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atol() - Convert String to Long Integer - C++ Utility Functions Tutorial

atol() - Utility Function

How is Utility function "atol()" used in C++?
How to convert a string to Long Integer?

Explanation

atol() is a Utility Function that converts a string into a long value. The string must contain a valid long integer value, the rest of the string characters are terminated by white space, punctuation, characters. If a long integer is not found the result may be undefined, but in most scenarios will return 0.

Syntax to convert a string to Long Integer:


int atol(const char *str);

Example :



#include <stdlib.h>
#include <iostream.h>
int main()
{
char arr[10];
cout << "Enter a string with a long integer:: ";
cin >> arr;
cout << "Value returned by atol is:: " << atoi(arr) <<'\n';
cout << "Bytes occupied is:: " << sizeof(atoi(arr));
}

Result :

Enter a string with a long integer:: 134.56
The entered value is:: 134
The bytes occupied is:: 4

In the above example atol() is used to return the long value as "134" leaving the decimal ".56".

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