Issue when using _popen windows

Question

Hello i was try to run execute windows command using _popen and its work fine in vc++ in console.

while same code i do in c++ builder vcl form popen return null pointer ?

vc++

std::string exec(const char* cmd) {
    char buffer[128];
    std::string result = "";
    FILE* pipe = _popen(cmd, "r");
    if (!pipe) throw std::runtime_error("popen() failed!");
    try {
        while (!feof(pipe)) {
            if (fgets(buffer, 128, pipe) != NULL)
                result += buffer;
        }
    }
    catch (...) {
        _pclose(pipe);
        throw;
    }
    _pclose(pipe);
    return result;
}

c++ builder same as above

void __fastcall TForm2::btn_adb_readInfoClick(TObject *Sender) {
    const char* cmd = "D:\\adb\\adb.exe devices";
    char buffer[128];
    std::string result = "";
    FILE* pipe = _popen(cmd, "r"); // always null
    char* er = strerror(errno);
    try
    {
        if (!pipe) throw std::runtime_error("popen() failed!");
        while (!feof(pipe)) {
            if (fgets(buffer, 128, pipe) != NULL)
                result += buffer;
        }
    }
    catch (std::exception &ex) {
        _pclose(pipe);
        throw;
    }
    _pclose(pipe);
}

What is the value of `errno` immediately following the failed `_popen()`? — John Zwinck, Nov 23 '16 at 07:58
Unrelated to your problem, but please read [Why is “while ( !feof (file) )” always wrong?](http://stackoverflow.com/questions/5431941/why-is-while-feof-file-always-wrong) — Some programmer dude, Nov 23 '16 at 08:00

score 3 · Accepted Answer · answered Nov 23 '16 at 08:13

3

The MSDN documentation for _popen states:

If used in a Windows program, the _popen function returns an invalid file pointer that causes the program to stop responding indefinitely. _popen works properly in a console application.

I'm assuming that C++ Builder is creating a Windows application and not a Console application.

answered Nov 23 '16 at 08:13

dalle

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Yes it was windows application :) – user1965804 Nov 23 '16 at 08:16
What is the alternative for a Windows application? – Jonas Jan 30 '18 at 18:18
use a console application under the c++ builder – H.K Mar 31 '18 at 23:13

Issue when using _popen windows

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