This function is a non-portable RTLinux extension.
The rtl_printf function converts and formats its arguments similarly to printf(3) and places output to the kernel message buffer. Unlike the Linux kernel printk output facility, rtl_printf is safe to use from RTLinux threads and interrupt handlers.
This function returns the number of bytes output on success, and a negative value on error.
Generally, if at the Linux console, the kernel messages that rtl_printf produces are visible on the screen. You can also use the dmesg(1) command to view the kernel messages buffer. This is particularly useful when working in X. In addition, the syslogd(8) daemon is often configured to place the kernel messages to /var/log/messages.
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