Delete rows that do not contain a specific value?

Question

linux

There was a need to delete all lines from 10 files that do not contain
uk.html?subid=adwords
What is the best way to do this? Plain text files, in UTF-8

Answer 1

single file:
all files in directory:

ls /path/to/dir/* | while read file; do sed -i '/uk.html?subid=adwords/!d' "${file}"; done

Answer 2

perl, awk, sed, grep -- choose what you like
for awk something like
For grep something like this:

grep -v "uk.html?subid=adwords" file > tmp && rm file && mv tmp file