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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | 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():
_ISOC99_SOURCE ||
|| /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
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 uppercase or lowercase 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
(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).
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).
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────┬───────────────┬────────────────┐
│Interface │ Attribute │ Value │
├─────────────────────────────────┼───────────────┼────────────────┤
│strtoul(), strtoull(), strtouq() │ Thread safety │ MT-Safe locale │
└─────────────────────────────────┴───────────────┴────────────────┘
strtoul(): POSIX.1-2001, POSIX.1-2008, C89, C99 SVr4.
strtoull(): POSIX.1-2001, POSIX.1-2008, C99.
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.
See the example on the strtol(3) manual page; the use of the
functions described in this manual page is similar.
a64l(3), atof(3), atoi(3), atol(3), strtod(3), strtol(3)
This page is part of release 4.12 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/.
GNU 2016-07-17 STRTOUL(3)
Pages that refer to this page: a64l(3), atof(3), atoi(3), scanf(3), strtod(3), strtoimax(3), strtol(3), logrotate(8)