brace expansion and variable expansion

[Gregory Seidman]

Brace expansion does not occur after variable expansion. I ran across
this when writing a script that needed to cat and sort a variable subset
of files, all of which reside in some directory. Consider this example:

#!/bin/bash

SELFILES="foo"

if test $# -gt 0
then
        SELFILES="$SELFILES,bar"
else
        SELFILES="$SELFILES,baz"
fi

cat /tmp/stuff/{$SELFILES} | sort > /tmp/stuff/foobarbaz

Instead of the expected results, which is that cat will be given two
file paths on its commandline, cat will be given a single argument of
either /tmp/stuff/{foo,bar} or /tmp/stuff/{foo,baz}. I've tested this on
version 2.05b on both MacOS X and Debian Linux (both x86 and PPC).

I am not subscribed to the bug-bash list, so any email intended for me
should be sent directly to me (as well as the list, if appropriate).

--Greg