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
13 strtoul, strtoull — convert a string to an unsigned long
14
16 #include <stdlib.h>
17 unsigned long strtoul(const char *restrict str,
19 char **restrict endptr, int base);
20 unsigned long long strtoull(const char *restrict str,
21 char **restrict endptr, int base);
22
24 The functionality described on this reference page is aligned with the
25 ISO C standard. Any conflict between the requirements described here
26 and the ISO C standard is unintentional. This volume of POSIX.1‐2008
27 defers to the ISO C standard.
28 These functions shall convert the initial portion of the string pointed
30 to by str to a type unsigned long and unsigned long long representa‐
31 tion, respectively. First, they decompose the input string into three
32 parts:
33 1. An initial, possibly empty, sequence of white-space characters (as
35 specified by isspace())
36 2. A subject sequence interpreted as an integer represented in some
38 radix determined by the value of base
39 3. A final string of one or more unrecognized characters, including
41 the terminating NUL character of the input string
42 Then they shall attempt to convert the subject sequence to an unsigned
44 integer, and return the result.
45 If the value of base is 0, the expected form of the subject sequence is
47 that of a decimal constant, octal constant, or hexadecimal constant,
48 any of which may be preceded by a '+' or '−' sign. A decimal constant
49 begins with a non-zero digit, and consists of a sequence of decimal
50 digits. An octal constant consists of the prefix '0' optionally fol‐
51 lowed by a sequence of the digits '0' to '7' only. A hexadecimal con‐
52 stant consists of the prefix 0x or 0X followed by a sequence of the
53 decimal digits and letters 'a' (or 'A') to 'f' (or 'F') with values 10
54 to 15 respectively.
55 If the value of base is between 2 and 36, the expected form of the sub‐
57 ject sequence is a sequence of letters and digits representing an inte‐
58 ger with the radix specified by base, optionally preceded by a '+' or
59 '−' sign. The letters from 'a' (or 'A') to 'z' (or 'Z') inclusive are
60 ascribed the values 10 to 35; only letters whose ascribed values are
61 less than that of base are permitted. If the value of base is 16, the
62 characters 0x or 0X may optionally precede the sequence of letters and
63 digits, following the sign if present.
64 The subject sequence is defined as the longest initial subsequence of
66 the input string, starting with the first non-white-space character
67 that is of the expected form. The subject sequence shall contain no
68 characters if the input string is empty or consists entirely of white-
69 space characters, or if the first non-white-space character is other
70 than a sign or a permissible letter or digit.
71 If the subject sequence has the expected form and the value of base is
73 0, the sequence of characters starting with the first digit shall be
74 interpreted as an integer constant. If the subject sequence has the
75 expected form and the value of base is between 2 and 36, it shall be
76 used as the base for conversion, ascribing to each letter its value as
77 given above. If the subject sequence begins with a minus-sign, the
78 value resulting from the conversion shall be negated. A pointer to the
79 final string shall be stored in the object pointed to by endptr, pro‐
80 vided that endptr is not a null pointer.
81 In other than the C or POSIX locales, other implementation-defined sub‐
83 ject sequences may be accepted.
84 If the subject sequence is empty or does not have the expected form, no
86 conversion shall be performed; the value of str shall be stored in the
87 object pointed to by endptr, provided that endptr is not a null
88 pointer.
89 These functions shall not change the setting of errno if successful.
91 Since 0, {ULONG_MAX}, and {ULLONG_MAX} are returned on error and are
93 also valid returns on success, an application wishing to check for
94 error situations should set errno to 0, then call strtoul() or str‐
95 toull(), then check errno.
96
98 Upon successful completion, these functions shall return the converted
99 value, if any. If no conversion could be performed, 0 shall be returned
100 and errno may be set to [EINVAL].
101 If the value of base is not supported, 0 shall be returned and errno
103 shall be set to [EINVAL].
104 If the correct value is outside the range of representable values,
106 {ULONG_MAX} or {ULLONG_MAX} shall be returned and errno set to
107 [ERANGE].
108
110 These functions shall fail if:
111 EINVAL The value of base is not supported.
113 ERANGE The value to be returned is not representable.
115 These functions may fail if:
117 EINVAL No conversion could be performed.
119 The following sections are informative.
121
123 None.
124
126 Since the value of *endptr is unspecified if the value of base is not
127 supported, applications should either ensure that base has a supported
128 value (0 or between 2 and 36) before the call, or check for an [EINVAL]
129 error before examining *endptr.
130
132 None.
133
135 None.
136
138 fscanf(), isalpha(), strtod(), strtol()
139 The Base Definitions volume of POSIX.1‐2008, <stdlib.h>
141
143 Portions of this text are reprinted and reproduced in electronic form
144 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
145 -- Portable Operating System Interface (POSIX), The Open Group Base
146 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
147 cal and Electronics Engineers, Inc and The Open Group. (This is
148 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
149 event of any discrepancy between this version and the original IEEE and
150 The Open Group Standard, the original IEEE and The Open Group Standard
151 is the referee document. The original Standard can be obtained online
152 at http://www.unix.org/online.html .
153 Any typographical or formatting errors that appear in this page are
155 most likely to have been introduced during the conversion of the source
156 files to man page format. To report such errors, see https://www.ker‐
157 nel.org/doc/man-pages/reporting_bugs.html .
158IEEE/The Open Group 2013 STRTOUL(3P)