Thread: parsing command line

Hi there,

I have done a fair amount of research in order to figure out how to parse a command line for, say, and integer. The code below almost works, except when the user types in, for example, "4s". The result is that find_this_number gets assigned 4, whereas I would prefer to reject the input "4s" because the string does not represent an integer.

Some people have recommended using the boost library, but I would like to know if there is a way to do this using either strict C or the STL libraries only. Can you please help? Thanks!

Aaron

insert

Code:

string cmd_line = " ";
string cmd = " ";
int find_this_number = 0;


// Read in what-ever the user typed in...
getline(cin, cmd_line);
istringstream ss(cmd_line);


// Get the first word in the string
getline(ss, cmd, ' ');


// Check whether the user typed in an integer
stringstream scmd(cmd);
if ((scmd >> find_this_number).fail() )
    {
        cin.clear();
        cout << "oops, you typed: " << cmd << endl;
    }
    else
    {
        cout << "The number is: " << find_this_number << endl;
    }

Or you could use std::string.find_first_not_of() to check that the entire string doesn't contain any letters, or whatever else is invalid.

Also note: Most people consider the "command line" to be the variables passed to your program when you start it, not the use of an input stream.

Jim