On Thu, 18 Jan 2001, Hal Burgiss wrote:
>
> Is the below expected behavior? or bug? Values assigned to variables
> within the loop, are not visible outside the loop. Using something
> like 'while true' works as I would expect.
>
>
> #!/bin/bash
> ## script: testing
> ## test variable visibility
> num=0
> echo 1 > tmp
> cat tmp |while read line ; do
> num=1
> echo $num
> done
> echo $num
>
> #--- eof testing
The reason is because the "while" loop is run in a
sub-process and any variables assigned there are lost...
but there is another way as follows:
#!/bin/bash
## script: testing
## test variable visibility
num=0
echo 1 > tmp
while read line
do
num=1
echo $num
done < tmp
echo $num
The above will accomplish the same thing by redirecting
stdin from "tmp" for the "while" loop, preventing a fork.
Remember that a "|" will always cause a subprocess to be
forked
--
John Darrah (u05192) | Dept: N/C Programming
Giddens Industries | Ph: (425) 353-0405 #229
PO box 3190 | Ph: (206) 767-4212 #229
Everett WA 98203 | Fx: (206) 764-9639
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