On Wed, Dec 01, 2010 at 08:14:49AM -0500, ste...@syslang.net wrote:
> IFS=':' set -- aa:bb:cc:dd
> Instead, I have to say something like:
> oldIFS="$IFS"
> IFS=':'
> set -- aa:bb:cc:dd
> IFS="$oldIFS"
Neither one of these sets $1 to aa, $2 to bb and so on. They both set
$1 to aa:bb:cc:dd. IFS is not applied to a constant string, ever. It
is only applied to word-splitting that happens on various substitutions
(and lines of input handled by `read').
You probably fooled yourself by failing to quote $1 when you expanded it:
imadev:~$ IFS=:
imadev:~$ set -- aa:bb:cc:dd
imadev:~$ echo $1
aa bb cc dd
imadev:~$ echo "$1"
aa:bb:cc:dd
IFS is applied to the unquoted $1.
Now, let's pretend you asked a totally different question:
"I am trying to do this:
x=aa:bb:cc:dd
IFS=: set -- $x
Why doesn't IFS cause $x to be split into four words here?"
Here, IFS is not applied because the substitution of $x is performed
*before* the temporary environment is set up with IFS=: in it.
See http://mywiki.wooledge.org/BashFAQ/104 for a more wordy explanation.
