Ejemplo de llamada en un CGI perl usando ionice para definir la prioridad del proceso de ejecución. From http://manpages.courier-mta.org/htmlman1/ionice.1.html

ionice.sh

# ionice -c 3 -p 89 Sets process with PID 89 as an idle I/O process.
# ionice -c 2 -n 0 bash Runs 'bash' as a best-effort program with highest priority.
# ionice -p 89 91 Prints the class and priority of the processes with PID 89 and 91.

system ("ionice -c 2 -n 7 pdftk $tmp1 $tmp2 output -");