Calling external program in C++

[Jon Slaughter]

is there a C++ method of calling an external executable program? I know you
can do it using C, but what about C++?

[Victor Bazarov]

Re: Calling external program in C++

Jon Slaughter wrote:[color=blue]
> is there a C++ method of calling an external executable program? I know you
> can do it using C, but what about C++?[/color]

Use the same way you know. C++ is often quite compatible with C in that
area. If you encounter a problem, come back and let's talk about it.

V

[Lemon tree]

Re: Calling external program in C++

"Jon Slaughter" <nobody@nowhere .com> ha scritto nel messaggio
news:10rrvqecbt ia878@corp.supe rnews.com...[color=blue]
> is there a C++ method of calling an external executable program? I know[/color]
you[color=blue]
> can do it using C, but what about C++?[/color]

I think that there is no standard way to do this...

So, in my opinion, the best way is to use the C -stylepossibly wrapped
inside a C++ method or something similar.

Andrea Sini

[Default User]

Re: Calling external program in C++

Jon Slaughter wrote:
[color=blue]
> is there a C++ method of calling an external executable program? I
> know you can do it using C, but what about C++?[/color]

Same way, system().




Brian

[Mike Wahler]

Re: Calling external program in C++


"Lemon tree" <lemon@tree.i t> wrote in message
news:M4ovd.2898 60$b5.14124045@ news3.tin.it...[color=blue]
> "Jon Slaughter" <nobody@nowhere .com> ha scritto nel messaggio
> news:10rrvqecbt ia878@corp.supe rnews.com...[color=green]
> > is there a C++ method of calling an external executable program? I know[/color]
> you[color=green]
> > can do it using C, but what about C++?[/color]
>
> I think that there is no standard way to do this...[/color]

Yes there is. Standard function 'system()'. But note
that its argument and actual functionality are implementation-
specific (e.g. not all implementations have the necessary access
to a command processor.
[color=blue]
>
> So, in my opinion, the best way is to use the C -style[/color]


'system()' is as much a part of the C++ standard library as
it is of the C standard library.
[color=blue]
>possibly wrapped
> inside a C++ method or something similar.[/color]

Why wrap it?

-Mike

[msalters]

Re: Calling external program in C++


Mike Wahler wrote:[color=blue]
> "Lemon tree" <lemon@tree.i t> wrote in message
> news:M4ovd.2898 60$b5.14124045@ news3.tin.it...[color=green]
> > "Jon Slaughter" <nobody@nowhere .com> ha scritto nel messaggio
> > I think that there is no standard way to do this...[/color]
>
> Yes there is. Standard function 'system()'. But note
> that its argument and actual functionality are implementation-
> specific (e.g. not all implementations have the necessary access
> to a command processor.
>[color=green]
> >
> > So, in my opinion, the best way is to use the C -style[/color]
>
> 'system()' is as much a part of the C++ standard library as
> it is of the C standard library.
>[color=green]
> >possibly wrapped
> > inside a C++ method or something similar.[/color]
>
> Why wrap it?[/color]

Wrap it so you can add arguments more easily; the C interface
of system has a horrible way to add arguments (memory fiddling).
std::string has a decent operator+(). So even
void system( std::string const& );
is a useful wrapper.

Regards,
Michiel Salters

[Mike Wahler]

Re: Calling external program in C++


"msalters" <Michiel.Salter s@logicacmg.com > wrote in message
news:1103023866 .888986.162720@ z14g2000cwz.goo glegroups.com.. .[color=blue]
>
> Mike Wahler wrote:[color=green]
> > "Lemon tree" <lemon@tree.i t> wrote in message
> > news:M4ovd.2898 60$b5.14124045@ news3.tin.it...[color=darkred]
> > > "Jon Slaughter" <nobody@nowhere .com> ha scritto nel messaggio
> > > I think that there is no standard way to do this...[/color]
> >
> > Yes there is. Standard function 'system()'. But note
> > that its argument and actual functionality are implementation-
> > specific (e.g. not all implementations have the necessary access
> > to a command processor.
> >[color=darkred]
> > >
> > > So, in my opinion, the best way is to use the C -style[/color]
> >
> > 'system()' is as much a part of the C++ standard library as
> > it is of the C standard library.
> >[color=darkred]
> > >possibly wrapped
> > > inside a C++ method or something similar.[/color]
> >
> > Why wrap it?[/color]
>
> Wrap it so you can add arguments more easily;[/color]

Huh? 'system()' takes exactly one argument.

