stdtime/strptime.3

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  26 .\" $FreeBSD: src/lib/libc/stdtime/strptime.3,v 1.23 2004/07/02 23:52:12 ru Exp $
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  28 .Dd January 4, 2003
  29 .Dt STRPTIME 3
  30 .Os
  31 .Sh NAME
  32 .Nm strptime ,
  33 .Nm strptime_l
  34 .Nd parse date and time string
  35 .Sh LIBRARY
  36 .Lb libc
  37 .Sh SYNOPSIS
  38 .In time.h
  39 .Ft char *
  40 .Fo strptime
  41 .Fa "const char *restrict buf"
  42 .Fa "const char *restrict format"
  43 .Fa "struct tm *restrict tm"
  44 .Fc
  45 .In time.h
  46 .In xlocale.h
  47 .Ft char *
  48 .Fo strptime_l
  49 .Fa "const char *restrict buf"
  50 .Fa "const char *restrict format"
  51 .Fa "struct tm *restrict tm"
  52 .Fa "locale_t loc"
  53 .Fc
  54 .Sh DESCRIPTION
  55 The
  56 .Fn strptime
  57 function parses the string in the buffer
  58 .Fa buf ,
  59 according to the string pointed to by
  60 .Fa format ,
  61 and fills in the elements of the structure pointed to by
  62 .Fa tm .
  63 The resulting values will be relative to the local time zone.
  64 Thus, it can be considered the reverse operation of
  65 .Xr strftime 3 .
  66 .Pp
  67 The
  68 .Fa format
  69 string consists of zero or more conversion specifications and
  70 ordinary characters.
  71 All ordinary characters are matched exactly with the buffer, where
  72 white space in the format string will match any amount of white space
  73 in the buffer.
  74 All conversion specifications are identical to those described in
  75 .Xr strftime 3 .
  76 .Pp
  77 Two-digit year values, including formats
  78 .Fa %y
  79 and
  80 .Fa \&%D ,
  81 are now interpreted as beginning at 1969 per POSIX requirements.
  82 Years 69-00 are interpreted in the 20th century (1969-2000), years
  83 01-68 in the 21st century (2001-2068).
  84 .Pp
  85 If the
  86 .Fa format
  87 string does not contain enough conversion specifications to completely
  88 specify the resulting
  89 .Vt struct tm ,
  90 the unspecified members of
  91 .Va tm
  92 are left untouched.
  93 For example, if
  94 .Fa format
  95 is
  96 .Dq Li "%H:%M:%S" ,
  97 only
  98 .Va tm_hour ,
  99 .Va tm_sec
 100 and
 101 .Va tm_min
 102 will be modified.
 103 If time relative to today is desired, initialize the
 104 .Fa tm
 105 structure with today's date before passing it to
 106 .Fn strptime .
 107 .Pp
 108 While the
 109 .Fn strptime
 110 function uses the current locale, the
 111 .Fn strptime_l
 112 function may be passed a locale directly. See
 113 .Xr xlocale 3
 114 for more information.
 115 .Sh RETURN VALUES
 116 Upon successful completion,
 117 .Fn strptime
 118 returns the pointer to the first character in
 119 .Fa buf
 120 that has not been required to satisfy the specified conversions in
 121 .Fa format .
 122 It returns
 123 .Dv NULL
 124 if one of the conversions failed.
 125 .Sh LEGACY DESCRIPTION
 126 In legacy mode, the
 127 .Fa %Y
 128 format specifier expects exactly 4 digits (leaving any trailing digits for the
 129 next specifier).
 130 .Sh SEE ALSO
 131 .Xr date 1 ,
 132 .Xr scanf 3 ,
 133 .Xr strftime 3 ,
 134 .Xr xlocale 3
 135 .Sh AUTHORS
 136 The
 137 .Fn strptime
 138 function has been contributed by Powerdog Industries.
 139 .Pp
 140 This man page was written by
 141 .An J\(:org Wunsch .
 142 .Sh HISTORY
 143 The
 144 .Fn strptime
 145 function appeared in
 146 .Fx 3.0 .
 147 .Sh BUGS
 148 Both the
 149 .Fa %e
 150 and
 151 .Fa %l
 152 format specifiers may incorrectly scan one too many digits
 153 if the intended values comprise only a single digit
 154 and that digit is followed immediately by another digit.
 155 Both specifiers accept zero-padded values,
 156 even though they are both defined as taking unpadded values.
 157 .Pp
 158 The
 159 .Fa %p
 160 format specifier has no effect unless it is parsed
 161 .Em after
 162 hour-related specifiers.
 163 Specifying
 164 .Fa %l
 165 without
 166 .Fa %p
 167 will produce undefined results.
 168 Note that 12AM
 169 (ante meridiem)
 170 is taken as midnight
 171 and 12PM
 172 (post meridiem)
 173 is taken as noon.
 174 .Pp
 175 The
 176 .Fa %U
 177 and
 178 .Fa %W
 179 format specifiers accept any value within the range 00 to 53
 180 without validating against other values supplied (like month
 181 or day of the year, for example).
 182 .Pp
 183 The
 184 .Fa %Z
 185 format specifier only accepts time zone abbreviations of the local time zone,
 186 or the value "GMT".
 187 This limitation is because of ambiguity due to of the over loading of time
 188 zone abbreviations.
 189 One such example is
 190 .Fa EST
 191 which is both Eastern Standard Time and Eastern Australia Summer Time.
 192 .Pp
 193 The
 194 .Fn strptime
 195 function does not correctly handle multibyte characters in the
 196 .Fa format
 197 argument.