Sometimes I run some_program | grep blah, but libc buffers the output because the program isn’t writing to a terminal (in libc, writing to a terminal is line-buffered but writing to a pipe/file isn’t). So the grep doesn’t work. It’s annoying and I’ve never known what to do about it.

I finally found a solution to this thanks to folks on Mastodon: unbuffer from the expect package. unbuffer program will open a new TTY, set the program’s stdout to that tty, and then write to the pipe itself and flush the output.

You can also use unbuffer to trick the program into thinking it’s writing to a TTY for some other reason.