How to get the raw command line arguments

Question

I need to pass command line arguments from A.exe to B.exe. If A.exe with multi-args like

A.exe -a="a" -b="b"'

and I can use

BeginProcess("B.exe", **args!**)

to start B.exe. How can I get the raw command line arguments like

'-a="a" -b="b"'

Answer 1

If you are on Windows, you use GetCommandLine to get the raw command line.

Note that GetCommandLine also includes argv[0]. So you will have to go beyond argv[0] from the output of GetCommandLine before passing it to B.

This is some non-error checked code to do that

#include <string.h>
#include <windows.h>
#include <iostream>
#include <ctype.h>

int main(int argc, char **argv)
{
    LPTSTR cmd  = GetCommandLine();

    int l = strlen(argv[0]);

    if(cmd == strstr(cmd, argv[0]))
    {
        cmd = cmd + l;
        while(*cmd && isspace(*cmd))
            ++cmd;
    }

    std::cout<<"Command Line is : "<<cmd;

}

When I run the above program as A.exe -a="a" -b="b", I get the following output

A.exe -a="a" -b="b"
Command Line is : -a="a" -b="b"

Answer 2

Here is the one and only correct way to skip the executable name, based on Wine's implementation of CommandLineToArgvW:

char *s = lpCmdline;
if (*s == '"') {
    ++s;
    while (*s)
        if (*s++ == '"')
            break;
} else {
    while (*s && *s != ' ' && *s != '\t')
        ++s;
}
/* (optionally) skip spaces preceding the first argument */
while (*s == ' ' || *s == '\t')
    s++;

Note! Current Wine implementation, as of Feb 19 2'20 - git commit a10267172, is now moved from dlls/shell32/shell32_main.c to dlls/shcore/main.c.

Answer 3

The standard definition of main is

int main(int argc, char* argv[])

The argv variable contains the command-line arguments. The argc variable indicates how many entries in the argv array are used.

Answer 4

The raw string typed into the shell is converted by the shell into argv before your program begins running. I've never heard of an operating system or shell providing a "raw" command-line in addition to argv.

What if the user used quotes to pass a space character into your arguments? What if they used a backslash to escape a quote inside the quotes? Different shells may even have different quoting rules.

If you have a list like argv, you should try to find an API that accepts that rather than attempting to implement string processing which is only auxiliary to the actual goal. Microsoft is serious about security and they certainly provide something that doesn't require adding a security hole to your application.

I can't find documentation about any C/C++ API BeginProcess; I'm kind of assuming this is Windows but in any case you should double check your platform's reference manual for an alternative system call.