[color=blue]
> the C interface
> of system has a horrible way to add arguments (memory fiddling).[/color]

Huh? 'system()' takes exactly one argument, and it is provided
the same as for any other function. No 'fiddling' needed.
[color=blue]
> std::string has a decent operator+().[/color]

So you want to concatentate strings. You can do this easily for
C-style strings with 'strcat()'.
[color=blue]
> So even
> void system( std::string const& );
> is a useful wrapper.[/color]

It would let you pass a std::string object, yes. How useful
that might be is imo a matter of opinion. One can already
supply the contents of a std::string to 'system()' via
std::string::c_ str().

-MIke

[jcoffin@taeus.com]

Re: Calling external program in C++

> is there a C++ method of calling an external executable program?[color=blue]
> I know you can do it using C, but what about C++?[/color]

Here's one possibility you might find interesting (this was a quick
hack at overhauling some code I wrote _years_ ago that used an
ostrstream, so it might benefit from some cleanup):

#include <sstream>
#include <cstdlib>

using std::ostringstr eam;

ostringstream &execute(ostrin gstream &s)
{
std::system(s.s tr().c_str());
return s;
}

ostringstream &operator<<(ost ringstream &s,
ostringstream &(*manip)(ostri ngstream &s))
{
return manip(s);
}

int main() {
ostringstream x;

x << "ls " << execute;

return 0;
}

If you want to see the original code, it's at:

http://groups-beta.google.com/group/comp.lang.c++/msg/a2940ddf50edf667

I have to admit that until I looked at the date on that post, I hadn't
quite realized how old this really was. :-)

--
Later,
Jerry.

The universe is a figment of its own imagination.

[jcoffin@taeus.com]

Re: Calling external program in C++

> is there a C++ method of calling an external executable program?[color=blue]
> I know you can do it using C, but what about C++?[/color]

Here's a possibility you might find interesting:

#include <sstream>
#include <cstdlib>

using std::ostringstr eam;

ostringstream &execute(ostrin gstream &s) {
std::system(s.s tr().c_str());
return s;
}

ostringstream &operator<<(ost ringstream &s,
ostringstream &(*manip)(ostri ngstream &s))
{
return manip(s);
}

int main() {
ostringstream x;

x << "ls ";
x << execute;

return 0;
}

This is a quick hack of some much older code that used an strstream; it
might benefit from further work. In case you case, the original code is
here:

http://groups-beta.google.com/group/comp.lang.c++/msg/a2940ddf50edf667

I must confess that I hadn't realized just HOW old this code was until
I looked at the date on that post...

--
Later,
Jerry.

The universe is a figment of its own imagination.

[jcoffin@taeus.com]

Re: Calling external program in C++

Okay, I'll make _one_ more try at getting this posted -- as they say,
third time pays for all....
[color=blue]
> is there a C++ method of calling an external executable program?
> I know you can do it using C, but what about C++?[/color]

Perhaps you'll find this an interesting possibility:

#include <sstream>
#include <cstdlib>

using std::ostringstr eam;

ostringstream &execute(ostrin gstream &s) {
std::system(s.s tr().c_str());
return s;
}

ostringstream &operator<<(ost ringstream &s,
ostringstream &(*manip)(ostri ngstream &s))
{
return manip(s);
}

int main() {
ostringstream x;

x << "ls ";
x << execute;

return 0;
}

--
Later,
Jerry.

The universe is a figment of its own imagination.