How can I see when a process started, assuming I know the pid. (On Linux)
If you want only the start time, you can select the field and suppress the header by doing this:
ps -p YOURPID -o lstart=
the output will look like this:
Mon Dec 14 17:17:16 2009
ctime(3) format and you can parse it to split out the relevant parts.
Other start fields such as
start_time age the time (after 24 hours only the date is shown, for example).
You can, however, use them directly for recently started processes without further parsing:
ps -p YOURPID -o stime=
which would output something like: