27 .\" The contents of this file are subject to the terms of the
28 .\" Common Development and Distribution License (the "License").
29 .\" You may not use this file except in compliance with the License.
30 .\"
31 .\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
32 .\" or http://www.opensolaris.org/os/licensing.
33 .\" See the License for the specific language governing permissions
34 .\" and limitations under the License.
35 .\"
36 .\" When distributing Covered Code, include this CDDL HEADER in each
37 .\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
38 .\" If applicable, add the following below this CDDL HEADER, with the
39 .\" fields enclosed by brackets "[]" replaced with your own identifying
40 .\" information: Portions Copyright [yyyy] [name of copyright owner]
41 .\"
42 .\"
43 .\" Copyright 1989 AT&T
44 .\" Copyright (c) 1992, X/Open Company Limited. All Rights Reserved.
45 .\" Portions Copyright (c) 2006, Sun Microsystems, Inc. All Rights Reserved.
46 .\"
47 .TH STRTOD 3C "Nov 1, 2003"
48 .SH NAME
49 strtod, strtof, strtold, atof \- convert string to floating-point number
50 .SH SYNOPSIS
51 .LP
52 .nf
53 #include <stdlib.h>
54
55 \fBdouble\fR \fBstrtod\fR(\fBconst char *restrict\fR \fInptr\fR, \fBchar **restrict\fR \fIendptr\fR);
56 .fi
57
58 .LP
59 .nf
60 \fBfloat\fR \fBstrtof\fR(\fBconst char *restrict\fR \fInptr\fR, \fBchar **restrict\fR \fIendptr\fR);
61 .fi
62
63 .LP
64 .nf
65 \fBlong double\fR \fBstrtold\fR(\fBconst char *restrict\fR \fInptr\fR, \fBchar **restrict\fR \fIendptr\fR);
66 .fi
67
68 .LP
69 .nf
70 \fBdouble\fR \fBatof\fR(\fBconst char *\fR\fIstr\fR);
71 .fi
72
73 .SH DESCRIPTION
74 .sp
75 .LP
76 The \fBstrtod()\fR, \fBstrtof()\fR, and \fBstrtold()\fR functions convert the
77 initial portion of the string pointed to by \fInptr\fR to \fBdouble\fR,
78 \fBfloat\fR, and \fBlong double\fR representation, respectively. First they
79 decompose the input string into three parts:
80 .RS +4
81 .TP
82 1.
83 An initial, possibly empty, sequence of white-space characters (as specified
84 by \fBisspace\fR(3C))
85 .RE
86 .RS +4
87 .TP
88 2.
89 A subject sequence interpreted as a floating-point constant or representing
90 infinity or NaN
91 .RE
92 .RS +4
93 .TP
94 3.
95 A final string of one or more unrecognized characters, including the
132 .sp
133 .in +2
134 .nf
135 n-char-sequence:
136 digit
137 nondigit
138 n-char-sequence digit
139 n-char-sequence nondigit
140 .fi
141 .in -2
142
143 .RE
144 .sp
145 .LP
146 In default mode for \fBstrtod()\fR, only decimal, INF/INFINITY, and
147 NAN/NAN(\fIn-char-sequence\fR) forms are recognized. In C99/SUSv3 mode,
148 hexadecimal strings are also recognized.
149 .sp
150 .LP
151 In default mode for \fBstrtod()\fR, the \fIn-char-sequence\fR in the
152 NAN(\fIn-char-equence\fR) form can contain any character except ')' (right
153 parenthesis) or '\e0' (null). In C99/SUSv3 mode, the \fIn-char-sequence\fR can
154 contain only upper and lower case letters, digits, and '_' (underscore).
155 .sp
156 .LP
157 The \fBstrtof()\fR and \fBstrtold()\fR functions always function in
158 C99/SUSv3-conformant mode.
159 .sp
160 .LP
161 The subject sequence is defined as the longest initial subsequence of the input
162 string, starting with the first non-white-space character, that is of the
163 expected form. The subject sequence contains no characters if the input string
164 is not of the expected form.
165 .sp
166 .LP
167 If the subject sequence has the expected form for a floating-point number, the
168 sequence of characters starting with the first digit or the decimal-point
169 character (whichever occurs first) is interpreted as a floating constant of the
170 C language, except that the radix character is used in place of a period, and
171 that if neither an exponent part nor a radix character appears in a decimal
172 floating-point number, or if a binary exponent part does not appear in a
185 point inexact, underflow, or overflow exceptions as appropriate.
186 .sp
187 .LP
188 The radix character is defined in the program's locale (category
189 \fBLC_NUMERIC\fR). In the POSIX locale, or in a locale where the radix
190 character is not defined, the radix character defaults to a period ('.').
