In terminal, I can search to end of log faster than the data gets there

[The Question] *Is there some way to have the pipe/tee/write combo write lines immediately? ... if it can be done, what is the trade-off?* [The Backdrop] My script sends a keypress to the terminal, which is running app. That keypress causes app to write a *marker* to its log. The log is the *app's* normal screen output (timestamped lines). The log is being written via | tee -a log The marker *marks* the line I want; ie. the timestamped line *before* the marker. The problem is that when I then *immediately* search the log (using sed from the same script), it sometimes returns a previous marker, ie. the most recent marker has not been written to the log yet. I assume this is a buffering issue, but I'm in unknown territory with that. Not sure if it matters: The script is elisp. The terminal is emacs terminal emulator with a bash shell.