cgi integration question

[Ken]

"Gerhard Häring" <gerhard.haering at opus-gmbh.net> wrote in message
news:slrnaqdigu.164.gerhard.haering at haering.opus-gmbh.net...
> [Broken Outlook Express quoting manually repaired, setting
> textwidth to 65 to help your craps oftware not mess up]
>
> Ken <ken at hotmail.com> [2002-10-11 12:34 GMT]:
> > "Gerhard Häring" <gerhard.haering at opus-gmbh.net> wrote:
> >> Ken <ken at hotmail.com> [2002-10-11 12:03 GMT]:
> >> > [...] I have 2 sets of code. Python is used to display
> >> > interface and C++ is used for backend execution. The
> >> > executed result is saved to file so the python can read it
> >> > and display back on the screen. [...]
> >>
> >> No need for intermediary files, just use os.popen*.
> >>
> >> Here's a simple example:
> >>
> >> >>> import os
> >> >>> outf, inf = os.popen2("cat")
> >> >>> print >>outf, "hi"
> >> >>> outf.close()
> >> >>> print inf.read()
> >> hi
> >>
> >> outf is a stream to write to your child process (in this example,
> >> the Unix cat utility, which will just duplicate on stdout what it
> >> gets on stdin). After writing the "parameters" to cat's stdin, I
> >> close it (don't ask me why that's necessary, but this is the way it
> >> works :-D). Then, I read the whole output of cat and print it.
> >
> > Hi, can you explain what is "inf" and "popen2" in:
> > outf, inf = os.popen2("cat")   ?
>
> os.popen2 is a function in the os module. It gets one parameter:
> the executable you want to run as a child process. It returns a
> tuple of two file objects:
>
> * The first file object is connected to the
>   input stream of the child process, i. e. you can WRITE to it.
>
> * The second file object is connected to the output stream of the
>   child process, i. e. you can READ from it.
>
> > Is "cat" suppose to be a program name for me to call?
>
> Yeah. As you seem to use Windows (with a b0rken newsreader), you
> won't have a 'cat' program. But you will have a 'sort' program,
> so you can try the following:
>
> >>> import os
> >>> outf, inf = os.popen2("sort")
> >>> print >>outf, "Mark"
> >>> print >>outf, "Joe"
> >>> print >>outf, "Marvin"
> >>> outf.close()
> >>> lines = inf.readlines()
> >>> inf.close()
> >>> print lines
> ['Joe\n', 'Mark\n', 'Marvin\n']

Will argc[1] = "Mark", argc[2]="Joe" and argc[3]="Marvin" in this example?

Does "lines = inf.readlines()" read out what is exactly printed out from the
return value of the main method or does it catch out what is printed out
from the cout<< command?
Eg:, if I have a command line:

cout<<"hello world"<<"hi"<<endl;

will it appear as ['hello world', 'hi'] or ['hello', 'world', 'hi']? will it
have '\n' automatically appended to it?




> > So.... if I get the idea right, my program should look like this:
> > import os
> > outf, inf = os.popen2("cat")
>
> # Obviously, replace 'cat' with the path to your compiled C++
> # application.
>
> # This send input to the C++ program:
>
> > print >>outf, "hi"
>
> > outf.close()
>
> > print inf.read()  # does this mean  read from file?
>
> Yep.
>
> > and the backend c++ program look somethingl like this:
> > executable filename: cat
> >
> > #include <iostream>
> > using namespace std;
> >
> > int main (int argc, char** argv) {
> >       cout << "value from argv"<< endl;
> >       return 0;
> > }
> >
> > Still don't get how values are passed to the backend though....can you
> > please explain.... : (
>
> In the Python script, you send the paramters to the C++ program
> by writing to its stdin. Then, the C++ program does its job, and
> when it's ready writes its output on stdout. See above for how to
> do the Python script, and here's a simplistic C++ 'backend'
> program:
>
> /**
>  * doubler.cc - Reads one line from stdin, then returns the
>  * "doubled" string on stdout.
>  */
>
> #include <iostream>
> #include <string>
>
> using namespace std;
>
> int main(int argc, char** argv) {
>     string s;
>
>     cin >> s;
>
>     cout << s + s;
>
>     return 0;
> }

 ['ss']  or  ['s', 's'] or  ['s\n', 's\n'] ?



>
>
> Alternatively, you could send over commandline arguments and
> parse these in the C++ app.
>
> HTH,
>
> -- Gerhard

Thanks