Fullpath in OS X

I am a few steps before starting my first real programming project and I am preparing my machine. I noticed that my fullpath (what I get when I "echo $PATH" in the terminal) does not look like a "normal" one (as I see "usr/bin" quite a lot of times). What does it mean? How does it affect my use of the terminal? And how, if, can I change it back to the default one?

EDIT: I can change it just by typing "PATH=the_name_of_the_path" but it's not permanent, if I quit the session I am running and start terminal again, what I get is "/Applications/lejos_nxj/bin:/us开发者_运维技巧r/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin" (and that's because I changed it some months ago so I could usel lejos_nxj, for a course at university). Is it better I change it back to the "normal" again or should I stop worrying about it? How can I change it anyway, in case I had to?

$PATH is a variable specifying a set of directories where executable programs are located. It's normal to see /usr/bin there.

Basically, if you type a command on the terminal, like cat for example, it's going to look for cat in those directories. This way, you don't have to specify the full path to all your frequently used commands.

Here is an example of a "normal" path on a new OS X 10.6 install:

/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/local/git/bin:/usr/X11/bin

If you see the same entries repeated again and again, then you probably have a mixup with your .bashrc vs. .bash_profile. You should set the PATH in the .bash_profile, not .bashrc, to avoid this.

$PATH under all *nixes is actually a list of colon-separated directories. Unless you see several times the /usr/bin entry, nothing's wrong (and even if you see it several times, it doesn't mean it's broken either).

At any rate, you should post what you get.

My path looks like this:

frak:~ seth$ echo $PATH
/usr/local/bin:/bin:/sbin:/usr/bin:/usr/sbin

Yours should look pretty much the same. Each directory is separated by ':'. However, even if you do have /usr/bin more than once, it won't make any difference.

Observe:

frak:~ seth$ whereis units
/usr/bin/units
frak:~ seth$ units attoparsecs/s m/s
    * 0.030856776
    / 32.407793

Add a /usr/bin again:

frak:~ seth$ PATH=$PATH:/usr/bin
frak:~ seth$ echo $PATH
/usr/local/bin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/bin

And everything still works fine:

frak:~ seth$ whereis units
/usr/bin/units
frak:~ seth$ units attoparsecs/s m/s
    * 0.030856776
    / 32.407793

PATH is a shell variable specifying where to find executables. For example, if you do a ftp (file transfer), the shell will look for the command ftp in those directories in your PATH variable before executing it. There's nothing wrong with that. If /usr/bin is not specified in your PATH, then everytime you need to use ftp, you need to give full path name , eg /usr/bin/ftp

Note that for a normal user, /usr/sbin should not be in PATH because those in /usr/sbin are mostly administrative commands.