Parsing command line in MSVC

Question

Not really asking about parsing command line arguement but rather the code (C++) to read them in

I have wrote in MSVC2010. Select Project\DEbugging\Command Line Arguement), I have written the following

"testvid" 10000 15000

all separated by space

FOr my read in code, I have used string stream to read them in

string folder;
int begin;
int end;

if(argc = 4){
    std::stringstream ssArgConverter;

    folder = argv[1];

    ssArgConverter << argv[2];
    if(ssArgConverter >> begin)
    {
       // success
       ssArgConverter.str("");
    }

    ssArgConverter << argv[3];
    if(ssArgConverter >> end)
    {
       // success
       ssArgConverter.str("");
    }

}

HAve tested the program but I seem to have problem reading in the last argument. THe printed value for the argument in my program is

folder : testvid
begin  : 10000
end    : -89456273

Just cant figure out what is wrong. Need some help here. Thanks

Note: If the `ssArgConverter` fails for reading `argv[2]`, you still need to get it out of the error state (probably by `clear`ing the error state). — Thomas Matthews, Jan 13 '15 at 23:59
BTW, what were the issues when you singly stepped through each statement with the debugger? — Thomas Matthews, Jan 14 '15 at 00:00
Why are you assigning the value 4 to `argc` in your `if` statement? — Thomas Matthews, Jan 14 '15 at 00:01
I have 3 arguments and one function name... so I reckon the argc value to be 4 — user1538798, Jan 14 '15 at 00:05
under debugger... the arguments value seem to be correctly displayed but it somehow cant be read into the int iend — user1538798, Jan 14 '15 at 00:06
@user1538798: OK, but `if(argc = 4){` is assigning 4 to `argc`, whereas `if(argc == 4){` compares them. — indiv, Jan 14 '15 at 00:07
@indiv ooops...sorry...typo...you are right, it should be == 4... have mistyped it down here — user1538798, Jan 14 '15 at 00:08

score 1 · Answer 1 · edited May 23 '17 at 12:27

You need to clear your stringstream, not set its content to "".

string folder;
int begin;
int end;

if(argc == 4){
    std::stringstream ssArgConverter;

    folder = argv[1];

    ssArgConverter << argv[2];
    if(ssArgConverter >> begin)
    {
       // success
       ssArgConverter.str("");
       ssArgConverter.clear();
    }

    ssArgConverter << argv[3];
    if(ssArgConverter >> end)
    {
       // success
       ssArgConverter.str("");
       ssArgConverter.clear();
    }
}

EDIT: this question is pretty similar to: How to clear stringstream? and the accepted answer has a pretty good explanation.

So you actually should use .str("") or .str(std::string()) and .clear()

Thanks for the help! Didnt know that would need to have an additional .clear(). Have been just using the .str("") method whenever I am parsing data in a file and it has always work for me — user1538798, Jan 15 '15 at 02:23

Parsing command line in MSVC

1 Answers1