Run a external program.

MRAB python at
Sat Nov 14 20:53:50 CET 2009

Yasser Almeida Hernández wrote:
> Hi all!!
> I'm writing a script where i call a external program which receive some 
> arguments.
> One of this arguments is stored in a variable, that is passed as 
> argument as well:
> import os
> ...
> f = open(file1, 'r')
> s = 'command $f -i file2 -w 1.4 -o file3.out'
> os.system(s)
> ...
> When i run the script i get the next message...
> '-i: No such file or directory'
> ... with a obvious error in the exit of the program. If i remove the 
> option -i i get the same error with every option, even with those who 
> don't get any file as argument. (file2 exist).
> BUT, when i run the external program in a python shell, it works...
> What's wrong?
The name 'f' in the Python script exists only in Python and is unrelated
to the '$f' that the shell sees.

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