piping an email message

[Alessio Pace]

Gerhard Häring wrote:

> Alessio Pace wrote:
>> Hi, I am writing a filter for the emails, I need it to pass through stdin
>> and then go via stdout.
>> 
>> Would this piece of code be okay to let just pass the message through the
>> pipe correctly?
>> 
>> # file 'pipe.py'
>> import email
>> import sys
>> 
>> def main():
>>     stdin_message = sys.stdin.read()
>>     msg = email.message_from_string(stdin_message)
>>     sys.stdout.write(str(msg))
>> 
>> if __name__ == '__main__':
>>     main()
> 
> The problem with this code is that it needs to read the entire message
> into memory. For 90 % of the messages, this should be no problem, but
> for the few multi-megabyte messages that you'll probably process, it
> will have negative impacts on the system performance.
> 
> I'd rather do something like:
> 
> #v+
> CHUNK_SIZE = 1024
> 
> while True:
>      chunk = sys.stdin.read(CHUNK_SIZE)
>      if not chunk: break
>      sys.stdout.write(chunk)
> #v-
> 
> Now that you know how to do it properly, you can use the relevant
> library function in the first place :-)
> 
> #v+
> import shutil
> shutil.copyfileobj(sys.stdin, sys.stdout)
> #v-
> 
> As you'll read strings, anyway, the explicit conversion to string using
> str() in your above code is superfluous, btw.

Mine was an example. In the real application I would modify the message read
from stdin and then write it to stdout. 
Thanks for the rest

> 
> -- Gerhard

-- 
bye
Alessio Pace