[GRASSGUI] Re: [GRASS-dev] d.rast.edit in wxgrass

[Michael Barton]

Split the command into a list by spaces. I realize that this is a problem
for any command with spaces in the arguments, but I know of no better way to
do this in this context outside of making users type any command as a Python
list. If we made people type ['g.region', 'rast=mymap', 'res=30'] instead of
g.region rast=mymap res=30, I don't think anyone would want to use the CLI.

This is one case where shell=True *is* legitimate. At least with a
shell, the user can use quotes or backslashes to include spaces in
arguments. Or you could implement equivalent functionality yourself.

IIUC, if I keep these as strings, I don't think I can use the cmd.Command
class and would have to do a custom version of Popen. Then I'd have to send
them through a different processing path rather than the RunCmd method that
everything else uses.

Michael

The latter is more work, but you can choose exactly which shell
functionality you want, e.g. allowing spaces (and other
metacharacters) without the other shell behaviour (sequences,
pipelines, redirection, variables, ....).

__________________________________________
Michael Barton, Professor of Anthropology and Director of Graduate Studies
School of Human Evolution & Social Change
Center for Social Dynamics and Complexity
Arizona State University

phone: [phone]
fax: [phone]
www: http://www.public.asu.edu/~cmbarton

[Glynn Clements]

Post by Michael Barton

Split the command into a list by spaces. I realize that this is a problem
for any command with spaces in the arguments, but I know of no better way to
do this in this context outside of making users type any command as a Python
list. If we made people type ['g.region', 'rast=mymap', 'res=30'] instead of
g.region rast=mymap res=30, I don't think anyone would want to use the CLI.

This is one case where shell=True *is* legitimate. At least with a
shell, the user can use quotes or backslashes to include spaces in
arguments. Or you could implement equivalent functionality yourself.

IIUC, if I keep these as strings, I don't think I can use the cmd.Command
class and would have to do a custom version of Popen. Then I'd have to send
them through a different processing path rather than the RunCmd method that
everything else uses.

One option is to call the shell explicitly, i.e.:

cmd.Command(['/bin/sh', '-c', cmdstr], ....)

or (on Windows):

cmd.Command(['cmd', '/c', cmdstr], ...)

Simply adding quoting to the existing implementation would probably be
preferable, though.

[Michael Barton]

Martin,

Is this change in cmd.Command easy to implement?

Michael

Post by Glynn Clements

Post by Michael Barton

Split the command into a list by spaces. I realize that this is a problem
for any command with spaces in the arguments, but I know of no better way
to
do this in this context outside of making users type any command as a
Python
list. If we made people type ['g.region', 'rast=mymap', 'res=30'] instead
of
g.region rast=mymap res=30, I don't think anyone would want to use the CLI.

This is one case where shell=True *is* legitimate. At least with a
shell, the user can use quotes or backslashes to include spaces in
arguments. Or you could implement equivalent functionality yourself.

IIUC, if I keep these as strings, I don't think I can use the cmd.Command
class and would have to do a custom version of Popen. Then I'd have to send
them through a different processing path rather than the RunCmd method that
everything else uses.

cmd.Command(['/bin/sh', '-c', cmdstr], ....)
cmd.Command(['cmd', '/c', cmdstr], ...)
Simply adding quoting to the existing implementation would probably be
preferable, though.

__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: [phone]
fax: [phone]
www: http://www.public.asu.edu/~cmbarton

[Glynn Clements]

Post by Michael Barton

Post by Glynn Clements

Post by Michael Barton

Split the command into a list by spaces. I realize that this is a problem
for any command with spaces in the arguments, but I know of no better way to
do this in this context outside of making users type any command as a Python
list. If we made people type ['g.region', 'rast=mymap', 'res=30'] instead of
g.region rast=mymap res=30, I don't think anyone would want to use the CLI.

This is one case where shell=True *is* legitimate. At least with a
shell, the user can use quotes or backslashes to include spaces in
arguments. Or you could implement equivalent functionality yourself.

IIUC, if I keep these as strings, I don't think I can use the cmd.Command
class and would have to do a custom version of Popen. Then I'd have to send
them through a different processing path rather than the RunCmd method that
everything else uses.

cmd.Command(['/bin/sh', '-c', cmdstr], ....)
cmd.Command(['cmd', '/c', cmdstr], ...)
Simply adding quoting to the existing implementation would probably be
preferable, though.

Martin,
Is this change in cmd.Command easy to implement?

The above isn't a change to cmd.Command(), but a change to how it is
used.

If you were to change cmd.Command(), the obvious change would be to
add a shell= parameter, which would be propagated directly to Popen().

Ultimately, if all you have is a single string provided by the user,
that string somehow has to be converted to a list of strings (as
that's what argv[] is).

The options are:

1. Split at each space.
2. As for 1, but with a quoting and/or escaping mechanism.
3. Use the shell.

1 fails to handle arguments which contain spaces. 2 solves this, but
requires some work. 3 gets the shell to do the work, but the cost is
that you get a lot of other stuff which you may not want
(substitution, redirection, loops, subshells, ...).