what - "show what versions of object modules were used to construct a file"
Synopsis Description Exit Status See Also Standards History Bugs
what [-qs] 
The what utility searches each specified file for sequences of the form "@(#)" as inserted by the source code control system. It prints the remainder of the string following this marker, up to a NUL character, newline, double quote, ">" character, or backslash. The following option is available:
The following option is available: