Re: csh what is the path separator

From: Keith Thompson (kst-u_at_mib.org)
Date: 05/17/05 

Date: Tue, 17 May 2005 21:20:12 GMT

linq936@hotmail.com writes:
> some example as,
>
> set path = (path1 path2 $path)
>
> and I see also this,
>
> set path = (path1:path2:$path)
>
> I think I am confused. And it seems $path and $PATH sometimes are
> different.
>
> What should be the correct then?

$PATH is an environment variable, not specific to any particular
shell. Its value is a single string, consisting of a series of
directory names separate by ':' characters. For example:

    setenv PATH /usr/local/bin:/usr/bin:/bin

$path is a shell variable, specific to csh and tcsh. Its value is not
a single string; it's a list of strings, each of which is a directory
name. For example:

    set path = ( /usr/local/bin /usr/bin /bin )

The $PATH environment variable and the $path shell variable are
"magically" tied together by the shell, so that modifying one
automatically changes the other. Setting $path to a list value
implicitly sets $PATH to a single string consisting of the elements of
$path joined with ':' characters. Setting $PATH implicitly sets $path
to a list determined by splitting the value of $PATH, using ':' as a
delimiter.

If you do this:

    set path = ( /usr/local/bin:/usr/bin:/bin )

the result will be a valid value for $PATH, but an invalid vlaue for
$path. As it turns out, the shell uses $path when searching for
commands, so unless you actually have a directory named
"/usr/local/bin:/usr/bin:/bin", you won't be able to do much. Your
shell will be in an inconsistent state. You can fix it like this:

    setenv PATH $PATH

which forces the shell to reinitialize $path, but you should really
just avoid this situation in the first place. If you only set $path
to a list value, and/or only set $PATH to a string with ':'
delimiters, you don't need to care about ugly details.

"man csh" for more information. 

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center             <*>  <http://users.sdsc.edu/~kst>
We must do something.  This is something.  Therefore, we must do this.

Relevant Pages
Loading