man3/strtoul.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  23 .\" References consulted:
  24 .\"     Linux libc source code
  25 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  26 .\"     386BSD man pages
  27 .\" Modified Sun Jul 25 10:54:03 1993 by Rik Faith (faith@cs.unc.edu)
  28 .\" Fixed typo, aeb, 950823
  29 .\" 2002-02-22, joey, mihtjel: Added strtoull()
  30 .\"
  31 .TH STRTOUL 3  2002-05-30 "GNU" "Linux Programmer's Manual"
  32 .SH NAME
  33 strtoul, strtoull, strtouq \- convert a string to an unsigned long integer
  34 .SH SYNOPSIS
  35 .nf
  36 .B #include <stdlib.h>
  37 .sp
  38 .BI "unsigned long int"
  39 .BI "strtoul(const char *" nptr ", char **" endptr ", int " base );
  40 .sp
  41 .BI "unsigned long long int"
  42 .BI "strtoull(const char *" nptr ", char **" endptr ", int " base );
  43 .fi
  44 .SH DESCRIPTION
  45 The
  46 .BR strtoul ()
  47 function converts the initial part of the string
  48 in \fInptr\fP to an unsigned long integer value according to the
  49 given \fIbase\fP, which must be between 2 and 36 inclusive, or be
  50 the special value 0.
  51 .PP
  52 The string may begin with an arbitrary amount of white space (as
  53 determined by
  54 .BR isspace (3))
  55 followed by a single optional `+' or `\-'
  56 sign.
  57 If \fIbase\fP is zero or 16, the string may then include a
  58 `0x' prefix, and the number will be read in base 16; otherwise, a
  59 zero \fIbase\fP is taken as 10 (decimal) unless the next character
  60 is `0', in which case it is taken as 8 (octal).
  61 .PP
  62 The remainder of the string is converted to an unsigned long int value
  63 in the obvious manner, stopping at the first character which is not a
  64 valid digit in the given base.
  65 (In bases above 10, the letter `A' in
  66 either upper or lower case represents 10, `B' represents 11, and so
  67 forth, with `Z' representing 35.)
  68 .PP
  69 If \fIendptr\fP is not NULL,
  70 .BR strtoul ()
  71 stores the address of the
  72 first invalid character in \fI*endptr\fP.
  73 If there were no digits at
  74 all,
  75 .BR strtoul ()
  76 stores the original value of \fInptr\fP in
  77 \fI*endptr\fP (and returns 0).
  78 In particular, if \fI*nptr\fP is not `\\0' but \fI**endptr\fP
  79 is `\\0' on return, the entire string is valid.
  80 .PP
  81 The
  82 .BR strtoull ()
  83 function works just like the
  84 .BR strtoul ()
  85 function but returns an unsigned long long integer value.
  86 .SH "RETURN VALUE"
  87 The
  88 .BR strtoul ()
  89 function returns either the result of the conversion
  90 or, if there was a leading minus sign, the negation of the result of the
  91 conversion represented as an unsigned value,
  92 unless the original (non-negated) value would overflow; in
  93 the latter case,
  94 .BR strtoul ()
  95 returns ULONG_MAX and sets the global
  96 variable \fIerrno\fP to ERANGE.
  97 Precisely the same holds for
  98 .BR strtoull ()
  99 (with ULLONG_MAX instead of ULONG_MAX).
 100 .SH ERRORS
 101 .TP
 102 .B EINVAL
 103 (not in C99)
 104 The given
 105 .I base
 106 contains an unsupported value.
 107 .TP
 108 .B ERANGE
 109 The resulting value was out of range.
 110 .LP
 111 The implementation may also set \fIerrno\fP to \fBEINVAL\fP in case
 112 no conversion was performed (no digits seen, and 0 returned).
 113 .SH "CONFORMING TO"
 114 .BR strtoul ()
 115 conforms to SVr4, C89, C99 and POSIX-2001, and
 116 .BR strtoull ()
 117 to C99 and POSIX.1-2001.
 118 .SH NOTES
 119 Since
 120 .BR strtoul ()
 121 can legitimately return 0 or LONG_MAX (LLONG_MAX for
 122 .BR strtoull ())
 123 on both success and failure, the calling program should set
 124 .I errno
 125 to 0 before the call,
 126 and then determine if an error occurred by checking whether
 127 .I errno
 128 has a non-zero value after the call.
 129
 130 In locales other than the "C" locale, other strings may be accepted.
 131 (For example, the thousands separator of the current locale may be
 132 supported.)
 133 .LP
 134 BSD also has
 135 .sp
 136 .in +4n
 137 .nf
 138 .BI "u_quad_t"
 139 .BI "strtouq(const char *" nptr ", char **" endptr ", int base" );
 140 .sp
 141 .in -4n
 142 .fi
 143 with completely analogous definition.
 144 Depending on the wordsize of the current architecture, this
 145 may be equivalent to
 146 .BR strtoull ()
 147 or to
 148 .BR strtoul ().
 149
 150 Negative values are considered valid input and are
 151 silently converted to the equivalent unsigned long value.
 152 .SH EXAMPLE
 153 See the example on the
 154 .BR strtol (3)
 155 manual page;
 156 the use of the functions described in this manual page is similar.
 157 .SH "SEE ALSO"
 158 .BR atof (3),
 159 .BR atoi (3),
 160 .BR atol (3),
 161 .BR strtod (3),
 162 .BR strtol (3)