Lighttpd

if lighttpd is running, and you try to start it again and it fails (because, for example it can't bind to an already in use port) a new pid file is created and overwrittes the pid file of the running lighttpd, but because the new lighttpd doesn't actually work, the new pid file stays empty.

#!ShellExample
# ./sbin/lighttpd -f conf/lighttpd.conf
# cat log/lighttpd.pid 
11794
# ./sbin/lighttpd -f conf/lighttpd.conf 
2006-08-01 20:08:16: (network.c.303) can't bind to port:  36663 Address already in use 
# cat log/lighttpd.pid 
# (^empty)

lighttpd process shouldn't create a new pid file if it didn't finish initializing and passsing all sanity tests.