strtol() function in C++ STL
The strtol() function is a builtin function in C++ STL which converts the contents of a string as an integral number of the specified base and return its value as a long int. Syntax:
strtol(s, &end, b)
Parameters: The function accepts three mandatory parameters which are described as below:
- s: specifies the string which has the representation of an integral number.
- end: indicates where the conversion stopped, refers to an already allocated object of type char*. The value of the end is set by the function to the next character in s after the last valid character.It can also be a null pointer, in which case it is not used.
- b: specifies to the base of the integral value.
Return Value: The function returns value of two types:
- If a valid conversion occurs, then a long int value is returned.
- If no valid conversion happens, then 0 is returned.
Below programs illustrate the above function. Program 1:
CPP
// C++ program to illustrate the // strtol() function when decimal base #include <cstdlib> #include <cstring> #include <iostream> #include <string> using namespace std; int main() { int b = 10; char s[] = "6010IG_2016p"; char * end; long int n; n = strtol (s, &end, b); cout << "Number in String = " << s << endl; cout << "Number in Long Int = " << n << endl; cout << "End String = " << end << endl << endl; // the pointer to invalid // characters can be null strcpy (s, "47"); cout << "Number in String = " << s << endl; n = strtol (s, &end, b); cout << "Number in Long Int = " << n << endl; if (*end) { cout << end; } else { cout << "Null pointer"; } return 0; } |
Output:
Number in String = 6010IG_2016p Number in Long Int = 6010 End String = IG_2016p Number in String = 47 Number in Long Int = 47 Null pointer
Program 2:
CPP
// C++ program to illustrate the // strtol() function #include <cstdlib> #include <cstring> #include <iostream> using namespace std; int main() { char * end; cout << "489bc" << " to Long Int with base-4 = " << strtol ("489bc", &end, 4) << endl; cout << "End String = " << end << endl; cout << "123s" << " to Long Int with base-11 = " << strtol ("123s", &end, 11) << endl; cout << "End String = " << end << endl; cout << "56xyz" << " to Long Int with base-36 = " << strtol ("56xyz", &end, 36) << endl; } |
Output:
489bc to Long Int with base-4 = 0 End String = 489bc 123s to Long Int with base-11 = 146 End String = s 56xyz to Long Int with base-36 = 8722043
Program 3:
CPP
// C++ program to illustrate the // strtol() function when base is 0 #include <cstdlib> #include <iostream> using namespace std; int main() { char * end; // octal base cout << "312gfg" << " to Long Int with base-0 = " << strtol ("312gfg", &end, 0) << endl; cout << "End String = " << end << endl << endl; // hexadecimal base cout << "0q15axtz" << " to Long Int with base-0 = " << strtol ("0q15axtz", &end, 0) << endl; cout << "End String = " << end << endl << endl; // decimal base cout << "33ffn" << " to Long Int with base-0 = " << strtol ("33ffn", &end, 0) << endl; cout << "End String = "; return 0; } |
Output:
312gfg to Long Int with base-0 = 312 End String = gfg 0q15axtz to Long Int with base-0 = 0 End String = q15axtz 33ffn to Long Int with base-0 = 33 End String =
Program 4
CPP
// C++ program to illustrate the // strtol() function for invalid // conversions and leading whitespaces. #include <cstdlib> #include <iostream> using namespace std; int main() { char * end; cout << "22abcd" << " to Long Int with base-6 = " << strtol (" 22abcd", &end, 6) << endl; cout << "End String = " << end << endl << endl; cout << "114cd" << " to Long Int with base-2 = " << strtol (" 114cd", &end, 2) << endl; cout << "End String = " << end << endl << endl; cout << "e10.79" << " to Long Int with base-10 = " << strtol ("e10.79", &end, 10) << endl; cout << "End String = " << end << endl << endl; return 0; } |
Output:
22abcd to Long Int with base-6 = 14 End String = abcd 114cd to Long Int with base-2 = 3 End String = 4cd e10.79 to Long Int with base-10 = 0 End String = e10.79