Reading in multiple characters, and determine whether positive, negative, and value:
int sign = 1;
ch = getchar(); //look at first char (might be a sign indicator)
if((ch == '-') || (ch == '+')) //consume first char if either `-` or `+`
{
if(ch == '-') sign = -1;
}
else //first char non-sign - handle as digit
{
if (ch > '9' || ch < '0')
continue; // or print an error and exit
i *= 10;
i += ch - '0';
}
while ((ch = getchar()) != '\n') //get remaining chars (assume no embedded sign chars)
{
if (ch > '9' || ch < '0')
continue; // or print an error and exit
i *= 10;
i += ch - '0';
}
i *= sign; //apply sign to value