On 05:15, Steven W. Orr wrote:
> * Why is it needed to use the unset?
> * What does unset -v do extra for me?
> * What bad things could happen if I don't do the unset?
Upvars makes use of unset's capability of traversing down the
call-stack:
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 # Outputs: a:2 b:1 c:0 d: e:0
# ^ ^ ^ ^ ^-- unset once (skipped t1)
# | | | +----- unset thrice to global
# | | +--------- unset twice till global
# | +------------- unset once till t1
# +----------------- unset not
See also: http://fvue.nl/wiki/Bash:_Unset
Freddy Vulto
http://fvue.nl
