atol


function
<cstdlib>
long int atol ( const char * str );

Convert string to long integer

Parses the C string str interpreting its content as an integral number, which is returned as a long int value.

The function first discards as many whitespace characters as necessary until the first non-whitespace character is found. Then, starting from this character, takes an optional initial plus or minus sign followed by as many numerical digits as possible, and interprets them as a numerical value.

The string can contain additional characters after those that form the integral number, which are ignored and have no effect on the behavior of this function.

If the first sequence of non-whitespace characters in str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed.

Parameters

str
C string containing the representation of an integral number.


Return Value

On success, the function returns the converted integral number as a long int value.
If no valid conversion could be performed, a zero value is returned.
If the correct value is out of the range of representable values, LONG_MAX or LONG_MIN is returned.

Example

1
2
3
4
5
6
7
8
9
10
11
12
13
14
/* atol example */
#include <stdio.h>
#include <stdlib.h>

int main ()
{
  long int li;
  char szInput [256];
  printf ("Enter a long number: ");
  gets ( szInput );
  li = atol (szInput);
  printf ("The value entered is %d. The double is %d.\n",li,li*2);
  return 0;
}


Output:

Enter a number: 567283
The value entered is 567283. The double is 1134566.


See also