sed question...

[Howard Goldstein]

Gary Kline wrote:
> 	My earlier post about deleting the first N lines was answered by
> 	this one-liner site {below}.   I wasn't including any
> 	redirection; doing so finally resolved the problem.  Now I need
> 	to delete every line from the 19th or so to the last line.
> 	Question one, can anybody explain the following syntax?  What do
> 	"P", "D" "ba" represent, in other words?
> 
> 
>  # delete the last 10 lines of a file
>  sed -e :a -e '$d;N;2,10ba' -e 'P;D'   # method 1
>  sed -n -e :a -e '1,10!{P;N;D;};N;ba'  # method 2
> 
> 
> 	Question two, can sed do its thing inline?

Wouldn't it be easier to use  head -n 18 ?