User can be anyone like student, author or teacher.
Each message is going to be separated by one or more new lines. If the user is there in the data file then it will take the word requested by the user and checks if the word is there in each of the messages posted on the message file. It prints all those messages that have the corresponding word in it. If there are no messages that has that word, then it prints that there are no recent messages corresponding to the word that the user has requested. This command can be extended in several ways.