strtoimax

intmax_t strtoimax( const char *restrict nptr, 
                    char **restrict endptr, int base );

uintmax_t strtoumax( const char *restrict nptr, 
                     char **restrict endptr, int base );

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

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

• (optional) plus or minus sign
• (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.

If the minus sign was part of the input sequence, the numeric value calculated from the sequence of digits is negated in the result type.

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

If the nptr is empty or does not have the expected form, no conversion is performed, and (if enptr is not NULL) the value of nptr is stored in the object pointed to by endptr.

Parameters

Return value

• If successful, an integer value corresponding to the contents of str is returned.
• If the converted value falls out of range of corresponding return type, a range error occurs (setting [[cpp/error/errno|errno]] to ERANGE) and INTMAX_MAX, INTMAX_MIN, UINTMAX_MAX or ​0​ is returned, as appropriate.
• If no conversion can be performed, ​0​ is returned.

Example

#include <stdio.h>
#include <inttypes.h>
#include <errno.h>
#include <string.h>
 
int main(void)
{
 
    char* endptr;
 
    printf("%ld\n", strtoimax(" -123junk",&endptr,10)); /* base 10                    */
    printf("%ld\n", strtoimax("11111111",&endptr,2));   /* base 2                     */
    printf("%ld\n", strtoimax("XyZ",&endptr,36));       /* base 36                    */
    printf("%ld\n", strtoimax("010",&endptr,0));        /* octal auto-detection       */
    printf("%ld\n", strtoimax("10",&endptr,0));         /* decimal auto-detection     */
    printf("%ld\n", strtoimax("0x10",&endptr,0));       /* hexadecimal auto-detection */
 
    /* range error             */
    /* LONG_MAX+1 --> LONG_MAX */
    errno = 0;
    printf("%ld\n", strtoimax("9223372036854775808",&endptr,10));
    printf("%s\n", strerror(errno));
 
    return 0;
}

-123
255
44027
8
10
16
9223372036854775807
Numerical result out of range

References

• C11 standard (ISO/IEC 9899:2011):
  • 7.8.2.3 The strtoimax and strtoumax functions (p: 219)
• C99 standard (ISO/IEC 9899:1999):
  • 7.8.2.3 The strtoimax and strtoumax functions (p: 200)

See also