tr A-Z a-z < pipedoc.txt > tmp1.txt tr -cs a-z '\012' < tmp1.txt > tmp2.txt sort -u < tmp2.txt > tmp3.txt comm -23 tmp3.txt pipedict.txt tr A-Z a-z < pipedoc.txt | tr -cs a-z '\012' | sort -u | comm -23 - pipedict.txt