In this tutorial, you will learn about C strtol() – a string conversion function that converts a sequence of character representing an integer into long int.

We have to include stdlib.h header file before using this function.

#include<stdlib.h>

Function prototype of C strtol()

---

long strtol( const char *sPtr, char **endPtr, int base );

where,

sPtr = string representing an integer number

endPtr = pointer set by the function to the next character in sPtr after integer value

base = base of the value being converted which can be specified as 0 or any value between 2 and 36

Return Type of C strtol()

---

This function returns 0 if it is unable to convert any portion of sPtr to a long int.

Note: Any whitespace characters at the beginning of the string are ignored.

C program to illustrate the concept of strtol()

//C string conversion function strtol

#include<stdio.h>
#include<stdlib.h>

int main()
{
   //initializing string pointer
   const char *sPtr = "423 student are pass";

   long n; //variable to store converted sequence
   char *endPtr; //char type pointer

   n = strtol( sPtr, &endPtr, 0 );

   printf("Original String: \"%s\"\n", sPtr);
   printf("\nLong int Value: %ld"
          "\nRemaining string part: %s\n", n, endPtr);

   return 0;
}

Output

Explanation

In the above example, the long int value converted from the string is stored in n whereas, the remaining part of the string is assigned to endPtr.

The base value 0 indicates that the converted value can be in the following format:

octal format = base 8

decimal format = base 10

hexadecimal format = base 16