[FFmpeg-user] Read constantly updating video file

[Daniil Herasymov]

Hello!
Sorry if it's been discussed already, but I am wondering if it's
possible to read from a file that is currently being updated.
So I am recording a video from camera to some temp file, and while its
being recording (and file is getting bigger) I want to read it and
send data to RTMP server via ffmpeg.
I tried to use simlple ffmpeg -re -i someTempFile.mov -c:v h264 -f flv
rtmp://localhost/stream. But it streams only the small part of file
that's been recorded before ffmpeg command started and then the ffmpeg
session terminates, but the camera is still recording and file is
getting filled with new data that I want to be streamed as well