You've got the basics nailed, though there's a ton of cool things you can do with your shell prompt above and beyond what you're trying to accomplish. The problem you're having is that I'm going to guess that you're using a different editor, not one within the Terminal.app environment on your Mac OS X system, and it's saving the file with the wrong kind of end-of-line sequence.
Many editors have configuration options on file saving that let you choose Mac or MSDOS line ending sequences: I'll bet you have it set for the wrong one for this specific file. Try doing this:
cat ~/.bash_profile
next time you're running in Terminal and I'm pretty confident that it'll display incorrectly.
The real solution is to either use an editor within the Terminal environment (the two main choices are "vi" and "emacs", both of which are quite sophisticated editors) or to use a third-party tool like BBEdit or TextWrangler, tools that understand the Linux environment lurking underneath your Mac OS X world.
Once you've nailed this problem, here are a few fun things you can do with the command prompt in Bash:
| Sequence | Explanation |
|---|
| \h | the hostname up to the first `.' |
| \H | the hostname |
| \t | the current time in 24-hour HH:MM:SS format |
| \T | the current time in 12-hour HH:MM:SS format |
| \@ | the current time in 12-hour am/pm format |
| \u | the username of the current user |
| \w | the current working directory, with $HOME abbreviated with a
tilde |
| \W | the basename of the current working directory, with $HOME
abbreviated with a tilde |
| \! | the history number of this command |
| \$ | if the effective UID is 0, a #, otherwise a $ |
My command prompt, for example, is this:
PS1="\w (\!) \$ "
This gives me output like "~/bin (337) $ " when I'm in my "bin" directory, working. Experiment, play, you'll be surprised how helpful these can be once you really start digging into the command line!
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The problem with your "cat" command is that, generally, if the file has Windows' CRLF line endings, it will still look fine. Most Unix systems I use have a "-v" flag to cat which will show any control characters (aside from the newline) as caret-letter. So, if the example .bash_profile were in Windows format, using the command:
cat -v ~/.bash_profile
you would see:
export PS1='mac> '^M