1STRTOUL(3P) POSIX Programmer's Manual STRTOUL(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 strtoul, strtoull — convert a string to an unsigned long
13
15 #include <stdlib.h>
16 unsigned long strtoul(const char *restrict str,
18 char **restrict endptr, int base);
19 unsigned long long strtoull(const char *restrict str,
20 char **restrict endptr, int base);
21
23 The functionality described on this reference page is aligned with the
24 ISO C standard. Any conflict between the requirements described here
25 and the ISO C standard is unintentional. This volume of POSIX.1‐2017
26 defers to the ISO C standard.
27 These functions shall convert the initial portion of the string pointed
29 to by str to a type unsigned long and unsigned long long representa‐
30 tion, respectively. First, they decompose the input string into three
31 parts:
32 1. An initial, possibly empty, sequence of white-space characters (as
34 specified by isspace())
35 2. A subject sequence interpreted as an integer represented in some
37 radix determined by the value of base
38 3. A final string of one or more unrecognized characters, including
40 the terminating NUL character of the input string
41 Then they shall attempt to convert the subject sequence to an unsigned
43 integer, and return the result.
44 If the value of base is 0, the expected form of the subject sequence is
46 that of a decimal constant, octal constant, or hexadecimal constant,
47 any of which may be preceded by a '+' or '-' sign. A decimal constant
48 begins with a non-zero digit, and consists of a sequence of decimal
49 digits. An octal constant consists of the prefix '0' optionally fol‐
50 lowed by a sequence of the digits '0' to '7' only. A hexadecimal con‐
51 stant consists of the prefix 0x or 0X followed by a sequence of the
52 decimal digits and letters 'a' (or 'A') to 'f' (or 'F') with values 10
53 to 15 respectively.
54 If the value of base is between 2 and 36, the expected form of the sub‐
56 ject sequence is a sequence of letters and digits representing an inte‐
57 ger with the radix specified by base, optionally preceded by a '+' or
58 '-' sign. The letters from 'a' (or 'A') to 'z' (or 'Z') inclusive are
59 ascribed the values 10 to 35; only letters whose ascribed values are
60 less than that of base are permitted. If the value of base is 16, the
61 characters 0x or 0X may optionally precede the sequence of letters and
62 digits, following the sign if present.
63 The subject sequence is defined as the longest initial subsequence of
65 the input string, starting with the first non-white-space character
66 that is of the expected form. The subject sequence shall contain no
67 characters if the input string is empty or consists entirely of white-
68 space characters, or if the first non-white-space character is other
69 than a sign or a permissible letter or digit.
70 If the subject sequence has the expected form and the value of base is
72 0, the sequence of characters starting with the first digit shall be
73 interpreted as an integer constant. If the subject sequence has the
74 expected form and the value of base is between 2 and 36, it shall be
75 used as the base for conversion, ascribing to each letter its value as
76 given above. If the subject sequence begins with a <hyphen-minus>, the
77 value resulting from the conversion shall be negated. A pointer to the
78 final string shall be stored in the object pointed to by endptr, pro‐
79 vided that endptr is not a null pointer.
80 In other than the C or POSIX locale, additional locale-specific subject
82 sequence forms may be accepted.
83 If the subject sequence is empty or does not have the expected form, no
85 conversion shall be performed; the value of str shall be stored in the
86 object pointed to by endptr, provided that endptr is not a null
87 pointer.
88 These functions shall not change the setting of errno if successful.
90 Since 0, {ULONG_MAX}, and {ULLONG_MAX} are returned on error and are
92 also valid returns on success, an application wishing to check for
93 error situations should set errno to 0, then call strtoul() or str‐
94 toull(), then check errno.
95
97 Upon successful completion, these functions shall return the converted
98 value, if any. If no conversion could be performed, 0 shall be returned
99 and errno may be set to [EINVAL].
100 If the value of base is not supported, 0 shall be returned and errno
102 shall be set to [EINVAL].
103 If the correct value is outside the range of representable values,
105 {ULONG_MAX} or {ULLONG_MAX} shall be returned and errno set to
106 [ERANGE].
107
109 These functions shall fail if:
110 EINVAL The value of base is not supported.
112 ERANGE The value to be returned is not representable.
114 These functions may fail if:
116 EINVAL No conversion could be performed.
118 The following sections are informative.
120
122 None.
123
125 Since the value of *endptr is unspecified if the value of base is not
126 supported, applications should either ensure that base has a supported
127 value (0 or between 2 and 36) before the call, or check for an [EINVAL]
128 error before examining *endptr.
129
131 None.
132
134 None.
135
137 fscanf(), isalpha(), strtod(), strtol()
138 The Base Definitions volume of POSIX.1‐2017, <stdlib.h>
140
142 Portions of this text are reprinted and reproduced in electronic form
143 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
144 table Operating System Interface (POSIX), The Open Group Base Specifi‐
145 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
146 Electrical and Electronics Engineers, Inc and The Open Group. In the
147 event of any discrepancy between this version and the original IEEE and
148 The Open Group Standard, the original IEEE and The Open Group Standard
149 is the referee document. The original Standard can be obtained online
150 at http://www.opengroup.org/unix/online.html .
151 Any typographical or formatting errors that appear in this page are
153 most likely to have been introduced during the conversion of the source
154 files to man page format. To report such errors, see https://www.ker‐
155 nel.org/doc/man-pages/reporting_bugs.html .
156IEEE/The Open Group 2017 STRTOUL(3P)