[GRASS-dev] Python Scripting Library: mogrify command

[Massimiliano Cannata]

Thanks Glynn for clarification,
I will go with the make_command()...

Maxi



On 07/13/2011 11:26 AM, Glynn Clements wrote:
> Massimiliano Cannata wrote:
>
>> I was wandering: does exist a python::core function capable to mogrigy
>> the inputs of a run_command()?
>>
>> The mogrify function for psycopg2 is defined as follows:
>> "/Return a query string after arguments binding. The string returned is
>> exactly the one that would be sent to the database running the execute()
>> method or similar./"
>>   >>>  cur.mogrify("INSERT INTO test (num, data) VALUES (%s, %s)", (42,
>> 'bar'))
>> "INSERT INTO test (num, data) VALUES (42, E'bar')"
>>
>> ...so for GRASS it could be:
>>   >>>  grass.mogrify_command("r.univar",flags="g",map="test")
>> "r.univar -g map=test"
> make_command() returns an argument list, e.g.:
>
> 	>  import grass.script as grass
> 	>  grass.make_command("r.univar",flags="g",map="test")
> 	['r.univar', '-g', 'map=test']
>
> This is what all of the *_command() functions use to generate the
> argument list.
>
> Converting an argument list to a string is non-portable (/bin/sh has
> significantly different syntax to cmd.exe) and quite tricky unless
> you're willing to blindly quote everything to be on the safe side,
> e.g. (for /bin/sh):
>
> 	args = [arg.replace("'", "'\\''") for arg in args]
> 	cmdstr = "'" + "' '".join(args) + "'"
>
> It's much harder for Windows; see:
>
> 	http://msdn.microsoft.com/en-us/library/17w5ykft.aspx
>
> or escape_arg() in lib/gis/spawn.c, or list2cmdline() in Python's
> subprocess.py.
>
> Note that none of the *_command() functions construct a command
> string; they pass the argument list to subprocess.Popen() which
> eventually either passes it to execve() (on Unix) or uses
> list2cmdline() (on Windows).
>


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Dr. Eng. Massimiliano Cannata
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