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How do I call an executable from a C program (using winapi)?

Answer 1

+1 A:

Depends on how you measure efficiency. system() is programmer efficient.

Also see exec() and its many brothers.

wallyk 2010-02-15 21:44:25

Answer 2

+1 A:

CreateProcess() is a fairly low-level function for spawning subprocesses and may not be the most convenient option. For a C program where you need to read the output, consider popen() (note that the MS CRT places an underscore before its name):

FILE *f = _popen("dir", "r");
char buf[1000];
while (fgets(buf, sizeof(buf), f)) {
    // .. process output using stdio functions
}
_pclose(f);

Greg Hewgill 2010-02-15 21:45:03

popen() will not work from a GUI ap, only from a console. And please don't suggest while (!feof(f)) { - it's misused enough as it is.

anon 2010-02-15 21:46:59

I change the use of feof.

Greg Hewgill 2010-02-15 21:49:42

From MSDN "If used in a Windows program, the _popen function returns an invalid file pointer that will cause the program to hang indefinitely. _popen works properly in a Console application." See http://msdn.microsoft.com/en-us/library/96ayss4b%28VS.71%29.aspx

anon 2010-02-15 21:51:59

Answer 3

+2 A:

ShellExecute Can be used to create a process, its a more convenient way to pass arguments.

But if you want to use the output of the process then CreateProcess is probably your best bet

With CreateProcess you can pass a STARTUPINFO structure that can be used to pass a file pipe handle to Standard Out of the process.

CreateProcess will return a PROCESS_INFORMATION structure containing a HANDLE to the created process. That handle will become signalled when the process exits.

So You can WaitForSingleObject on the process handle to wait for the output to be complete.

Don't forget to CloseHandle on the process handle and thread handle when you are done.

John Knoeller 2010-02-15 21:55:01

If the process you want to start requires elevation (or Vista/7 automatically thinks it does, because of its filename or another heuristic) CreateProcess will fail and you'll need to handle that specific error. See http://msdn.microsoft.com/en-us/library/bb756945.aspx. ShellExecute or ShellExecuteEx are easiest, and the second lets you get process information that I think includes a process handle you can use as John describes.

David M 2010-02-18 00:00:41

Answer 4

+1 A:

The classic source for how to execute a Windows program and catch its output is this article on MSDN - it's actually not as complicated as it looks.

anon 2010-02-15 21:58:54

Answer 5

+1 A:

If you need full control (change std in/out etc), CreateProcess is your best option. If you are executing something specified by the user, you really need to use ShellExecute[Ex] since CreateProcess will fail for applications that require UAC elevation (ShellExecuteEx is also able to give you a handle to the child process when you start applications)

Anders 2010-02-15 22:14:31

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How do I call an executable from a C program (using winapi)?

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