Text Processing: Recursive search and replace

Recursive search with Grep

grep -rni 'string or regexp' *

Where:

* – will match to all files and directories (which doesn't start with ., alternatively you may need to use ./ to match everything within the current directory;
-r, --recursive – in this case works together with * (or ./);
-n, --line-number – output the line number where the match is found,
-i, --ignore-case – do case insensitive match.

SEARCHED="string or regexp"
REPLACEMENT="string"

Dry run:

grep -rlZ "$SEARCHED" * | xargs -0 sed 's/${SEARCHED}/${REPLACEMENT}/g'

grep -rlZ "$SEARCHED" * | xargs -0 sed 's/${SEARCHED}/${REPLACEMENT}/g' | grep "$REPLACEMENT"

Replace:

grep -rlZ "$SEARCHED" * | xargs -0 sed 's/${SEARCHED}/${REPLACEMENT}/g' -i.bak

Where:

grep: -Z, --null – a data line ends in 0 byte, not newline (null delimiter);
grep: -l, --files-with-matches – print only names of FILEs with selected lines;
xargs: -0 --null – items are separated by a null, not white-space; disables quote and backslash processing and logical EOF processing;
sed: s – substitute /old/new/, g – all matches to the end of the line; -i.bak do the changes in place and create a backup file.

Simple example:

grep -rliZ 'hw\.2022' | xargs -0 sed 's#hw\.2022#homework/hw.2022#g' -i.bak