#Use SED
sed -i 's/my/your/g' test.txt test2.txt test3.txt
#Use FIND and SED
find . -name *.txt -exec sed -i 's/my/your/g' {} \;
#Use AWK
awk '{sub(/{OLD_TERM}/,{NEW_TERM}); print}' {file}
awk '{sub(/my/,your); print}' test.txt
awk '{gsub(/i/,"a"); print}' test.txt
