With the sed command and find command you can replace all instances of a word or multiple words in multiple files Examples * To replace "oldWord" with "newWord" in all the files *.c : find . -name "*.c" -exec sed -i "s/oldWord/newWord/g" '{}' \; * To replace multiple words in files : 1. * Edit a temporary file "replace.txt" 2. * Add the words you want to replace on a column 3. * Add the replacement words in the second column 4. * For example word1 replacement1 word2 replacement2 5. * To do the task, replace all the words from the first column with the equivalent from the second column in all the files *.c, Execute : counter=0;for f in `cat replace.txt`;do replace[counter]=$f;counter=$counter+1;done;counter2=0; for ((a=0; a <= $counter-1;