Question

In 2 parts of the C++/CLI code I’m working on, the program needs to run a different executable and have its STDOUT output redirected to a file. Its being attempted in 2 different ways, and only one of the 2 currently works. The program is being run on Windows XP.

The first section assembles a long char* that ends up looking something like this:

char* exepath = "start/B /D\\root\\bin \\root\\bin\\process.exe 1>\\root\\logs\\process_STDOUT.txt"

Then the code simply calls

Status = system(exepath);

This works fine: It both runs process.exe and creates the process_STDOUT.txt file as expected.

The second section tries to do the same using a ProcessStartInfo object instead. It successfully starts process.exe, but has not been creating the redirected output .txt file. Here is a simplified version of that code:

 Process p = gcnew Process();
 ProcessStartInfo^ s = gcnew ProcessStartInfo();
 s->FileName         = "\\root\\bin\\process.exe";
 s->WindowStyle      = ProcessWindowStyle::Hidden;
 s->CreateNoWindow   = true;
 s->UseShellExecute  = false;
 s->Arguments        = "1>\\root\\logs\\process_STDOUT.txt";
 p->StartInfo        = s;
 p->Start();

Am I doing something wrong with this code? And if not, is going back to just calling system(exepath) my only option or are there any others?

Answer 1

The system function invokes the system’s command-line interpretter, which on Windows is usually cmd.exe. That’s the program that parses the I/O-redirection syntax. The program you’re starting has no idea what > means; it interprets that as the first character of an actual command-line argument. (Think about it — have you ever written command-line-redirection code in your command-line programs? No, of course not. Neither did the author of process.exe.)

So that’s why your ProcessStartInfo method doesn’t redirect I/O. For that, see the question here about redirecting stdin and stdout in .Net.

Since you’re redirecting output to a file anyway, your current system code should be fine. The more programmatic ways of redirecting are necessary when you want to collect the output within your program instead of a file.