What is the similar to printk in user mode?

We can us开发者_运维问答e printk to send debug message in kernel driver. I have a user mode AP that call kernel driver. I would like to output user mode AP debug message with kernel mode driver at the same time. How to do that?

If I understood your question correctly, I guess you are looking for syslog C API. $ man 3 syslog tells you everything you need.

You might want to check out syslog(). Generally though, you can probably do what you want without playing in the system log by using the normal print function for whatever language you're using in userspace, and manually looking at the two different outputs.