strtol

Converts a string to a long value.

Defined in header <stdlib.h>

Syntax

#include <stdlib.h>
long strtoUconst char *s, char **endptr, intradix);

Portability

Remarks

strtol converts a character string, s, to a long integer value, s is a sequence of characters that can be interpreted as a long value; the characters must match this generic format:

where

[ws] = optional whitespace [sn] = optional sign (+ or -) [0] = optional zero (0) [x] = optional x or X [ddd] = optional digits

strtol stops reading the string at the first character it doesn't recognize.

If radix is between 2 and 36, the long integer is expressed in base radix. If radix is 0, the first few characters of s determine the base of the value being converted.

If radix is 1, it is considered to be an invalid value. If radix is less than 0 or greater than 36, it is considered to be an invalid value.

Any invalid value for radix causes the result to be 0 and sets the next character pointer *endiptr to the starting string pointer.

If the value in s is meant to be interpreted as octal, any character other than 0 to 7 will be unrecognized.

If the value in s is meant to be interpreted as decimal, any character other than 0 to 9 will be unrecognized.

If the value in s is meant to be interpreted as a number in any other base, then only the numerals and letters used to represent numbers in that base will be recognized. (For example, if radix equals 5, only 0 to 4 will be recognized; if radix equals 20, only 0 to 9 and A to / will be recognized.)

If endptr is not null, strtol sets ^endptr to point to the character that stopped the scan {^endptr = &iStopper).

Return value

strtol returns the value of the converted string, or 0 on error.

See also

• atol
• atol
• strtoul

Example

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

int main(void)
{
   char *string = "87654321", *endptr;
   long 1number;
   /* strtol converts string to long integer */
   Inumber = strtol(string, &endptr, 10);
   printf("string = %s  long = %ld\n", string, Inumber);
   return 0;

Differences from modern implementations

Nothing recorded yet.

Modern references

• cppreference (search)
• Microsoft C runtime (search)

These are search links, not yet checked by hand.

Stable link: /3.1/stdlib.h/strtol/ · short form /3.1/strtol/