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strtoul.3p (6707B)

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.TH STRTOUL "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
strtoul,
strtoull
\(em convert a string to an unsigned long
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>
.P
unsigned long strtoul(const char *restrict \fIstr\fP,
    char **restrict \fIendptr\fP, int \fIbase\fP);
unsigned long long strtoull(const char *restrict \fIstr\fP,
    char **restrict \fIendptr\fP, int \fIbase\fP);
.fi
.SH DESCRIPTION
The functionality described on this reference page is aligned with the
ISO\ C standard. Any conflict between the requirements described here and the
ISO\ C standard is unintentional. This volume of POSIX.1\(hy2017 defers to the ISO\ C standard.
.P
These functions shall convert the initial portion of the string pointed
to by
.IR str
to a type
.BR "unsigned long"
and
.BR "unsigned long long"
representation, respectively. First, they decompose the input string
into three parts:
.IP " 1." 4
An initial, possibly empty, sequence of white-space characters (as
specified by
\fIisspace\fR())
.IP " 2." 4
A subject sequence interpreted as an integer represented in some radix
determined by the value of
.IR base
.IP " 3." 4
A final string of one or more unrecognized characters, including
the terminating NUL character of the input string
.P
Then they shall attempt to convert the subject sequence to an
unsigned integer, and return the result.
.P
If the value of
.IR base
is 0, the expected form of the subject sequence is that of a decimal
constant, octal constant, or hexadecimal constant, any of which may be
preceded by a
.BR '+' 
or
.BR '\-' 
sign. A decimal constant begins with a non-zero digit, and consists of
a sequence of decimal digits. An octal constant consists of the prefix
.BR '0' 
optionally followed by a sequence of the digits
.BR '0' 
to
.BR '7' 
only. A hexadecimal constant consists of the prefix 0x or 0X followed
by a sequence of the decimal digits and letters
.BR 'a' 
(or
.BR 'A' )
to
.BR 'f' 
(or
.BR 'F' )
with values 10 to 15 respectively.
.P
If the value of
.IR base
is between 2 and 36, the expected form of the subject sequence is a
sequence of letters and digits representing an integer with the radix
specified by
.IR base ,
optionally preceded by a
.BR '+' 
or
.BR '\-' 
sign. The letters from
.BR 'a' 
(or
.BR 'A' )
to
.BR 'z' 
(or
.BR 'Z' )
inclusive are ascribed the values 10 to 35; only letters whose ascribed
values are less than that of
.IR base
are permitted. If the value of
.IR base
is 16, the characters 0x or 0X may optionally precede the sequence of
letters and digits, following the sign if present.
.P
The subject sequence is defined as the longest initial subsequence of
the input string, starting with the first non-white-space character
that is of the expected form. The subject sequence shall contain no
characters if the input string is empty or consists entirely of
white-space characters, or if the first non-white-space character is
other than a sign or a permissible letter or digit.
.P
If the subject sequence has the expected form and the value of
.IR base
is 0, the sequence of characters starting with the first digit shall be
interpreted as an integer constant. If the subject sequence has the
expected form and the value of
.IR base
is between 2 and 36, it shall be used as the base for conversion,
ascribing to each letter its value as given above. If the subject
sequence begins with a
<hyphen-minus>,
the value resulting from the
conversion shall be negated. A pointer to the final string shall be
stored in the object pointed to by
.IR endptr ,
provided that
.IR endptr
is not a null pointer.
.P
In other than the C
or POSIX
locale, additional locale-specific subject sequence forms may be
accepted.
.P
If the subject sequence is empty or does not have the expected form, no
conversion shall be performed; the value of
.IR str
shall be stored in the object pointed to by
.IR endptr ,
provided that
.IR endptr
is not a null pointer.
.P
These functions shall not change the setting of
.IR errno
if successful.
.P
Since 0,
{ULONG_MAX},
and
{ULLONG_MAX}
are returned on error and are also valid returns on success, an
application wishing to check for error situations should set
.IR errno
to 0, then call
\fIstrtoul\fR()
or
\fIstrtoull\fR(),
then check
.IR errno .
.SH "RETURN VALUE"
Upon successful completion, these functions shall return the converted
value, if any. If no conversion could be performed, 0 shall be returned
and
.IR errno
may be set to
.BR [EINVAL] .
.P
If the value of
.IR base
is not supported, 0 shall be returned and
.IR errno
shall be set to
.BR [EINVAL] .
.P
If the correct value is outside the range of representable values,
{ULONG_MAX}
or
{ULLONG_MAX}
shall be returned and
.IR errno
set to
.BR [ERANGE] .
.SH ERRORS
These functions shall fail if:
.TP
.BR EINVAL
The value of
.IR base
is not supported.
.TP
.BR ERANGE
The value to be returned is not representable.
.P
These functions may fail if:
.TP
.BR EINVAL
No conversion could be performed.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
Since the value of
.IR *endptr
is unspecified if the value of
.IR base
is not supported, applications should either ensure that
.IR base
has a supported value (0 or between 2 and 36) before the call, or check
for an
.BR [EINVAL] 
error before examining
.IR *endptr .
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIfscanf\fR\^(\|)",
.IR "\fIisalpha\fR\^(\|)",
.IR "\fIstrtod\fR\^(\|)",
.IR "\fIstrtol\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<stdlib.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .