“A bug in kill was so surprising that, once I'd found it, I couldn't stop there. I needed to know how this bug came to be, and what had led the programmers so badly astray.”

alangrow.com blog · Alan Grow documents decade of kill command bugs in Ubuntu LTS releases

“This is really surprising. The kill program is 50 years old. Its spec is simple and stable. It's probably exercised a billion times a day.”

alangrow.com blog · Alan Grow documents decade of kill command bugs in Ubuntu LTS releases

“The optopt variable only holds the first character after the dash, not the whole negative pid. When character 1 is subtracted from character 0 we get a pid of -1.”

alangrow.com blog · Alan Grow documents decade of kill command bugs in Ubuntu LTS releases

“If pid equals -1, then sig is sent to every process for which the calling process has permission to send signals, except for process 1 (init).”

alangrow.com blog · Alan Grow documents decade of kill command bugs in Ubuntu LTS releases

“Process group signaling is in fact an awesome Unix innovation. I love it so much I added it to daemontools, where svc -+h now avoids orphans in a multiprocess service bounce.”

alangrow.com blog · Alan Grow documents decade of kill command bugs in Ubuntu LTS releases