POSIX says that stderr shouldn't be "fully buffered" https://pubs.opengroup.org/onlinepubs/9699919799/functions/stdin.html https://pubs.opengroup.org/onlinepubs

POSIX says that stderr shouldn't be "fully buffered" https://pubs.opengroup.org/onlinepubs/9699919799/functions/stdin.html https://pubs.opengroup.org/onlinepubs/9699919799/functions/s... but I believe that allows for line buffering. Its terminology can be found here: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stdio.h.html https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/st... (look for _IOFBF).