How to give a pattern for new line in grep?

try pcregrep instead of regular grep:

pcregrep -M "pattern1.*\n.*pattern2" filename

the -M option allows it to match across multiple lines, so you can search for newlines as \n.

grep patterns are matched against individual lines so there is no way for a pattern to match a newline found in the input.

However you can find empty lines like this:

grep '^$' file
grep '^[[:space:]]*$' file # include white spaces

Thanks to @jarno I know about the -z option and I found out that when using GNU grep with the -P option, matching against \n is possible. :)

Example:

grep -zoP 'foo\n\K.*'<<<$'foo\nbar'

Result:

bar

Example that involves matching everything including newlines:

.* will not match newlines. To match everything including newlines, use¹(.|\n)*:

grep -zoP 'foo\n\K(.|\n)*'<<<$'foo\nbar\nqux'

Result:

bar
qux

¹ Seen here: https://stackoverflow.com/a/33418344

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