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\"     from: @(#)strtoul.3      8.1 (Berkeley) 6/4/93
\"
Dd November 13, 2015
Dt STRTOUL 3
Os
Sh NAME
Nm strtoul ,
Nm strtoull ,
Nm strtoumax ,
Nm strtouq
Nd convert a string to an unsigned long, unsigned long long, uintmax_t or u_quad_t integer
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In stdlib.h
In limits.h
Ft unsigned long int
Fn strtoul "const char * restrict nptr" "char ** restrict endptr" "int base"
Ft unsigned long long int
Fn strtoull "const char * restrict nptr" "char ** restrict endptr" "int base"
Pp
In inttypes.h
Ft uintmax_t
Fn strtoumax "const char * restrict nptr" "char ** restrict endptr" "int base"
Pp
In sys/types.h
In stdlib.h
In limits.h
Ft u_quad_t
Fn strtouq "const char * restrict nptr" "char ** restrict endptr" "int base"
Sh DESCRIPTION
The
Fn strtoul
function
converts the string in
Fa nptr
to an
Ft unsigned long int
value.
The
Fn strtoull
function
converts the string in
Fa nptr
to an
Ft unsigned long long int
value.
The
Fn strtoumax
function
converts the string in
Fa nptr
to an
Ft uintmax_t
value.
The
Fn strtouq
function
converts the string in
Fa nptr
to a
Ft u_quad_t
value.
Pp
The conversion is done according to the given
Fa base ,
which must be between 2 and 36 inclusive,
or be the special value 0.
Pp
The string may begin with an arbitrary amount of white space
(as determined by
Xr isspace 3 )
followed by a single optional
Ql +
or
Ql -
sign.
If
Fa base
is zero or 16,
the string may then include a
Ql 0x
or
Ql 0X
prefix,
and the number will be read in base 16; otherwise,
\" if the
\" .Fa base
\" is zero or 2,
\" the string may then include a
\" .Ql 0b
\" or
\" .Ql 0B
\" prefix,
\" and the number will be read in base 2; otherwise,
a zero
Fa base
is taken as 10 (decimal) unless the next character is
Ql 0 ,
in which case it is taken as 8 (octal).
Pp
The remainder of the string is converted to an appropriate
value in the obvious manner,
stopping at the end of the string
or at the first character that does not produce a valid digit
in the given base.
(In bases above 10, the letter
Ql A
in either upper or lower case
represents 10,
Ql B
represents 11, and so forth, with
Ql Z
representing 35.)
Pp
If
Fa endptr
is non-nil, the functions store the address of the first invalid character in
Fa *endptr .
If there were no digits at all, however,
the functions store the original value of
Fa nptr
in
Fa *endptr .
(Thus, if
Fa *nptr
is not
Ql \e0
but
Fa **endptr
is
Ql \e0
on return, the entire string was valid.)
Sh RETURN VALUES
The
Fn 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,
unless the original (non-negated) value would overflow;
in the latter case,
Fn strtoul
returns
Dv ULONG_MAX ,
Fn strtoull
returns
Dv ULLONG_MAX ,
Fn strtoumax
returns
Dv UINTMAX_MAX ,
Fn strtouq
returns
Dv UQUAD_MAX ,
and the global variable
Va errno
is set to
Er ERANGE .
Pp
There is no way to determine if
Fn strtoul
has processed a negative number (and returned an unsigned value) short of
examining the string in
Fa nptr
directly.
If the
Fa base
argument is not supported then
Va errno
is set to
Er EINVAL
and the functions return 0.
Pp
If no error occurs,
Va errno
is left unchanged.
This behavior (which is unlike most library functions) is guaranteed
by the pertinent standards.
Sh EXAMPLES
Because the return value of
Fn strtoul
cannot be used unambiguously to detect an error,
Va errno
is left unchanged after a successful call.
To ensure that a string is a valid number (i.e., in range and containing no
trailing characters), clear
Va errno
beforehand explicitly, then check it afterwards:
Bd -literal -offset indent
char *ep;
unsigned long ulval;

\&...

errno = 0;
ulval = strtoul(buf, &ep, 10);
if (ep == buf)
       goto not_a_number;
if (*ep != '\e0')
       goto trailing_garbage;
if (errno) {
       assert(errno == ERANGE);
       assert(ulval == ULONG_MAX);
       goto out_of_range;
}
Ed
Pp
This example will accept
Dq 12
but not
Dq 12foo
or
Dq 12\en .
If trailing whitespace is acceptable, further checks must be done on
Va *ep ;
alternately, use
Xr sscanf 3 .
Sh ERRORS
Bl -tag -width Er
It Bq Er EINVAL
The
Ar base
is not between 2 and 36 and does not contain the special value 0.
It Bq Er ERANGE
The given string was out of range; the value converted has been clamped.
El
Sh SEE ALSO
Xr atof 3 ,
Xr atoi 3 ,
Xr atol 3 ,
Xr atoll 3 ,
Xr strtod 3 ,
Xr strtoi 3 ,
Xr strtoimax 3 ,
Xr strtol 3 ,
Xr strtoll 3 ,
Xr strtou 3
Sh STANDARDS
The
Fn strtoul
function
conforms to
St -ansiC .
The
Fn strtoull
and
Fn strtoumax
functions conform to
St -isoC-99 .
Pp
The
Fn strtouq
function is a
Bx
legacy function equivalent to
Fn strtoull
and should not be used in a new code.
Sh BUGS
Ignores the current locale.

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