program that opens a socket and listen to messages that another program sends to it.

When The server program starts send this to the console
printf("%s: Listening to service port = %d\n", srv->s_name, ntohs(srv->s_port));

And also puts out the messages that he gets from the other program (the client)

I need to run the server program as a service when the user enters the runlevel 3 (I already made the corresponding script in /etc/init.d and the symlinks in the /etc/rc3.d directory, etc. etc.)

The problem I can't solve is that I need to redirect the server program messages to a file instead of the console, WITHOUT modifying the source code of the program. Let say the exe file and the shell script are called prueba.

I try ./prueba > /tmp/serv.log

Then I press Ctrl-C to finish the program and when I look into the /tmp directory, there's the serv.log file but it does not have anything, even when the messages did not appear on screen.

What am i doing wrong?

Thanks in advance

rtmex

wjevans_7d1@yahoo.co 04-25-2007 07:24 PM

Do you mean that you can't change the source of the file when switching between outputting to the console and outputting to a file?

Or do you mean that it's forbidden to change the file under any circumstances?

If it's the second of these, I can't help you.

If it's the first, then place this just after each printf() call:

Code:

fflush(stdout);
That won't hurt anything when outputting to the console, and might help when outputting to the file.

Another thing to try: Run a "Hello, world!" program under the same situation, and see whether it outputs to the temp file. If it doesn't, we all have a serious problem. (grin) If it does, make a temporary version of your program and make it more and more like the "Hello, world!" program until it output something.

Hope this helps.

rtmex 04-25-2007 08:04 PM

:) Kind of a test
 
I have found a similar solution (implies modifying the source code)

setlinebuf(stdout);

But that's not what I must do (that's the test)

I think it must be something like configuring the inetd.conf file, but I'm not sure what changes should I must do, I'm trying calling netcat in the inetd.conf file, but unsuccesfully so far.

Thanks, so, I'm still open to ideas :)

rtmex 04-26-2007 10:22 PM

I found that what I need to do is to modify the syslog.conf file, I put this line on that file

prueba.* -/tmp/serv.log

The idea is that all messages generated by the service prueba goes to the serv.log file located in the /tmp directory, but is does not work.

Does anyone know why?

Thanks

wjevans_7d1@yahoo.co 04-26-2007 11:51 PM

But ... but ...

You still have a problem that has nothing to do with any configuration files, right?

Quote:

I try ./prueba > /tmp/serv.log

Then I press Ctrl-C to finish the program and when I look into the /tmp directory, there's the serv.log file but it does not have anything, even when the messages did not appear on screen.
Is this still a problem?

rtmex 04-27-2007 12:09 AM

The problem is still the same "How to redirect to a file the output of a service?" (but as I explained in my second post WITHOUT changing the source code of the program.

I think ./prueba > /tmp/serv.log will not work unless I change the source code (using what you suggested or what I found) but that does not solve my problem because I need to do it WITHOUT changing the source code :)

I found I can do that (redirect the output of the service to a file whithout toucing the source code of the program) using the syslogd.conf file, but I don't know exactly how.

I already changed the syslogd.conf adding

prueba.* -/tmp/serv.log

But when I restart the system (cuz syslogd restart did not work) I got a message saying that the Facility prueba does not exist.

I know maybe this is something very easy to do, but I'm new at linux that's why I post on this forum (newbie)

:)


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