.extract file [+off][-off][len]
 [-f] [-o file] [-a file]
 [-m addr] [-ml linaddr]
 [-mp pnum] [-mb bnum]

input:
  file = input file
  +off = byte offset from start
  -off = byte offset from end
   len = length in bytes

output:
  -f  = overwrite permitted
  -o  = write to out file
  -a  = append to out file
  -m  = copy to 64k addr
  -ml = copy to linear addr

no -o,-a,-m* generates hexdump

extract v1.1 zx-next z88dk.org
