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1 .\" $NetBSD: strtou.3,v 1.3 2015/07/11 15:51:33 wiz Exp $
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34 .\" from: @(#)strtoul.3 8.1 (Berkeley) 6/4/93
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36 .\" Created by Kamil Rytarowski, based on ID:
37 .\" NetBSD: strtoul.3,v 1.29 2015/03/10 13:00:58 christos Exp
38 .\"
39 .Dd April 30, 2015
40 .Dt STRTOU 3
41 .Os
42 .Sh NAME
43 .Nm strtou
44 .Nd convert a string to an uintmax_t integer
45 .Sh LIBRARY
46 .Lb libc
47 .Sh SYNOPSIS
48 .In inttypes.h
49 .Ft uintmax_t
50 .Fo strtou
51 .Fa "const char * restrict nptr"
52 .Fa "char ** restrict endptr"
53 .Fa "int base"
54 .Fa "uintmax_t lo"
55 .Fa "uintmax_t hi"
56 .Fa "int *rstatus"
57 .Fc
58 .Sh DESCRIPTION
59 The
60 .Fn strtou
61 function converts the string in
62 .Fa nptr
63 to an
64 .Ft uintmax_t
65 value.
66 The
67 .Fn strtou
68 function uses internally
69 .Xr strtoumax 3
70 and ensures that the result is always in the range [
71 .Fa lo ..
72 .Fa hi
73 ].
74 In adddition it always places
75 .Dv 0
76 on success or a conversion status in the
77 .Fa rstatus
78 argument, avoiding the
79 .Dv errno
80 gymnastics the other functions require.
81 The
82 .Fa rstatus
83 argument can be
84 .Dv NULL
85 if conversion status is to be ignored.
86 .Pp
87 The string may begin with an arbitrary amount of white space
88 (as determined by
89 .Xr isspace 3 )
90 followed by a single optional
91 .Ql +
92 or
93 .Ql -
94 sign.
95 If
96 .Fa base
97 is zero or 16,
98 the string may then include a
99 .Ql 0x
100 prefix,
101 and the number will be read in base 16; otherwise, a zero
102 .Fa base
103 is taken as 10 (decimal) unless the next character is
104 .Ql 0 ,
105 in which case it is taken as 8 (octal).
106 .Pp
107 The remainder of the string is converted to an
108 .Em uintmax_t
109 value in the obvious manner,
110 stopping at the end of the string
111 or at the first character that does not produce a valid digit
112 in the given base.
113 (In bases above 10, the letter
114 .Ql A
115 in either upper or lower case
116 represents 10,
117 .Ql B
118 represents 11, and so forth, with
119 .Ql Z
120 representing 35.)
121 .Pp
122 If
123 .Fa endptr
124 is non-nil,
125 .Fn strtou
126 stores the address of the first invalid character in
127 .Fa *endptr .
128 If there were no digits at all, however,
129 .Fn strtou
130 stores the original value of
131 .Fa nptr
132 in
133 .Fa *endptr .
134 (Thus, if
135 .Fa *nptr
136 is not
137 .Ql \e0
138 but
139 .Fa **endptr
140 is
141 .Ql \e0
142 on return, the entire string was valid.)
143 .Sh RETURN VALUES
144 The
145 .Fn strtou
146 function
147 always returns the closest value in the range specified by
148 the
149 .Fa lo
150 and
151 .Fa hi
152 arguments.
153 .Pp
154 The
155 .Va errno
156 value is guaranteed to be left unchanged.
157 .Pp
158 Errors are stored as the conversion status in the
159 .Fa rstatus
160 argument.
161 .Sh EXAMPLES
162 The following example will always return a number in
163 .Dv [1..99]
164 range no matter what the input is, and warn if the conversion failed.
165 .Bd -literal -offset indent
166 int e;
167 uintmax_t lval = strtou(buf, NULL, 0, 1, 99, &e);
168 if (e)
169 warnc(e, "conversion of `%s' to a number failed, using %ju",
170 buf, lval);
171 .Ed
172 .Sh ERRORS
173 .Bl -tag -width Er
174 .It Bq Er ECANCELED
175 The string did not contain any characters that were converted.
176 .It Bq Er EINVAL
177 The
178 .Ar base
179 is not between 2 and 36 and does not contain the special value 0.
180 .It Bq Er ENOTSUP
181 The string contained non-numeric characters that did not get converted.
182 In this case,
183 .Fa endptr
184 points to the first unconverted character.
185 .It Bq Er ERANGE
186 The given string was out of range; the value converted has been clamped; or
187 the range given was invalid, i.e.
188 .Fa lo
189 \*[Gt]
190 .Fa hi .
191 .El
192 .Sh SEE ALSO
193 .Xr atof 3 ,
194 .Xr atoi 3 ,
195 .Xr atol 3 ,
196 .Xr atoll 3 ,
197 .Xr strtod 3 ,
198 .Xr strtoi 3 ,
199 .Xr strtoimax 3 ,
200 .Xr strtol 3 ,
201 .Xr strtoll 3 ,
202 .Xr strtoul 3 ,
203 .Xr strtoull 3 ,
204 .Xr strtoumax 3
205 .Sh STANDARDS
206 The
207 .Fn strtou
208 function is a
209 .Nx
210 extension.
211 .Sh HISTORY
212 The
213 .Fn strtou
214 function first appeared in
215 .Nx 7 .
216 .Ox
217 introduced the
218 .Fn strtonum 3
219 function for the same purpose, but the interface makes it impossible to
220 properly differentiate illegal returns.
221 .Sh BUGS
222 Ignores the current locale.