STRTOUL(3)

NAME
strtoul, strtoul_l, strtoull, strtoull_l, strtoumax, strtoumax_l, strtouq - convert a string to an unsigned long, unsigned long long, uintmax_t, or u_quad_t integer

LIBRARY
libc

SYNOPSIS
#include <stdlib.h>
#include <limits.h>
unsigned long
strtoul(const char * restrict nptr, char ** restrict endptr, int base);
unsigned long long
strtoull(const char * restrict nptr, char ** restrict endptr, int base);
#include <inttypes.h>
uintmax_t
strtoumax(const char * restrict nptr, char ** restrict endptr, int base);
#include <sys/types.h>
u_quad_t
strtouq(const char *nptr, char **endptr, int base);
#include <xlocale.h>
unsigned long
strtoul_l(const char * restrict nptr, char ** restrict endptr, int base, locale_t locale);
unsigned long long
strtoull_l(const char * restrict nptr, char ** restrict endptr, int base, locale_t locale);
uintmax_t
strtoumax_l(const char * restrict nptr, char ** restrict endptr, int base, locale_t locale);

DESCRIPTION
The strtoul() and strtoul_l() functions convert the string in nptr to an unsigned long value. The strtoull() and strtoull_l() functions convert the string in nptr to an unsigned long long value. The strtoumax() and strtoumax_l() functions convert the string in nptr to an uintmax_t value. The strtouq() function converts the string in nptr to a u_quad_t value. The conversion is done according to the given base, which must be between 2 and 36 inclusive, or be the special value 0.

The string may begin with an arbitrary amount of white space (as determined by isspace(3) or isspace_l(3)) followed by a single optional ‘+’ or ‘-’ sign. If base is zero or 16, the string may then include a “0x” prefix, and the number will be read in base 16; otherwise, a zero base is taken as 10 (decimal) unless the next character is ‘0’, in which case it is taken as 8 (octal).

The remainder of the string is converted to an unsigned long value in the obvious manner, stopping at the end of the string or at the first character that does not produce a valid digit in the given base. (In bases above 10, the letter ‘A’ in either upper or lower case represents 10, ‘B’ represents 11, and so forth, with ‘Z’ representing 35.)

If endptr is not NULL, strtoul() and strtoul_l() store the address of the first invalid character in *endptr. If there were no digits at all, however, strtoul() and strtoul_l() store the original value of nptr in *endptr. (Thus, if *nptr is not ‘\0’ but **endptr is ‘\0’ on return, the entire string was valid.)

The strtoul_l(), strtoull_l(), and strtoumax_l() functions take an explicit locale argument, whereas the strtoul(), strtoull(), strtoumax(), and strtouq() functions use the current global or per-thread locale.

RETURN VALUES
The strtoul(), strtoul_l(), strtoull(), strtoull_l(), strtoumax(), strtoumax_l(), and strtouq() functions return either the result of the conversion or, if there was a leading minus sign, the negation of the result of the conversion, unless the original (non-negated) value would overflow; in the latter case, strtoul() and strtoul_l() return ULONG_MAX, strtoull() and strtoull_l() return ULLONG_MAX, strtoumax() and strtoumax_l() return UINTMAX_MAX, and strtouq() returns ULLONG_MAX. In all cases, errno is set to ERANGE. If no conversion could be performed, 0 is returned and the global variable errno is set to EINVAL (the last feature is not portable across all platforms).

ERRORS

[EINVAL]
    The value of base is not supported or no conversion could be performed (the last feature is not portable across all platforms).

[ERANGE]
    The given string was out of range; the value converted has been clamped.

SEE ALSO
strtol(3), strtonum(3), wcstoul(3), xlocale(3)

STANDARDS
The strtoul() function conforms to isoC. The strtoull() and strtoumax() functions conform to isoC-99. The BSD strtouq() function is deprecated.