Hello


i've tried to export a variable from within a 'command| while... '
loop. The only way i figured out to do this is using a fifo (i've decided
to use a fifo instead of generating tempfiles via mktemp) .

The Script would look like this

#!/bin/bash

sock=/tmp/$RANDOM

if [ ! -S $sock ];then
/usr/bin/mkfifo $sock
fi

var=1
echo "Value before $var"

/bin/cat `pwd`/test.txt | while read line;do
if [ "`echo $line|/bin/grep XYZ|wc -l`" -ge 1 ];then
((var++)) && echo $var > $sock &
fi
done

var=`more < $sock`
echo "Value afer loop $var"
rm $sock

Is this the only way to the solution or are there other "workarounds"
known ?

Thanks in advice
Daniel

Daniel Hagen wrote:
> Hello
>
>
> i've tried to export a variable from within a 'command| while... '
> loop. The only way i figured out to do this is using a fifo (i've decided
> to use a fifo instead of generating tempfiles via mktemp) .
>
> The Script would look like this
>
> #!/bin/bash
>
> sock=/tmp/$RANDOM
>
> if [ ! -S $sock ];then
> /usr/bin/mkfifo $sock
> fi
>
> var=1
> echo "Value before $var"
>
> /bin/cat `pwd`/test.txt | while read line;do
> if [ "`echo $line|/bin/grep XYZ|wc -l`" -ge 1 ];then
> ((var++)) && echo $var > $sock &
> fi
> done
>
> var=`more < $sock`
> echo "Value afer loop $var"
> rm $sock
>
> Is this the only way to the solution or are there other "workarounds"
> known ?
>
> Thanks in advice
> Daniel

Could you not use process substitution, which has the same effect but
avoids the use of the sub-shell? The while would take the form of:

while read line
do
....

done < <(/bin/cat/ $(pwd)/test.txt)

Note that spacing between < < and no space between <( is important on
the done.

See http://tldp.org/LDP/abs/html/process-sub.html for more.

Geoff