man3/strtoul.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\" Modified Sun Jul 25 10:54:03 1993 by Rik Faith (faith@cs.unc.edu)
  30 .\" Fixed typo, aeb, 950823
  31 .\" 2002-02-22, joey, mihtjel: Added strtoull()
  32 .\"
  33 .TH STRTOUL 3  2019-03-06 "GNU" "Linux Programmer's Manual"
  34 .SH NAME
  35 strtoul, strtoull, strtouq \- convert a string to an unsigned long integer
  36 .SH SYNOPSIS
  37 .nf
  38 .B #include <stdlib.h>
  39 .PP
  40 .BI "unsigned long int strtoul(const char *" nptr ", char **" endptr \
  41 ", int " base );
  42 .PP
  43 .BI "unsigned long long int strtoull(const char *" nptr ", char **" endptr ,
  44 .BI "                                int " base );
  45 .fi
  46 .PP
  47 .in -4n
  48 Feature Test Macro Requirements for glibc (see
  49 .BR feature_test_macros (7)):
  50 .in
  51 .PP
  52 .ad l
  53 .BR strtoull ():
  54 .RS 4
  55 _ISOC99_SOURCE ||
  56     || /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
  57 .RE
  58 .ad
  59 .SH DESCRIPTION
  60 The
  61 .BR strtoul ()
  62 function converts the initial part of the string
  63 in
  64 .I nptr
  65 to an
  66 .I "unsigned long int"
  67 value according to the
  68 given
  69 .IR base ,
  70 which must be between 2 and 36 inclusive, or be
  71 the special value 0.
  72 .PP
  73 The string may begin with an arbitrary amount of white space (as
  74 determined by
  75 .BR isspace (3))
  76 followed by a single optional \(aq+\(aq or \(aq\-\(aq
  77 sign.
  78 If
  79 .I base
  80 is zero or 16, the string may then include a
  81 "0x" prefix, and the number will be read in base 16; otherwise, a
  82 zero
  83 .I base
  84 is taken as 10 (decimal) unless the next character
  85 is \(aq0\(aq, in which case it is taken as 8 (octal).
  86 .PP
  87 The remainder of the string is converted to an
  88 .I "unsigned long int"
  89 value in the obvious manner,
  90 stopping at the first character which is not a
  91 valid digit in the given base.
  92 (In bases above 10, the letter \(aqA\(aq in
  93 either uppercase or lowercase represents 10, \(aqB\(aq represents 11, and so
  94 forth, with \(aqZ\(aq representing 35.)
  95 .PP
  96 If
  97 .I endptr
  98 is not NULL,
  99 .BR strtoul ()
 100 stores the address of the
 101 first invalid character in
 102 .IR *endptr .
 103 If there were no digits at
 104 all,
 105 .BR strtoul ()
 106 stores the original value of
 107 .I nptr
 108 in
 109 .I *endptr
 110 (and returns 0).
 111 In particular, if
 112 .I *nptr
 113 is not \(aq\e0\(aq but
 114 .I **endptr
 115 is \(aq\e0\(aq on return, the entire string is valid.
 116 .PP
 117 The
 118 .BR strtoull ()
 119 function works just like the
 120 .BR strtoul ()
 121 function but returns an
 122 .I "unsigned long long int"
 123 value.
 124 .SH RETURN VALUE
 125 The
 126 .BR strtoul ()
 127 function returns either the result of the conversion
 128 or, if there was a leading minus sign, the negation of the result of the
 129 conversion represented as an unsigned value,
 130 unless the original (nonnegated) value would overflow; in
 131 the latter case,
 132 .BR strtoul ()
 133 returns
 134 .B ULONG_MAX
 135 and sets
 136 .I errno
 137 to
 138 .BR ERANGE .
 139 Precisely the same holds for
 140 .BR strtoull ()
 141 (with
 142 .B ULLONG_MAX
 143 instead of
 144 .BR ULONG_MAX ).
 145 .SH ERRORS
 146 .TP
 147 .B EINVAL
 148 (not in C99)
 149 The given
 150 .I base
 151 contains an unsupported value.
 152 .TP
 153 .B ERANGE
 154 The resulting value was out of range.
 155 .PP
 156 The implementation may also set
 157 .IR errno
 158 to
 159 .B EINVAL
 160 in case
 161 no conversion was performed (no digits seen, and 0 returned).
 162 .SH ATTRIBUTES
 163 For an explanation of the terms used in this section, see
 164 .BR attributes (7).
 165 .TS
 166 allbox;
 167 lbw32 lb lb
 168 l l l.
 169 Interface       Attribute       Value
 170 T{
 171 .BR strtoul (),
 172 .BR strtoull (),
 173 .BR strtouq ()
 174 T}      Thread safety   MT-Safe locale
 175 .TE
 176 .SH CONFORMING TO
 177 .BR strtoul ():
 178 POSIX.1-2001, POSIX.1-2008, C89, C99 SVr4.
 179 .PP
 180 .BR strtoull ():
 181 POSIX.1-2001, POSIX.1-2008, C99.
 182 .SH NOTES
 183 Since
 184 .BR strtoul ()
 185 can legitimately return 0 or
 186 .B ULONG_MAX
 187 .RB ( ULLONG_MAX
 188 for
 189 .BR strtoull ())
 190 on both success and failure, the calling program should set
 191 .I errno
 192 to 0 before the call,
 193 and then determine if an error occurred by checking whether
 194 .I errno
 195 has a nonzero value after the call.
 196 .PP
 197 In locales other than the "C" locale, other strings may be accepted.
 198 (For example, the thousands separator of the current locale may be
 199 supported.)
 200 .PP
 201 BSD also has
 202 .PP
 203 .in +4n
 204 .EX
 205 .BI "u_quad_t strtouq(const char *" nptr ", char **" endptr ", int " base );
 206 .EE
 207 .in
 208 .PP
 209 with completely analogous definition.
 210 Depending on the wordsize of the current architecture, this
 211 may be equivalent to
 212 .BR strtoull ()
 213 or to
 214 .BR strtoul ().
 215 .PP
 216 Negative values are considered valid input and are
 217 silently converted to the equivalent
 218 .I "unsigned long int"
 219 value.
 220 .SH EXAMPLE
 221 See the example on the
 222 .BR strtol (3)
 223 manual page;
 224 the use of the functions described in this manual page is similar.
 225 .SH SEE ALSO
 226 .BR a64l (3),
 227 .BR atof (3),
 228 .BR atoi (3),
 229 .BR atol (3),
 230 .BR strtod (3),
 231 .BR strtol (3),
 232 .BR strtoumax (3)