I think most people will agree that unset is extremely surprising,
though they may point to different parts of it as the source of their
surprise.
8 years after Freddy Vulto's initial investigations, there are many
things I still don't understand. For example, consider this code
straight from his web site[1]:
=====================================================================
wooledg:~$ cat freddy
#!/bin/bash
a=0 b=0 c=0 d=0 e=0
_unset() { unset -v b c c d d d e; }
t1() {
local a=1 b=1 c=1 d=1
t2
}
t2() {
local a=2 b=2 c=2 d=2 e=2
_unset
echo a:$a b:$b c:$c d:$d e:$e
}
t1
wooledg:~$ ./freddy
a:2 b:1 c:0 d: e:0
=====================================================================
But if I make a tiny change to it (eliminating the _unset function which
*appears* to have no purpose), it has entirely different behavior:
=====================================================================
wooledg:~$ cat freddy2
#!/bin/bash
a=0 b=0 c=0 d=0 e=0
t1() {
local a=1 b=1 c=1 d=1
t2
}
t2() {
local a=2 b=2 c=2 d=2 e=2
unset -v b c c d d d e
echo a:$a b:$b c:$c d:$d e:$e
}
t1
wooledg:~$ ./freddy2
a:2 b: c: d: e:
=====================================================================
I don't understand the difference.
Does unset create some kind of "placeholder" in the current function
(but not in a caller)?
[1] http://fvue.nl/wiki/Bash:_Unset
