TIL that bash’s echo built-in actually checks if its write() to stdout actually wrote the full string or not, and if not will dutifully try to write the rest of the data again. It also ignores SIGINT and SIGTERM while doing this. This is fine, but if you happen to have a bug in your kernel driver that makes a write to a sysfs file return less than what was passed in, echo blah > /sys/… will hang and you’ll be confused. /bin/echo also retries the write indefinitely but can at least be Ctrl-C’d.