Industry guru Dave Taylor offers free tech support on a wide variety of technical and business topics, including HTML, Apple iPhone, online advertising, Cascading Style Sheets, Web design, management, Unix, Linux, search engine optimization, online dating, Mac OS X, shell script programming and Microsoft Windows.

How do I set my Terminal / shell PS1 prompt?

I have Mac OS X 10.5.8. When I try to change my unix shell prompt by putting the line:

export PS1='mac> '

into my .bash_profile, the prompt is changed but the cursor is in the first column (over the "m" of my prompt) and any typing overwrites the prompt.

Dave's Answer:

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!

Help others find this article at Del.icio.us, Digg, Netscape, Reddit, and Stumble Upon

Categorized: Mac OS X Help (Article 9116)
Tagged: bash, command line, linux, shell prompt, unix
Previous: Why don't my banner ad stats match Google Analytics stats?
Next: Why does email from my iPhone have the wrong name?

Subscribe!

Never miss another useful Q&A article again! Subscribe to AskDaveTaylor with Google Reader.

Comments

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

Posted by: Ken B at October 9, 2009 10:48 AM

Hi, I'm having the same problem with my command prompt, but my cat -v output appears to be ok with every line ending in ^M:

$cat -v ~/.bash_profile
export PS1="[\t] \w\n\u@\h\$ "^M
export CLICOLOR=1^M
export LSCOLORS=ExFxCxDxBxegedebegacab^M

What am I missing?

Posted by: John at October 10, 2009 4:51 PM

As Ken said, you don't want to have those ^M sequences. That's the problem. :-)

Posted by: Dave Taylor at October 10, 2009 7:54 PM

"tools that understand the Linux environment lurking underneath your Mac OS X world."

Dave, please print a correction here. There is no Linux environment under OS X. It's a Unix environment. Linux is a Unix-Like operating system. The above information has the potential to send unknowing users to Linux help sites and publications for their Mac, only to find out that the tools on a Linux distro may differ greatly from those on OS X. OS X is closer to BSD Unix, and even that's not a perfect match.

Again, please correct this for the sake of your readership.

Posted by: Dan at November 3, 2009 8:12 AM

Fair observation, Dan. I should probably say "Linux-like" since it's actually quite complicated to figure out the family tree and heritage of any given *nix.

The point of it was, though, that if you were to pick up a Linux book and/or visit some Linux help sites, you'd be able to glean quite a bit about how to work with Mac OS X on the command line. It's that Posix compliance bit and it's having the same shell and same basic commands.

Posted by: Dave Taylor at November 3, 2009 8:24 AM

I have something to say, now that you mention it, but ...

I do have a lot to say, and questions of my own for that matter, but first I'd like to say thank you for all your efforts on this Web site by buying you a cup of coffee!

I do have a comment, now that you mention it!