New comment by Duncaen on mblaze repository https://github.com/leahneukirchen/mblaze/issues/203#issuecomment-798785916 Comment: This looks like a bug in musl, the second popen'ed process ends up inheriting the writing end of the first popen. > The popen() function shall ensure that any streams from previous popen() calls that remain open in the parent process are closed in the new child process. https://pubs.opengroup.org/onlinepubs/9699919799/ ``` echo "Hello\nWorld" | extrace busybox awk '{print $0 |"cat -n"; print $0 |"cat -n"}' ```