How do I convert argv to lpCommandLine parameter of CreateProcess?

Question

Let I want to write an application, that launches another application. Like this:

# This will launch another_app.exe
my_app.exe another_app.exe 
# This will laun         


        

Answer 1

You can check out the below code if it suits your need, the txt array sz can be used as a string pointer. I have added code support for both Unicode and MBCS,

            #include <string>
            #include <vector>

            #ifdef _UNICODE
                #define String std::wstring
            #else
                #define String std::string
            #endif 

            int _tmain(int argc, _TCHAR* argv[])
            {
                TCHAR sz[1024] = {0};
                std::vector<String> allArgs(argv, argv + argc);

                for(unsigned i=1; i < allArgs.size(); i++)
                {
                    TCHAR* ptr = (TCHAR*)allArgs[i].c_str();
                    _stprintf_s(sz, sizeof(sz), _T("%s %s"), sz, ptr);
                }

                return 0;
            }

Answer 2

The definitive answer on how to quote arguments is on Daniel Colascione's blog:

https://blogs.msdn.microsoft.com/twistylittlepassagesallalike/2011/04/23/everyone-quotes-command-line-arguments-the-wrong-way/

I am reluctant to quote the code here because I don't know the license. The basic idea is:

for each single argument:
    if it does not contain  \t\n\v\", 
        just use as is
    else
        output "
        for each character
            backslashes = 0
            if character is backslash
                count how many successive backslashes there are
            fi
            if eow
                output the backslashs doubled
                break
            else if char is "
                output the backslashs doubled
                output \"
            else
                output the backslashes (*not* doubled)
                output character
            fi
        rof
        output "
    fi // needs quoting
rof // each argument

If you need to pass the command line to cmd.exe, see the article (it's different).

I think it is crazy that the Microsoft C runtime library doesn't have a function to do this.

Answer 3

There is no Win32 API that does the reverse of CommandLineToArgvW(). You have to format the command line string yourself. This is nothing more than basic string concatenation.

Microsoft documents the format for command-line arguments (or at least the format expected by VC++-written apps, anyway):

Parsing C++ Command-Line Arguments

Microsoft C/C++ startup code uses the following rules when interpreting arguments given on the operating system command line:

• Arguments are delimited by white space, which is either a space or a tab.

• The caret character (^) is not recognized as an escape character or delimiter. The character is handled completely by the command-line parser in the operating system before being passed to the argv array in the program.

• A string surrounded by double quotation marks ("string") is interpreted as a single argument, regardless of white space contained within. A quoted string can be embedded in an argument.

• A double quotation mark preceded by a backslash (\") is interpreted as a literal double quotation mark character (").

• Backslashes are interpreted literally, unless they immediately precede a double quotation mark.

• If an even number of backslashes is followed by a double quotation mark, one backslash is placed in the argv array for every pair of backslashes, and the double quotation mark is interpreted as a string delimiter.

• If an odd number of backslashes is followed by a double quotation mark, one backslash is placed in the argv array for every pair of backslashes, and the double quotation mark is "escaped" by the remaining backslash, causing a literal double quotation mark (") to be placed in argv.

It should not be hard for you to write a function that takes an array of strings and concatenates them together, applying the reverse of the above rules to each string in the array.

Answer 4

You need to recreate the command line, taking care of having all program name and arguments enclosed in ". This is done by concatenating a \" to these strings, one at the beginning, one at the end.

Assuming the program name to be created is argv[1], the first argument argv[2] etc...

char command[1024]; // size to be adjusted
int i;
for (*command=0, i=1 ; i<argc ; i++) {
   if (i > 1) strcat(command, " ");
   strcat(command, "\"");
   strcat(command, argv[i]);
   strcat(command, "\"");
}

Use the 2^nd argument of CreateProcess

CreateProcess(NULL, command, ...);