Say I have this 857835 line file, containing stuff like this:
a1
rubbish1
rubbish2
rubbish3
rubbish4
a1
rubbish5
rubbish6
rubbish7
rubbish8
And I wish to remove all occurences of a1 and the next line (rubbish1 and rubbish5 in this example). How do I do it?
I've tried grep 'a1' -v -A1 to no avail, and my sed skillz are not really great :}
My Google-fu has not been able to help me this time, someone please help!
Try:
sed -e '/^a1$/,+1d' "filename"
This means from /^a1$/ to the next line, delete
The ^ and $ ensure you match the whole line, so a hidden a1 will not be matched.
^ and $ in that match, to force matching whole lines.
The following will work on non-GNU sed (the ,+1 address syntax is a GNU extension):
sed -e '/^a1$/,/^/d' my_file >my_filtered_file
"Starting at a line that reads exactly 'a1', and ending at the next line for which the beginning of the line exists (i.e. the next line), delete."
It's much less extensible than @asoundmove's answer, though, as deleting a different number of lines would take an entirely different script.
