Section (3) strtoul
strtoul, strtoull, strtouq — convert a string to an unsigned long integer
||const char *nptr,|
||const char *nptr,|
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 _zsingle_quotesz_+_zsingle_quotesz_ or _zsingle_quotesz_−_zsingle_quotesz_ 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 _zsingle_quotesz_0_zsingle_quotesz_, 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 _zsingle_quotesz_A_zsingle_quotesz_ in either uppercase or lowercase represents 10, _zsingle_quotesz_B_zsingle_quotesz_ represents 11, and so forth, with _zsingle_quotesz_Z_zsingle_quotesz_ representing 35.)
endptr is not
strtoul() stores the
address of the first invalid character in *
endptr. If there were no digits
strtoul() stores the
original value of
nptr in *
endptr (and returns 0). In
particular, if *
is not _zsingle_quotesz_ _zsingle_quotesz_ but **
endptr is _zsingle_quotesz_ _zsingle_quotesz_ on return, the
entire string is valid.
works just like the
function but returns an unsigned long long
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 (nonnegated) value would overflow; in the latter
ULONG_MAX and sets
errno to ERANGE. Precisely the same holds for
ULLONG_MAX instead of
(not in C99) The given
basecontains an unsupported value.
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).
For an explanation of the terms used in this section, see attributes(7).
||Thread safety||MT-Safe locale|
POSIX.1-2008, C89, C99 SVr4.
legitimately return 0 or
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 nonzero value after
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
const char *nptr,
with completely analogous definition. Depending on the
wordsize of the current architecture, this may be equivalent
strtoull() or to
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.
This page is part of release 5.04 of the Linux
man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
Copyright 1993 David Metcalfe (davidprism.demon.co.uk)
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Since the Linux kernel and libraries are constantly changing, this
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Linux libc source code
Lewine_zsingle_quotesz_s _POSIX Programmer_zsingle_quotesz_s Guide_ (O_zsingle_quotesz_Reilly & Associates, 1991)
386BSD man pages
Modified Sun Jul 25 10:54:03 1993 by Rik Faith (faithcs.unc.edu)
Fixed typo, aeb, 950823
2002-02-22, joey, mihtjel: Added strtoull()