Record file format

Does anybody know the file format? that i recorded signals into files
and I want to read them for analysis. what is the format of the data
written/read by filesink/source block (I used GRC)
And I used the USRB source block and choose complex type of output >>>
So does the file i record are complex?(The signal that I received by
USRP are real signal(beacon signal))

and i saw that they are code to read the file from matlab named
read_*_binary.m and i see that thay got * = complex,float,short,char ,so
what kind of these type do i use or will i just use the same with what
kind of signal i receive? like i receive real signal so i use float ,
does it correct?

Thank you for every body in adviec