Bash CD – Change Directory by Just Typing the Directory’s Name

The shell is a perfectly suitable tool for this job. Just take care not to mangle spaces and backslashes.

while IFS= read -r line; do
  if predicate "$line"; then printf '%s\n' "$line"; done
done

You could also use awk. Be sure to quote each line since it'll be passed to a shell (the snippet below puts single quotes around the line, and replaces single quotes in the line by '\''; \047 is '). Because each command invocation goes through a shell, I expect this to be slower than the pure shell method, even if awk is likely to be faster at parsing lines. But I haven't made any benchmarks.

awk '{quoted=$0; gsub(/\047/, "\047\\\\\047\047")}
     !system("predicate \047" $0 "\047")'

A quick trip to Google reveals this interesting approach: http://pebblesinthesand.wordpress.com/2008/05/22/a-srcipt-for-running-processes-in-parallel-in-bash/

for ARG in  $*; do
    command $ARG &
    NPROC=$(($NPROC+1))
    if [ "$NPROC" -ge 4 ]; then
        wait
        NPROC=0
    fi
done