strtoul(3) - Linux manual page (original) (raw)
strtoul(3) Library Functions Manual strtoul(3)
NAME top
strtoul, strtoull, strtouq - convert a string to an unsigned long
integerLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <stdlib.h>**
**unsigned long strtoul(const char *restrict** _nptr_**,**
**char _Nullable restrict** _endptr_**, int** _base_**);**
**unsigned long long strtoull(const char *restrict** _nptr_**,**
**char _Nullable restrict** _endptr_**, int** _base_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**strtoull**():
_ISOC99_SOURCE
|| /* glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCEDESCRIPTION top
The **strtoul**() function converts the initial part of the string in
_nptr_ to an _unsigned long_ 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)](../man3/isspace.3.html)) 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 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, and the _base_ is supported, **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_ value.RETURN VALUE top
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](../man3/errno.3.html)_ to **ERANGE**. Precisely
the same holds for **strtoull**() (with **ULLONG_MAX** instead of
**ULONG_MAX**).ERRORS top
This function does not modify _[errno](../man3/errno.3.html)_ on success.
**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](../man3/errno.3.html)_ to **EINVAL** in case no
conversion was performed (no digits seen, and 0 returned).ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌───────────────────────────────┬───────────────┬────────────────┐
│ **Interface** │ **Attribute** │ **Value** │
├───────────────────────────────┼───────────────┼────────────────┤
│ **strtoul**(), **strtoull**(), │ Thread safety │ MT-Safe locale │
│ **strtouq**() │ │ │
└───────────────────────────────┴───────────────┴────────────────┘VERSIONS top
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**().STANDARDS top
C11, POSIX.1-2008.HISTORY top
**strtoul**()
POSIX.1-2001, C89, SVr4.
**strtoull**()
POSIX.1-2001, C99.CAVEATS top
Since **strtoul**() can legitimately return 0 or **ULONG_MAX** (**ULLONG_MAX**
for **strtoull**()) on both success and failure, the calling program
should set _[errno](../man3/errno.3.html)_ to 0 before the call, and then determine if an
error occurred by checking whether _[errno](../man3/errno.3.html)_ has a nonzero value after
the call.
Negative values are considered valid input and are silently
converted to the equivalent _unsigned long_ value.EXAMPLES top
See the example on the [strtol(3)](../man3/strtol.3.html) manual page; the use of the
functions described in this manual page is similar.SEE ALSO top
[a64l(3)](../man3/a64l.3.html), [atof(3)](../man3/atof.3.html), [atoi(3)](../man3/atoi.3.html), [atol(3)](../man3/atol.3.html), [strtod(3)](../man3/strtod.3.html), [strtol(3)](../man3/strtol.3.html),
[strtoumax(3)](../man3/strtoumax.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 strtoul(3)
Pages that refer to this page:capsh(1), a64l(3), atof(3), atoi(3), sscanf(3), strtod(3), strtoimax(3), strtol(3), bpf-helpers(7), logrotate(8)