Section (3) strtoul
Name
strtoul, strtoull, strtouq — convert a string to an unsigned long integer
Synopsis
#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) ; |
![]() |
Note | |||
---|---|---|---|---|
|
DESCRIPTION
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 _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.)
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 _zsingle_quotesz_ _zsingle_quotesz_ but **endptr
is _zsingle_quotesz_ _zsingle_quotesz_ on return, the
entire string is valid.
The strtoull
() function
works just like the strtoul
()
function but returns an unsigned long long
int value.
RETURN 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 (nonnegated) 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
).
ERRORS
- 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).
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
Interface | Attribute | Value |
strtoul (), strtoull (), strtouq () |
Thread safety | MT-Safe locale |
CONFORMING TO
strtoul
(): POSIX.1-2001,
POSIX.1-2008, C89, C99 SVr4.
strtoull
(): POSIX.1-2001,
POSIX.1-2008, C99.
NOTES
Since strtoul
() can
legitimately return 0 or ULONG_MAX
(ULLONG_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 nonzero 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.
EXAMPLE
See the example on the strtol(3) manual page; the use of the functions described in this manual page is similar.
COLOPHON
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
https://www.kernel.org/doc/man−pages/.
Copyright 1993 David Metcalfe (davidprism.demon.co.uk) %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END References consulted: 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() |