To calculate the average or the maximum of the second column of data files, do awk '{sum += $2} END {printf ("%f\n", sum/NR)}' $1 or awk 'BEGIN {max = 0} {if ($2>max) max=$2} END {print max}' $1 The latter one is particularly useful for a quick-and-dirty plot of normalized spectra with gnuplot. ---- The easiest way to get the geometry of an image is identify -format "%wx%h\n" * ---- To enable applications requiring X to be started with root rights without having access to kdesu or gksu, steal the magic cookie from your users 😄 xauth add `xauth -f ~user/.Xauthority list $DISPLAY`