issues with c++ executbale

Question

Hi, I have c++ generated executable in solaris 8. the problem i am having is that this executable uses a cmd line param to run.

for example,

$ myprog 123412341234AB 

this is a valid 14 digit hexdecimal value. however, if for some reason there are symbols like ^ > < >> << & etc then the program does not behave properly per say. i am not talking core dumps per say but for example one of the checks i do is via isxdigit. apparently its not good enough to catch something like 1234123412341^ or 12341234(12341

so i am just trying to see if i can detect all these symbols in an effort to just exit properly. i mean some of these symbols have special meaning in unix and i guess that is why the prog does not understand how to handle it.

any thoughts on how to address this ? do i just try to find all these symbols and the moment i detect them in the cmd like i just exit out with an error message? how would i go about doing this?

i am using std::string. So maybe a list like !@#$%^&*()<><<>> etc where i can detect and get out. i am not sure if there is an easier way to do this so unix does not think i am giving it a system command when in fact its just an input to a program albeit it just happens to be a wrong/invalid input.

Answer 1

Just to address one part of the question, you could make a "isxstring" function like this:

bool isxstring(const std::string &s) {
    for(std::string::const_iterator it = s.begin(); it != s.end(); ++it) {
        if(!isxdigit(*it)) {
            return false;
        }
    }
    return true;
}

If you aren't doing something at least similar to this, then you aren't properly checking if every character is a hex-digit.

This would also likely be a valid definition:

bool isxstring(const std::string &s) {
    return s.find_first_not_of("0123456789abcdefABCDEF") == std::string::npos;
}

Answer 2

These characters are special to the command shell, and are being stripped off before your program even starts. Read up on quoting or escaping special characters for your shell.

Answer 3

You can't fix this by modifying your program -- those special characters are being interpreted by the shell before your code ever sees them.

You can prevent this by single-quoting the command-line argument:

myprog 'some_string_<with_special&>!chars'

or by escaping the special characters (by preceding each one with a backslash):

myprog some_string_\<with_special\&\>\!chars