HOW CAN I SELECT AN UNIQUE STRING FROM A FIELD? ACTUALLY I WANT TO PRINT RECORDS THAT 2ND FIELD OF THAT HAVE ONE CHARACTER AND IT MUST BE "P"
AWK '$2~"[P]" {PRINT $0}' IN > OUT
BUT THIS CODE PRINT ALL RECORDS WHICH 2ND FIELDS OF THEM START WITH "P" AND MAY CONTAINS ANOTHER CHARACTER!