use sed when ....

# insert a blank line above every line which matches "regex"
 sed '/regex/{x;p;x;}' OR  sed '/regex/{x;G;}'

# 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;}'

# remove the header of a file

sed '/1,1d' filename