I tried to use a sed command to extract alphanumberic names, one per line, from a file which also included comments (line starts with '#') and blank lines. I wanted to refer to each in a loop. I tried for MACHINE in `sed '/^[0-9A-Za-z][0-9A-Za-z]*/' ~/MPI-SRC/machine_names.txt` a little awkward because sed has no '+' to indicate "at least one alphanumeric". I got an error that there was no command given to sed. I thought it printed by default. I tried for MACHINE in `sed '/^[0-9A-Za-z][0-9A-Za-z]*/p' ~/MPI-SRC/machine_names.txt` and it printed all the names twice. Finally, I had to use for MACHINE in `sed -n '/^[0-9A-Za-z][0-9A-Za-z]*/p' ~/MPI-SRC/machine_names.txt` to suppress one copy. Why do I get "double or nothing"? -- -Dan Dr. Dan Martin, MD, CCFP, BSc, BCSc (Hon) GP Hospital Practitioner Computer Science grad student ummar143@cc.umanitoba.ca (204) 831-1746 answering machine always on