[Tutor] Unix philosophy

David Rock david at graniteweb.com
Mon Nov 17 18:53:28 EST 2003

* Kalle Svensson <kalle at lysator.liu.se> [2003-11-17 20:17]:
> Hi!
> [Guillermo Fernandez Castellanos]
> > I was having a look at the UNIX philosophy and I readed that:
> > "Make every program a filter
> > This makes it easy to build a set of filter components into ``one
> > big filter.'' Programs can communicate by explicitly reading and
> > writing files; that is / much / more complex to manage, and requires
> > a lot of disk I/O for interim output. A set of filters may pass data
> > straight from memory buffer to memory buffer, avoiding disk
> > altogether."
> > 
> > I was wondering how I could be able to make my python programs work
> > in a filter mode?
> Basically, what you have to do is read input from stdin and write
> output to stdout.  That makes it possible to use it as a filter in a
> pipeline like
>   grep something < file | python myprog.py | lp
> or whatever.  The "|" signs here connect the first program's stdout to
> the second program's stdin.

Yes, but the question is "how" to make it do that ;-) 

I use the fileinput module to do this:

works great for all kinds of files, multiple files, stdin, etc.

David Rock
david at graniteweb.com
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