strtoul, strtoull

Defined in header `<stdlib.h>`
unsigned long strtoul( const char str, char *str_end, int base );		(until C99)
unsigned long strtoul( const char restrict str, char *restrict str_end, int base );		(since C99)
unsigned long long strtoull( const char restrict str, char *restrict str_end, int base );		(since C99)

Interprets an unsigned integer value in a byte string pointed to by str.

Function discards any whitespace characters (as identified by calling isspace()) until first non-whitespace character is found. Then it takes as many characters as possible to form a valid base-n (where n=base) unsigned integer number representation and converts them to an integer value. The valid unsigned integer value consists of the following parts:

(optional) prefix (0) indicating octal base (applies only when the base is 8 or 0)
(optional) prefix (0x or 0X) indicating hexadecimal base (applies only when the base is 16 or 0)
a sequence of digits

The set of valid digits for base-2 integer is 01, for base-3 integer is 012, and so on. For bases larger than 10, valid digits include alphabetic characters, starting from Aa for base-11 integer, to Zz for base-36 integer. The case of the characters is ignored.

Additional numeric formats may be accepted by the currently installed C locale.

If the value of base is 0, the numeric base is auto-detected: if the prefix is 0, the base is octal, if the prefix is 0x or 0X, the base is hexadecimal, otherwise the base is decimal.

The functions sets the pointer pointed to by str_end to point to the character past the last character interpreted. If str_end is NULL, it is ignored.

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
 
int main(void) 
{
    /* Decimal */
    printf("%lu\n", strtoul("",NULL,10));        /* empty string           */
    printf("%lu\n", strtoul(" +0123",NULL,10));  /* leading space and zero */
    printf("%lu\n", strtoul("123",NULL,0));
 
    /* Binary */
    printf("%lu\n", strtoul("1100", NULL,2));
 
    /* Octal */
    printf("%lu\n", strtoul("14",NULL,8));
    printf("%lu\n", strtoul("014",NULL,0));
 
    /* Base 13 */
    printf("%lu\n", strtoul("1c",NULL,13));
 
    /* Hexadecimal */
    printf("%lu\n", strtoul("FFFFFFFFFFFFFFFF",NULL,16));
    printf("%lu\n", strtoul("0xFFFFFFFFFFFFFFFF",NULL,0));
 
    /* Base 36 */
    printf("%lu\n", strtoul("XyZ",NULL,36));   /* 44027 */
 
    /* Overflow, a value too large for type unsigned long int. */
    errno = 0;
 
    printf("%lu\n", strtoul("18446744073709551616",NULL,10));           
    printf("%s\n",strerror(errno));   /* range error */
 
    /* Underflow. a value too small for type unsigned long int. */
    errno = 0;
    printf("%lu\n", strtoul("-1",NULL,10));
    printf("%s\n",strerror(errno));   /* success */
 
    /* Using str_end. */
    char *str_end;
    printf("%lu\n", strtoul("  00123 999",&str_end,10));
    printf("[%c]\n", *str_end);
    printf("%lu\n", strtoul(str_end,NULL,10)); 
 
    return 0;
}

Output:

0
123
123
12
12
12
25
18446744073709551615
18446744073709551615
44027
18446744073709551615
Numerical result out of range
18446744073709551615
Success
123
[ ]
999

[edit] See also

atoiatolatoll	converts a byte string to an integer value (function)
strtolstrtoll	converts a byte string to an integer value (function)
C++ documentation for strtoul

Language
Standard Library
Type support
Dynamic memory management
Error handling
Program utilities
Date and time utilities
Strings library
Algorithms
Numerics
Input/output support
Localization support
Thread support (C11)
Atomic operations (C11)

strtoul, strtoull

Contents

[edit] Parameters

[edit] Return value

[edit] Example

[edit] See also

str	-	pointer to the null-terminated byte string to be interpreted
str_end	-	pointer to a pointer to character.
base	-	base of the interpreted integer value