Safety bag for your stdin.
This tool is handy when your stdout has pauses but you don't want to block stdin.
To archieve this bag reads stdin, saves it in ring buffer and output to stdout from ring buffer.
In case of stdout block input will be saved in ring buffer until it fills up.
In the latter case it will block stdin.
The size of the bag (the ringbuffer) is set by lines of size 16 * LINE_MAX that usually is 16 * 2048 = 32K lines.
To manage stdin, stdout and signals it will poll it with poll (signal is polled with signalfd).