dealing with binary files

[Gerardo Herzig]

Tom Brown wrote:

>On Mon, 2008-01-07 at 11:57 -0200, Guilherme Polo wrote:
>  
>
>>2008/1/7, Gerardo Herzig <gherzig at fmed.uba.ar>:
>>    
>>
>>>Hi all. Im trying to read a binary data from an postgres WAL archive.
>>>If i make a
>>>xfile = open('filename', 'rb').xreadlines()
>>>line = xfile.next()
>>>
>>>i see this sort of thing:
>>>']\xd0\x03\x00\x01\x00\x00\x00\r\x00\x00\x00\x00\x00\x00JM//DI+,D\x00\x00\x00\x01$\x00\x00\x00\x7f\x06\x00\x00y\r\t\x00\x02\x0f\t\x00\x00\x00\x10\x00)\x00\x01\x00\x12\x08
>>>\x00^\xc2\x0c\x00\x08\x00\x00\x003001({\xe8\x10\r\x00\x00\x00\xe4\xff\xffI\x10?l\x01@\x00\x00\x00$\x00\x00\x00\x00\n'
>>>
>>>This file suppose to have some information about database activity, but
>>>at this point i cant do more than this, because i cant figure out what
>>>to do in order to have some 'readable' text.
>>>
>>>Im guessing is some C code, im reading the struct module to see if it
>>>helps, but im not into C programming, and im lost at the start of my
>>>problem.
>>>      
>>>
>>You are looking at the correct module, struct. But in order to
>>understand or even correctly extract data from a binary file, you need
>>to know its structure. There should be some document describing the
>>Postgre WAL file format.
>>
>>    
>>
>
>"The log record headers are described in access/xlog.h"
>
>http://www.postgresql.org/docs/8.2/interactive/wal-internals.html
>
>  
>
Yes Tom, my 'C' comes that far, cant do more, i get quickly 
overwelmed...Guess i will have to spend some time reading about it.
Thanks!

Gerardo