Do variable interfere with background processing??

[shaokat]

I have this loop:
for transpart in a b c d
do
while read jpegimage pageseg
do
dest=$psegdir/$pageseg
if [ -f $extract/$jpegimage ] ; then
echo ConvertImages... converting $jpegimage

cat $extract/$jpegimage |jpegtopnm |pnmscale -xysize 2100 1680 |pgmtopbm -floyd |ppmtobmp -windows >$itmp/tempimg$transpart.bmp
mv $extract/$jpegimage $jpgtrash

~/gbm/gbmbpp -m bw $itmp/tempimg$transpart.bmp,inv $itmp/tempimg$transpart.pseg,pelx=6000,pely=6000
mv $itmp/tempimg.pseg $dest
else
print "$extract/$jpegimage $dest" >> ${filename}$transpart.missing
fi
done <${filename}trans.$transpart &
done
wait

Note that the inner while do ... done loop has '&' at the end indicating a background process.
The question: Will the variables interfere with each other as the four background processes run?

 

[cruel]

Someone please correct me if I am wrong.

Whatever you define outside of the loop or in the big loop will be effective in the inner loop. But if there is a new definition in the inner loop, the variable will be updated.

I am not sure, but I do not think background or not will make a difference. But session (like when you login or when you submit a script job) does. What I am saying is a background process does not create an independent session.

 

[PHV]

Since the inner loop use redirection, I think it is executed in a subshell.

Hope This Help
PH.