Find and Replace a word in A (all) File(s) Linux

• Find and Replace a word in a File 

[root@testserver01 opt ]#   sed -i 's/find_pattern/replace_pattern/g'  /opt/filename

• Find and Replace a word in all Files in a folder

[root@testserver01 opt ]# sed -i 's/find_pattern/replace_pattern/g'   /opt/*.filetype