[RndTbl] Another RE problem with sed

[Dan Martin]

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 at cc.umanitoba.ca
(204) 831-1746
answering machine always on