Header File 

stdlib.h  

Category 

Conversion Routines, Math Routines 

Prototype 

long atol(const char *s); 

long _wtol(const wchar_t *s); 

Description 

Converts a string to a long.

• atol converts the string pointed to by s to long. atol recognizes (in the following order)
• An optional string of tabs and spaces
• An optional sign
• A string of digits

[ws] [sn] [ddd] 

In this function, the first unrecognized character ends the conversion. There are no provisions for overflow in atol (results are undefined). 

Return Value 

atol returns the converted value of the input string. If the string cannot be converted to a number of the corresponding type (b), atol returns 0. 

Example  

 #include <stdlib.h>
 #include <stdio.h>
 int main(void)
 {
    long l;
    char *lstr = "98765432";
    l = atol(lstr);
    printf("string = %s integer = %ld\n", lstr, l);
    return(0);
 }

Portability