191 .sp
192 .LP
193 If the subject sequence is empty or does not have the expected form, no
194 conversion is performed; the value of \fInptr\fR is stored in the object
195 pointed to by \fIendptr\fR, provided that \fIendptr\fR is not a null pointer.
196 .sp
197 .LP
198 The \fBstrtod()\fR function does not change the setting of \fBerrno\fR if
199 successful.
200 .sp
201 .LP
202 The \fBatof(\fR\fIstr\fR\fB)\fR function call is equivalent to
203 \fBstrtod(\fR\fInptr\fR\fB, (char **)NULL)\fR.
204 .SH RETURN VALUES
205 .sp
206 .LP
207 Upon successful completion, these functions return the converted value. If no
208 conversion could be performed, \fB0\fR is returned.
209 .sp
210 .LP
211 If the correct value is outside the range of representable values,
212 \fB\(+-HUGE_VAL\fR, \fB\(+-HUGE_VALF\fR, or \fB\(+-HUGE_VALL\fR is returned
213 (according to the sign of the value), a floating point overflow exception is
214 raised, and \fBerrno\fR is set to \fBERANGE\fR.
215 .sp
216 .LP
217 If the correct value would cause an underflow, the correctly rounded result
218 (which may be normal, subnormal, or zero) is returned, a floating point
219 underflow exception is raised, and \fBerrno\fR is set to \fBERANGE\fR.
220 .SH ERRORS
221 .sp
222 .LP
223 These functions will fail if:
224 .sp
225 .ne 2
226 .na
227 \fB\fBERANGE\fR\fR
228 .ad
229 .RS 10n
230 The value to be returned would cause overflow or underflow
231 .RE
232
233 .sp
234 .LP
235 These functions may fail if:
236 .sp
237 .ne 2
238 .na
239 \fB\fBEINVAL\fR\fR
240 .ad
241 .RS 10n
242 No conversion could be performed.
243 .RE
244
245 .SH USAGE
246 .sp
247 .LP
248 Since 0 is returned on error and is also a valid return on success, an
249 application wishing to check for error situations should set \fBerrno\fR to 0,
250 then call \fBstrtod()\fR, \fBstrtof()\fR, or \fBstrtold()\fR, then check
251 \fBerrno\fR.
252 .sp
253 .LP
254 The changes to \fBstrtod()\fR introduced by the ISO/IEC 9899: 1999 standard can
255 alter the behavior of well-formed applications complying with the ISO/IEC 9899:
256 1990 standard and thus earlier versions of IEEE Std 1003.1-200x. One such
257 example would be:
258 .sp
259 .in +2
260 .nf
261 int
262 what_kind_of_number (char *s)
263 {
264 char *endp;
265 double d;
266 long l;
267 d = strtod(s, &endp);
300 It's an integer with value 16
301 .fi
302 .in -2
303
304 .sp
305 .LP
306 With the ISO/IEC 9899: 1999 standard, the result is:
307 .sp
308 .in +2
309 .nf
310 It's a float with value 16
311 .fi
312 .in -2
313
314 .sp
315 .LP
316 The change in behavior is due to the inclusion of floating-point numbers in
317 hexadecimal notation without requiring that either a decimal point or the
318 binary exponent be present.
319 .SH ATTRIBUTES
320 .sp
321 .LP
322 See \fBattributes\fR(5) for descriptions of the following attributes:
323 .sp
324
325 .sp
326 .TS
327 box;
328 c | c
329 l | l .
330 ATTRIBUTE TYPE ATTRIBUTE VALUE
331 _
332 CSI Enabled
333 _
334 Interface Stability Standard
335 _
336 MT-Level MT-Safe with exceptions
337 .TE
338
339 .SH SEE ALSO
340 .sp
341 .LP
342 \fBisspace\fR(3C), \fBlocaleconv\fR(3C), \fBscanf\fR(3C), \fBsetlocale\fR(3C),
343 \fBstrtol\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)
344 .SH NOTES
345 .sp
346 .LP
347 The \fBstrtod()\fR and \fBatof()\fR functions can be used safely in
348 multithreaded applications, as long as \fBsetlocale\fR(3C) is not called to
349 change the locale.
350 .sp
351 .LP
352 The DESCRIPTION and RETURN VALUES sections above are very similar to the
353 wording used by the Single UNIX Specification version 2 (SUSv2) and the 1989 C
354 Standard to describe the behavior of the \fBstrtod()\fR function. Since some
355 users have reported that they find the description confusing, the following
356 notes might be helpful.
357 .RS +4
358 .TP
359 1.
360 The \fBstrtod()\fR function does not modify the string pointed to by
361 \fIstr\fR and does not \fBmalloc()\fR space to hold the decomposed portions of
362 the input string.
