Re: [PATCH] Replace git-cvsimport with a rewrite that fixes major bugs.

On 01/03/2013 04:22 PM, Junio C Hamano wrote:

Antoine Pelisse [off-list ref] writes:

quoted

quoted

Doesn't Python come with a standard subprocess module that lets you
spawn external programs safely, similar to the way Perl's list form
open(), e.g. "open($fh, "-|", 'git', @args)", works?

... and of course a more boring "system('git', $subcmd, @args)", as well.

Python's os.system() takes exactly one argument, which must be a string,
and executes it in a subshell.  subprocess is indeed the way to go.

quoted

You mean something like this:

  p1 = subprocess.Popen([backend.command()], stdout=subprocess.PIPE)
  subprocess.Popen(["git", "fast-import", "--quiet"] + gitopts,
cwd=outdir, stdin=p1.stdout)

Assuming gitopts is a list rather than a string. (care must be taken
with backend.command() also)

Yes.

I vaguely recall that the subprocess module once used to be one
portability issue but that was between Python 2.3 and 2.4 or some
ancient history, and it should no longer be relevant.

subprocess was added in Python 2.4, and the above example should work
fine in any version >= 2.4.  But please note that other functions have
been added to the module since then, like check_call() (v2.5),
check_output (v2.7), and some methods were added to the Popen object in
v2.6.

Such things are documented pretty reliably in the Python library
documentation [1]; when in doubt, one can view older versions of the
library documentation, which are all available online [2].

Michael

[1] http://docs.python.org/2/library/
[2] http://www.python.org/doc/versions/

-- 
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/