Mask off features of a sequence emboss maskfeat -sequence $input1 -outseq $out_file1 -type "$type" -tolower $tolower -maskchar "$maskchar" -osformat2 $out_format1 -auto You can view the original documentation here_. .. _here: http://emboss.sourceforge.net/apps/release/5.0/emboss/apps/maskfeat.html