[GRASS-user] Using grass.run_commmand

[Glynn Clements]

Luisa Peña wrote:

> is there any difference, when it comes to processing, between run_command
> and read_command?

run_command() executes the command and waits for it to terminate; it
doesn't redirect any of the standard streams.

read_command() executes the command with stdout redirected to a pipe,
and reads everything written to it. Once the command terminates, it
returns the data written to stdout as a string.

> and from read_command  can I retrieve the error also?

None of the existing *_command functions redirect stderr. You can do
so with e.g.:

def read2_command(*args, **kwargs):
    kwargs['stdout'] = grass.PIPE
    kwargs['stderr'] = grass.PIPE
    ps = grass.start_command(*args, **kwargs)
    return ps.communicate()

This behaves like read_command() except that it returns a tuple of
(stdout,stderr) rather than just stdout.

-- 
Glynn Clements <glynn at gclements.plus.com>