sed

# FILE SPACING: # double space a file sed G # double space a file which already has blank lines in it. Output file # should contain no more than one blank line between lines of text. sed '/^$/d;G' # triple space a file sed 'G;G' # undo double-spacing (assumes even-numbered lines are always blank) sed 'n;d' # insert a blank line above every line which matches "regex" sed '/regex/{x;p;x;}' # insert a blank line below every line which matches "regex" sed '/regex/G' # insert a blank line above and below every line which matches "regex" sed '/regex/{x;p;x;G;}' # NUMBERING: # number each line of a file (simple left alignment)....