%3 cat cat myfile awk awk 'PAT { do something }' cat->awk grep1 grep '^bad' awk->grep1 grep2 grep '^good' awk->grep2 do do 'further processing' grep1->do awk2 awk ' $1='good' {    print /dev/stdout; next }{    print /dev/stderr }' do->awk2 awk2->awk STDERR sed sed 's/good/perfect/' awk2->sed sort sort sed->sort grep2->awk2