See clientuser.h for a list of ClientUser's virtual functions. The 'p4 fstat' command is a combination of 'p4 files', 'p4 have', and 'p4 opened'. It may change over time. To view tabular output from the command line, pass the -Ztag flag to 'p4'. These flags allow changes to the form to occur between separate invocations of the p4 client program, rather than during a single invocation.
All form related commands can send back to the API a descriptor of the form.
This descriptor can be used with the Spec support in spec.h to parse forms into constituent variables and to format them from their constituent variables. The default implementation returns a FileSys object, described in the included file filesys.h.