[uClibc]Trying to output <stdout,stderr> messages in the serial console

George Thanos gthanos at telecom.ntua.gr
Fri Mar 14 15:07:54 UTC 2003

Markus Pietrek wrote:

>Hi George,
>>The next big step is print some messages in the serial console. I assume
>>that when we fprintf in stdout or stderr, our messages should be
>>redirected to the systems console. Am I write on this? When executing a
>>regular application in /bin/sh this application should be able to output
>>formatted messages to the serial port?
>How do you launch your application? Do you replace init by your application or 
>modify init to call your application?
Actually I was using my applcation in place of init which I suppose is 
wrong. I will compile init from the userland.old repo of uClinux and try 
to execute it instead.

>The application inherits stdout, stderr and stdin from its parent. And I think 
>init must open /dev/ttyS0 or /dev/tty itself first.
>And /dev/console provides only output, so it may be ok for stdout and stderr. 
>It also uses many kernel buffers for retreiving the messages later (like 
>dmesg does). It is also important that /dev/console is used by other kernel 
>functions, so your text may be overwritten.
I understand. I also made some tests trying to open /dev/ttyS0. I open 
it and tried to output something there. It works fine and outputs the 
messages in the serial port.  Thus /dev/ttyS0 works OK.

Thanks for your help,

- George


"Luck is what happens when preparation meets opportunity"

More information about the uClibc mailing list