What happens when crontabs overlap?

Question

I'm coding in PHP and threads are a bit out of my league. I'd like to run the same script in parallel. Say my script runs for 2 minutes, and I run it every minute during a cronjob. What happens? Does the first one fall over when the second one runs, or do they just both hum along?

Answer 1

Both jobs "just hum along".

Answer 2

Both jobs will work in parallel as two different processes. Just be careful they do not use the same resource at the same time (say, a file). This can cause some nasty problems which are hard to debug.