sed 's/original_string/new_string/' file1 file2 file3 ...

-2 points

You can do

Code:
sed 's/original_string/new_string/' file1 file2 file3 ...

If the strings contain the character / you can use any other character
for delimiter.

On second thought this will send all the output to the screen.
So I guess you should do

Code:
sed 's/original_string/new_string/' file > tmp_file
mv tmp_file file

and repeat this for every file you want changed.

Created by ranipoojax