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1.\" Copyright (c) 1990, 1991 The Regents of the University of California.
2.\" All rights reserved.
3.\"
4.\" This code is derived from software contributed to Berkeley by
5.\" Chris Torek and the American National Standards Committee X3,
6.\" on Information Processing Systems.
7.\"
8.\" Redistribution and use in source and binary forms, with or without
9.\" modification, are permitted provided that the following conditions
10.\" are met:
11.\" 1. Redistributions of source code must retain the above copyright
12.\" notice, this list of conditions and the following disclaimer.
13.\" 2. Redistributions in binary form must reproduce the above copyright
14.\" notice, this list of conditions and the following disclaimer in the
15.\" documentation and/or other materials provided with the distribution.
16.\" 3. Neither the name of the University nor the names of its contributors
17.\" may be used to endorse or promote products derived from this software
18.\" without specific prior written permission.
19.\"
20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30.\" SUCH DAMAGE.
31.\"
32.\" $OpenBSD: strtoul.3,v 1.19 2007/11/13 18:30:04 tobias Exp $
33.\"
34.Dd $Mdocdate: November 13 2007 $
35.Dt STRTOUL 3
36.Os
37.Sh NAME
38.Nm strtoul ,
39.Nm strtoull ,
40.Nm strtoumax ,
41.Nm strtouq
42.Nd "convert a string to an unsigned long, unsigned long long or uintmax_t integer"
43.Sh SYNOPSIS
44.Fd #include <limits.h>
45.Fd #include <stdlib.h>
46.Ft unsigned long
47.Fn strtoul "const char *nptr" "char **endptr" "int base"
48.Pp
49.Ft unsigned long long
50.Fn strtoull "const char *nptr" "char **endptr" "int base"
51.Pp
52.Fd #include <inttypes.h>
53.Ft uintmax_t
54.Fn strtoumax "const char *nptr" "char **endptr" "int base"
55.Pp
56.Fd #include <sys/types.h>
57.Fd #include <limits.h>
58.Fd #include <stdlib.h>
59.Ft u_quad_t
60.Fn strtouq "const char *nptr" "char **endptr" "int base"
61.Sh DESCRIPTION
62The
63.Fn strtoul
64function converts the string in
65.Fa nptr
66to an
67.Li unsigned long
68value.
69The
70.Fn strtoull
71function converts the string in
72.Fa nptr
73to an
74.Li unsigned long long
75value.
76The
77.Fn strtoumax
78function converts the string in
79.Fa nptr
80to a
81.Li umaxint_t
82value.
83The
84.Fn strtouq
85function is a deprecated equivalent of
86.Fn strtoull
87and is provided for backwards compatibility with legacy programs.
88The conversion is done according to the given
89.Fa base ,
90which must be a number between 2 and 36 inclusive
91or the special value 0.
92If the string in
93.Fa nptr
94represents a negative number, it will be converted to its unsigned equivalent.
95This behavior is consistent with what happens when a signed integer type is
96cast to its unsigned counterpart.
97.Pp
98The string may begin with an arbitrary amount of whitespace
99(as determined by
100.Xr isspace 3 )
101followed by a single optional
102.Ql +
103or
104.Ql -
105sign.
106If
107.Fa base
108is zero or 16, the string may then include a
109.Ql 0x
110prefix, and the number will be read in base 16; otherwise, a zero
111.Fa base
112is taken as 10 (decimal) unless the next character is
113.Ql 0 ,
114in which case it is taken as 8 (octal).
115.Pp
116The remainder of the string is converted to an
117.Li unsigned long
118value in the obvious manner, stopping at the end of the string
119or at the first character that does not produce a valid digit
120in the given base.
121(In bases above 10, the letter
122.Ql A
123in either upper or lower case represents 10,
124.Ql B
125represents 11, and so forth, with
126.Ql Z
127representing 35.)
128.Pp
129If
130.Fa endptr
131is non-null,
132.Fn strtoul
133stores the address of the first invalid character in
134.Fa *endptr .
135If there were no digits at all, however,
136.Fn strtoul
137stores the original value of
138.Fa nptr
139in
140.Fa *endptr .
141(Thus, if
142.Fa *nptr
143is not
144.Ql \e0
145but
146.Fa **endptr
147is
148.Ql \e0
149on return, the entire string was valid.)
150.Sh RETURN VALUES
151The
152.Fn strtoul ,
153.Fn strtoull ,
154.Fn strtoumax
155and
156.Fn strtouq
157functions return either the result of the conversion or,
158if there was a leading minus sign,
159the negation of the result of the conversion,
160unless the original (non-negated) value would overflow.
161If overflow occurs,
162.Fn strtoul
163returns
164.Dv ULONG_MAX ,
165.Fn strtoull
166returns
167.Dv ULLONG_MAX ,
168.Fn strtoumax
169returns
170.Dv UINTMAX_MAX ,
171.Fn strtouq
172returns
173.Dv ULLONG_MAX
174and the global variable
175.Va errno
176is set to
177.Er ERANGE .
178If no conversion could be performed, 0 is returned;
179the global variable
180.Va errno
181is also set to
182.Er EINVAL,
183though this is not portable across all platforms.
184.Pp
185There is no way to determine if
186.Fn strtoul
187has processed a negative number (and returned an unsigned value) short of
188examining the string in
189.Fa nptr
190directly.
191.Sh EXAMPLES
192Ensuring that a string is a valid number (i.e., in range and containing no
193trailing characters) requires clearing
194.Va errno
195beforehand explicitly since
196.Va errno
197is not changed on a successful call to
198.Fn strtoul ,
199and the return value of
200.Fn strtoul
201cannot be used unambiguously to signal an error:
202.Bd -literal -offset indent
203char *ep;
204unsigned long ulval;
205
206\&...
207
208errno = 0;
209ulval = strtoul(buf, &ep, 10);
210if (buf[0] == '\e0' || *ep != '\e0')
211 goto not_a_number;
212if (errno == ERANGE && ulval == ULONG_MAX)
213 goto out_of_range;
214.Ed
215.Pp
216This example will accept
217.Dq 12
218but not
219.Dq 12foo
220or
221.Dq 12\en .
222If trailing whitespace is acceptable, further checks must be done on
223.Va *ep ;
224alternately, use
225.Xr sscanf 3 .
226.Sh ERRORS
227.Bl -tag -width Er
228.It Bq Er ERANGE
229The given string was out of range; the value converted has been clamped.
230.El
231.Sh SEE ALSO
232.Xr sscanf 3 ,
233.Xr strtol 3
234.Sh STANDARDS
235The
236.Fn strtoul ,
237.Fn strtoull ,
238and
239.Fn strtoumax
240functions conform to
241.St -ansiC-99 .
242The
243.Fn strtouq
244function is a
245.Bx
246extension and is provided for backwards compatibility with legacy programs.
247.Sh BUGS
248Ignores the current locale.