363 .RE
364 .RS +4
365 .TP
366 2.
|
27 .\" The contents of this file are subject to the terms of the
28 .\" Common Development and Distribution License (the "License").
29 .\" You may not use this file except in compliance with the License.
30 .\"
31 .\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
32 .\" or http://www.opensolaris.org/os/licensing.
33 .\" See the License for the specific language governing permissions
34 .\" and limitations under the License.
35 .\"
36 .\" When distributing Covered Code, include this CDDL HEADER in each
37 .\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
38 .\" If applicable, add the following below this CDDL HEADER, with the
39 .\" fields enclosed by brackets "[]" replaced with your own identifying
40 .\" information: Portions Copyright [yyyy] [name of copyright owner]
41 .\"
42 .\"
43 .\" Copyright 1989 AT&T
44 .\" Copyright (c) 1992, X/Open Company Limited. All Rights Reserved.
45 .\" Portions Copyright (c) 2006, Sun Microsystems, Inc. All Rights Reserved.
46 .\"
47 .TH STRTOD 3C "Aug 25, 2019"
48 .SH NAME
49 strtod, strtof, strtold, atof \- convert string to floating-point number
50 .SH SYNOPSIS
51 .nf
52 #include <stdlib.h>
53
54 \fBdouble\fR \fBstrtod\fR(\fBconst char *restrict\fR \fInptr\fR, \fBchar **restrict\fR \fIendptr\fR);
55 .fi
56
57 .LP
58 .nf
59 \fBfloat\fR \fBstrtof\fR(\fBconst char *restrict\fR \fInptr\fR, \fBchar **restrict\fR \fIendptr\fR);
60 .fi
61
62 .LP
63 .nf
64 \fBlong double\fR \fBstrtold\fR(\fBconst char *restrict\fR \fInptr\fR, \fBchar **restrict\fR \fIendptr\fR);
65 .fi
66
67 .LP
68 .nf
69 \fBdouble\fR \fBatof\fR(\fBconst char *\fR\fIstr\fR);
70 .fi
71
72 .SH DESCRIPTION
73 The \fBstrtod()\fR, \fBstrtof()\fR, and \fBstrtold()\fR functions convert the
74 initial portion of the string pointed to by \fInptr\fR to \fBdouble\fR,
75 \fBfloat\fR, and \fBlong double\fR representation, respectively. First they
76 decompose the input string into three parts:
77 .RS +4
78 .TP
79 1.
80 An initial, possibly empty, sequence of white-space characters (as specified
81 by \fBisspace\fR(3C))
82 .RE
83 .RS +4
84 .TP
85 2.
86 A subject sequence interpreted as a floating-point constant or representing
87 infinity or NaN
88 .RE
89 .RS +4
90 .TP
91 3.
92 A final string of one or more unrecognized characters, including the
129 .sp
130 .in +2
131 .nf
132 n-char-sequence:
133 digit
134 nondigit
135 n-char-sequence digit
136 n-char-sequence nondigit
137 .fi
138 .in -2
139
140 .RE
141 .sp
142 .LP
143 In default mode for \fBstrtod()\fR, only decimal, INF/INFINITY, and
144 NAN/NAN(\fIn-char-sequence\fR) forms are recognized. In C99/SUSv3 mode,
145 hexadecimal strings are also recognized.
146 .sp
147 .LP
148 In default mode for \fBstrtod()\fR, the \fIn-char-sequence\fR in the
149 NAN(\fIn-char-sequence\fR) form can contain any character except ')' (right
150 parenthesis) or '\e0' (null). In C99/SUSv3 mode, the \fIn-char-sequence\fR can
151 contain only upper and lower case letters, digits, and '_' (underscore).
152 .sp
153 .LP
154 The \fBstrtof()\fR and \fBstrtold()\fR functions always function in
155 C99/SUSv3-conformant mode.
156 .sp
157 .LP
158 The subject sequence is defined as the longest initial subsequence of the input
159 string, starting with the first non-white-space character, that is of the
160 expected form. The subject sequence contains no characters if the input string
161 is not of the expected form.
162 .sp
163 .LP
164 If the subject sequence has the expected form for a floating-point number, the
165 sequence of characters starting with the first digit or the decimal-point
166 character (whichever occurs first) is interpreted as a floating constant of the
167 C language, except that the radix character is used in place of a period, and
168 that if neither an exponent part nor a radix character appears in a decimal
169 floating-point number, or if a binary exponent part does not appear in a
182 point inexact, underflow, or overflow exceptions as appropriate.
183 .sp
184 .LP
185 The radix character is defined in the program's locale (category
186 \fBLC_NUMERIC\fR). In the POSIX locale, or in a locale where the radix
187 character is not defined, the radix character defaults to a period ('.').
