sed

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sed can be used to replace text in a file.

sed -i 's/old-string/new-string/g'  file-name.txt

g = Global, replace everything in a file.
s = substitute text
-i = update the file.

Delete lines matching string

To delete lines having a string and print the result.

sed '/string to match/d' file-name.txt

To update the file, use -i option

sed -i '/string to match/d' file-name.txt

Search & Replace using rpl