NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON
STRTOUL(3) Linux Programmer's Manual STRTOUL(3)
strtoul, strtoull, strtouq - convert a string to an unsigned long integer
#include <stdlib.h>
unsigned long int strtoul(const char *nptr, char **endptr, int base);
unsigned long long int strtoull(const char *nptr, char **endptr,
int base);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
strtoull(): XOPEN_SOURCE >= 600 || _BSD_SOURCE || _SVID_SOURCE ||
_ISOC99_SOURCE; or cc -std=c99
The strtoul() function converts the initial part of the string in nptr to an
unsigned long int value 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)) 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 int value in the
obvious manner, stopping at the first character which is not 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() stores the address of the first invalid
character in *endptr. If there were no digits at all, strtoul() stores the
original value of nptr in *endptr (and returns 0). In particular, if *nptr is
not '\0' but **endptr is '\0' on return, the entire string is valid.
The strtoull() function works just like the strtoul() function but returns an
unsigned long long int value.
The strtoul() function returns either the result of the conversion or, if
there was a leading minus sign, the negation of the result of the conversion
represented as an unsigned value, unless the original (non-negated) value
would overflow; in the latter case, strtoul() returns ULONG_MAX and sets errno
to ERANGE. Precisely the same holds for strtoull() (with ULLONG_MAX instead
of ULONG_MAX).
EINVAL (not in C99) The given base contains an unsupported value.
ERANGE The resulting value was out of range.
The implementation may also set errno to EINVAL in case no conversion was
performed (no digits seen, and 0 returned).
strtoul() conforms to SVr4, C89, C99 and POSIX-2001, and strtoull() to C99 and
POSIX.1-2001.
Since strtoul() can legitimately return 0 or LONG_MAX (LLONG_MAX for
strtoull()) on both success and failure, the calling program should set errno
to 0 before the call, and then determine if an error occurred by checking
whether errno has a non-zero value after the call.
In locales other than the "C" locale, other strings may be accepted. (For
example, the thousands separator of the current locale may be supported.)
BSD also has
u_quad_t strtouq(const char *nptr, char **endptr, int base);
with completely analogous definition. Depending on the wordsize of the
current architecture, this may be equivalent to strtoull() or to strtoul().
Negative values are considered valid input and are silently converted to the
equivalent unsigned long int value.
See the example on the strtol(3) manual page; the use of the functions
described in this manual page is similar.
atof(3), atoi(3), atol(3), strtod(3), strtol(3)
This page is part of release 3.23 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2007-07-26 STRTOUL(3)