Query related to conversion of segy file and .su files using Seismic Unix

hi

M using ubuntu 11.04....and has installed Seismic Unix on it....
I want to process some unprocessed segy data using Seismic Unix....
i have converted .segy file to .su using

segyread tape=file1.seg verbose=1 endian=0 | segyclean > smallfile.su

and got 3 files
-smallfile.su
-header
-binary
Now my queries are:

  1. How to verify that .su file created is valid or not?
  2. The .su file i got ....Is this the processed file?
    -Or the processing is yet to be performed on this .su file?
    -If it is processed how to read data from it?
  3. How to convert .su file to .seg file?

as when m running

segywrite < smallfile.su tape=file1.seg verbose=1 endian=0 | < processedfile.seg
its giving error as
segywrite: fgettr.c: bad first header
plzz help..
Regards..