stdtime/FreeBSD/strptime.3

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  26 .\" $FreeBSD: src/lib/libc/stdtime/strptime.3,v 1.22 2003/01/04 09:50:04 tjr Exp $
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  28 .Dd January 4, 2003
  29 .Dt STRPTIME 3
  30 .Os
  31 .Sh NAME
  32 .Nm strptime
  33 .Nd parse date and time string
  34 .Sh LIBRARY
  35 .Lb libc
  36 .Sh SYNOPSIS
  37 .In time.h
  38 .Ft char *
  39 .Fo strptime
  40 .Fa "const char * restrict buf"
  41 .Fa "const char * restrict format"
  42 .Fa "struct tm * restrict timeptr"
  43 .Fc
  44 .Sh DESCRIPTION
  45 The
  46 .Fn strptime
  47 function parses the string in the buffer
  48 .Fa buf
  49 according to the string pointed to by
  50 .Fa format ,
  51 and fills in the elements of the structure pointed to by
  52 .Fa timeptr .
  53 The resulting values will be relative to the local time zone.
  54 Thus, it can be considered the reverse operation of
  55 .Xr strftime 3 .
  56 .Pp
  57 The
  58 .Fa format
  59 string consists of zero or more conversion specifications and
  60 ordinary characters.
  61 All ordinary characters are matched exactly with the buffer, where
  62 white space in the format string will match any amount of white space
  63 in the buffer.
  64 All conversion specifications are identical to those described in
  65 .Xr strftime 3 .
  66 .Pp
  67 Two-digit year values, including formats
  68 .Fa %y
  69 and
  70 .Fa \&%D ,
  71 are now interpreted as beginning at 1969 per POSIX requirements.
  72 Years 69-00 are interpreted in the 20th century (1969-2000), years
  73 01-68 in the 21st century (2001-2068).
  74 .Pp
  75 If the
  76 .Fa format
  77 string does not contain enough conversion specifications to completely
  78 specify the resulting
  79 .Vt struct tm ,
  80 the unspecified members of
  81 .Va timeptr
  82 are left untouched.
  83 For example, if
  84 .Fa format
  85 is
  86 .Dq Li "%H:%M:%S" ,
  87 only
  88 .Va tm_hour ,
  89 .Va tm_sec
  90 and
  91 .Va tm_min
  92 will be modified.
  93 If time relative to today is desired, initialize the
  94 .Fa timeptr
  95 structure with today's date before passing it to
  96 .Fn strptime .
  97 .Sh RETURN VALUES
  98 Upon successful completion,
  99 .Fn strptime
 100 returns the pointer to the first character in
 101 .Fa buf
 102 that has not been required to satisfy the specified conversions in
 103 .Fa format .
 104 It returns
 105 .Dv NULL
 106 if one of the conversions failed.
 107 .Sh SEE ALSO
 108 .Xr date 1 ,
 109 .Xr scanf 3 ,
 110 .Xr strftime 3
 111 .Sh AUTHORS
 112 The
 113 .Fn strptime
 114 function has been contributed by Powerdog Industries.
 115 .Pp
 116 This man page was written by
 117 .An J\(:org Wunsch .
 118 .Sh HISTORY
 119 The
 120 .Fn strptime
 121 function appeared in
 122 .Fx 3.0 .
 123 .Sh BUGS
 124 Both the
 125 .Fa %e
 126 and
 127 .Fa %l
 128 format specifiers may incorrectly scan one too many digits
 129 if the intended values comprise only a single digit
 130 and that digit is followed immediately by another digit.
 131 Both specifiers accept zero-padded values,
 132 even though they are both defined as taking unpadded values.
 133 .Pp
 134 The
 135 .Fa %p
 136 format specifier has no effect unless it is parsed
 137 .Em after
 138 hour-related specifiers.
 139 Specifying
 140 .Fa %l
 141 without
 142 .Fa %p
 143 will produce undefined results.
 144 Note that 12AM
 145 (ante meridiem)
 146 is taken as midnight
 147 and 12PM
 148 (post meridiem)
 149 is taken as noon.
 150 .Pp
 151 The
 152 .Fa %U
 153 and
 154 .Fa %W
 155 format specifiers accept any value within the range 00 to 53
 156 without validating against other values supplied (like month
 157 or day of the year, for example).
 158 .Pp
 159 The
 160 .Fa %Z
 161 format specifier only accepts time zone abbreviations of the local time zone,
 162 or the value "GMT".
 163 This limitation is because of ambiguity due to of the over loading of time
 164 zone abbreviations.  One such example is
 165 .Fa EST
 166 which is both Eastern Standard Time and Eastern Australia Summer Time.
 167 .Pp
 168 The
 169 .Fn strptime
 170 function does not correctly handle multibyte characters in the
 171 .Fa format
 172 argument.