188 .sp
189 .LP
190 If the subject sequence is empty or does not have the expected form, no
191 conversion is performed; the value of \fInptr\fR is stored in the object
192 pointed to by \fIendptr\fR, provided that \fIendptr\fR is not a null pointer.
193 .sp
194 .LP
195 The \fBstrtod()\fR function does not change the setting of \fBerrno\fR if
196 successful.
197 .sp
198 .LP
199 The \fBatof(\fR\fIstr\fR\fB)\fR function call is equivalent to
200 \fBstrtod(\fR\fInptr\fR\fB, (char **)NULL)\fR.
201 .SH RETURN VALUES
202 Upon successful completion, these functions return the converted value. If no
203 conversion could be performed, \fB0\fR is returned.
204 .sp
205 .LP
206 If the correct value is outside the range of representable values,
207 \fB\(+-HUGE_VAL\fR, \fB\(+-HUGE_VALF\fR, or \fB\(+-HUGE_VALL\fR is returned
208 (according to the sign of the value), a floating point overflow exception is
209 raised, and \fBerrno\fR is set to \fBERANGE\fR.
210 .sp
211 .LP
212 If the correct value would cause an underflow, the correctly rounded result
213 (which may be normal, subnormal, or zero) is returned, a floating point
214 underflow exception is raised, and \fBerrno\fR is set to \fBERANGE\fR.
215 .SH ERRORS
216 These functions will fail if:
217 .sp
218 .ne 2
219 .na
220 \fBERANGE\fR
221 .ad
222 .RS 10n
223 The value to be returned would cause overflow or underflow
224 .RE
225
226 .sp
227 .LP
228 These functions may fail if:
229 .sp
230 .ne 2
231 .na
232 \fBEINVAL\fR
233 .ad
234 .RS 10n
235 No conversion could be performed.
236 .RE
237
238 .SH USAGE
239 Since 0 is returned on error and is also a valid return on success, an
240 application wishing to check for error situations should set \fBerrno\fR to 0,
241 then call \fBstrtod()\fR, \fBstrtof()\fR, or \fBstrtold()\fR, then check
242 \fBerrno\fR.
243 .sp
244 .LP
245 The changes to \fBstrtod()\fR introduced by the ISO/IEC 9899: 1999 standard can
246 alter the behavior of well-formed applications complying with the ISO/IEC 9899:
247 1990 standard and thus earlier versions of IEEE Std 1003.1-200x. One such
248 example would be:
249 .sp
250 .in +2
251 .nf
252 int
253 what_kind_of_number (char *s)
254 {
255 char *endp;
256 double d;
257 long l;
258 d = strtod(s, &endp);
291 It's an integer with value 16
292 .fi
293 .in -2
294
295 .sp
296 .LP
297 With the ISO/IEC 9899: 1999 standard, the result is:
298 .sp
299 .in +2
300 .nf
301 It's a float with value 16
302 .fi
303 .in -2
304
305 .sp
306 .LP
307 The change in behavior is due to the inclusion of floating-point numbers in
308 hexadecimal notation without requiring that either a decimal point or the
309 binary exponent be present.
310 .SH ATTRIBUTES
311 See \fBattributes\fR(5) for descriptions of the following attributes:
312 .sp
313
314 .sp
315 .TS
316 box;
317 c | c
318 l | l .
319 ATTRIBUTE TYPE ATTRIBUTE VALUE
320 _
321 CSI Enabled
322 _
323 Interface Stability Standard
324 _
325 MT-Level MT-Safe with exceptions
326 .TE
327
328 .SH SEE ALSO
329 \fBisspace\fR(3C), \fBlocaleconv\fR(3C), \fBscanf\fR(3C), \fBsetlocale\fR(3C),
330 \fBstrtol\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)
331 .SH NOTES
332 The \fBstrtod()\fR and \fBatof()\fR functions can be used safely in
333 multithreaded applications, as long as \fBsetlocale\fR(3C) is not called to
334 change the locale.
335 .sp
336 .LP
337 The DESCRIPTION and RETURN VALUES sections above are very similar to the
338 wording used by the Single UNIX Specification version 2 (SUSv2) and the 1989 C
339 Standard to describe the behavior of the \fBstrtod()\fR function. Since some
340 users have reported that they find the description confusing, the following
341 notes might be helpful.
342 .RS +4
343 .TP
344 1.
345 The \fBstrtod()\fR function does not modify the string pointed to by
346 \fIstr\fR and does not \fBmalloc()\fR space to hold the decomposed portions of
347 the input string.
348 .RE
349 .RS +4
350 .TP
351 2.
|