Print all lines between a searched pattern of a text file to different file

In practice, I'd probably use Aet3miirah's answer most of the time, and alexey's answer is wonderful for navigating through the lines (also, it works with less). OTOH, I really like another approach (which is kind of the reversed Gilles' answer):

sed -n '/dog 123 4335/,$p'

When called with the -n flag, sed does not print by default the lines it processes anymore. Then we use a 2-address form that says to apply a command from the line matching /dog 123 4335/ until the end of the file (represented by $). The command in question is p, which prints the current line. So, this means "print all lines from the one matching /dog 123 4335/ until the end."

cut -d / -f 4 file1.txt | paste -sd '|' | xargs -I{} grep -v -E {} file2.csv

Explanation:

cut -d / -f 4 file1.txt will select the hashes from the first file

paste -sd '|' will join all the hashes into a regular expression ex. H1|H2|H3

xargs -I{} grep -v -E {} file2.csv will invoke grep with the previous pattern as an argument, xargs will replace {} with the content of the STDIN

If you don't have paste you could replace it with tr "\\n" "|" | sed 's/|$//'