What happens when I type just "crontab -"? The "e" didn't take before I hit Enter. It just moved the cursor to the next line and I had to Ctrl+C to exit, but I'm not sure what it did exactly. I'm on Linux CentOS 6.3.
That actually depends on what you did after that.
crontab - is interpreted as a variation on the
crontab file invocation, where you change the current user's crontab with that contained in the specified file.
- in this case, as is common practice, means to read from
stdin instead of an actual file.
The result of this is that if you pressed ctrl-c or otherwise aborted crontab nothing happened. On the other hand, if you pressed ctrl-d (essentially
eof), ending the input normally, then the crontab was replaced by whatever you had entered previous to that (possibly emptying it if nothing had been entered).