Some unix commands

To delete a Directory: rm -rf Directory_name

Appending a file to a mail: mail -s "title"  xx@xx.cm

Replacing a string in vi editor:    :%s/Old_String/New_String/g

Compress a file: tar cvf file.tar Directory_Name

Uncompress a file: tar xvf file.tar

To search for a string in vi editer: / 

To navigate the same search string in vi editor: + 3 (or) #