man3/getdate.3

   1 .\" Copyright 2001 walter harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
   3 .\"     <mtk.manpages@gmail.com>
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  27 .\" Modified, 2001-12-26, aeb
  28 .\" 2008-09-07, mtk, Various rewrites; added an example program.
  29 .\"
  30 .TH GETDATE 3 2010-09-20 "" "Linux Programmer's Manual"
  31 .SH NAME
  32 getdate, getdate_r \- convert a date-plus-time string to broken-down time
  33 .SH SYNOPSIS
  34 .B "#include <time.h>"
  35 .sp
  36 .BI "struct tm *getdate(const char *" string );
  37 .sp
  38 .B "extern int getdate_err;"
  39 .sp
  40 .B "#include <time.h>"
  41 .sp
  42 .BI "int getdate_r(const char *" string ", struct tm *" res );
  43 .sp
  44 .in -4n
  45 Feature Test Macro Requirements for glibc (see
  46 .BR feature_test_macros (7)):
  47 .in
  48 .sp
  49 .BR getdate ():
  50 .ad l
  51 .RS 4
  52 _XOPEN_SOURCE\ >=\ 500 ||
  53 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  54 .RE
  55 .br
  56 .BR getdate_r ():
  57 .ad l
  58 .RS 4
  59 _GNU_SOURCE
  60 .RE
  61 .ad
  62 .SH DESCRIPTION
  63 The function
  64 .BR getdate ()
  65 converts a string representation of a date and time,
  66 contained in the buffer pointed to by
  67 .IR string ,
  68 into a broken-down time.
  69 The broken-down time is stored in a
  70 .I tm
  71 structure, and a pointer to this
  72 structure is returned as the function result.
  73 This
  74 .I tm
  75 structure is allocated in static storage,
  76 and consequently it will be overwritten by further calls to
  77 .BR getdate ().
  78
  79 In contrast to
  80 .BR strptime (3),
  81 (which has a
  82 .I format
  83 argument),
  84 .BR getdate ()
  85 uses the formats found in the file
  86 whose full pathname is given in the environment variable
  87 .BR DATEMSK .
  88 The first line in the file that matches the given input string
  89 is used for the conversion.
  90
  91 The matching is done case insensitively.
  92 Superfluous whitespace, either in the pattern or in the string to
  93 be converted, is ignored.
  94
  95 The conversion specifications that a pattern can contain are those given for
  96 .BR strptime (3).
  97 One more conversion specification is specified in POSIX.1-2001:
  98 .TP
  99 .B %Z
 100 Timezone name.
 101 This is not implemented in glibc.
 102 .LP
 103 When
 104 .B %Z
 105 is given, the structure containing the broken-down time
 106 is initialized with values corresponding to the current
 107 time in the given timezone.
 108 Otherwise, the structure is initialized to the broken-down time
 109 corresponding to the current local time (as by a call to
 110 .BR localtime (3)).
 111 .LP
 112 When only the weekday is given, the day is taken to be the first such day
 113 on or after today.
 114 .LP
 115 When only the month is given (and no year), the month is taken to
 116 be the first such month equal to or after the current month.
 117 If no day is given, it is the first day of the month.
 118 .LP
 119 When no hour, minute and second are given, the current
 120 hour, minute and second are taken.
 121 .LP
 122 If no date is given, but we know the hour, then that hour is taken
 123 to be the first such hour equal to or after the current hour.
 124
 125 .BR getdate_r ()
 126 is a GNU extension that provides a reentrant version of
 127 .BR getdate ().
 128 Rather than using a global variable to report errors and a static buffer
 129 to return the broken down time,
 130 it returns errors via the function result value,
 131 and returns the resulting broken-down time in the
 132 caller-allocated buffer pointed to by the argument
 133 .IR res .
 134 .SH RETURN VALUE
 135 When successful,
 136 .BR getdate ()
 137 returns a pointer to a
 138 .IR "struct tm" .
 139 Otherwise, it returns NULL and sets the global variable
 140 .IR getdate_err
 141 to one of the error numbers shown below.
 142 Changes to
 143 .I errno
 144 are unspecified.
 145
 146 On success
 147 .BR getdate_r ()
 148 returns 0;
 149 on error it returns one of the error numbers shown below.
 150 .SH ERRORS
 151 The following errors are returned via
 152 .IR getdate_err
 153 (for
 154 .BR getdate ())
 155 or as the function result (for
 156 .BR getdate_r ()):
 157 .TP 4n
 158 .B 1
 159 The
 160 .B DATEMSK
 161 environment variable is not defined, or its value is an empty string.
 162 .TP
 163 .B 2
 164 The template file specified by
 165 .B DATEMSK
 166 cannot be opened for reading.
 167 .TP
 168 .B 3
 169 Failed to get file status information.
 170 .\" stat()
 171 .TP
 172 .B 4
 173 The template file is not a regular file.
 174 .TP
 175 .B 5
 176 An error was encountered while reading the template file.
 177 .TP
 178 .B 6
 179 Memory allocation failed (not enough memory available).
 180 .\" Error 6 doesn't seem to occur in glibc
 181 .TP
 182 .B 7
 183 There is no line in the file that matches the input.
 184 .TP
 185 .B 8
 186 Invalid input specification.
 187 .SH ENVIRONMENT
 188 .TP
 189 .B DATEMSK
 190 File containing format patterns.
 191 .TP
 192 .BR TZ ", " LC_TIME
 193 Variables used by
 194 .BR strptime (3).
 195 .SH ATTRIBUTES
 196 .SS Multithreading (see pthreads(7))
 197 The
 198 .BR getdate ()
 199 function is not thread-safe.
 200 .LP
 201 The
 202 .BR getdate_r ()
 203 function is thread-safe.
 204 .SH CONFORMING TO
 205 POSIX.1-2001.
 206 .SH NOTES
 207 The POSIX.1-2001 specification for
 208 .BR strptime (3)
 209 contains conversion specifications using the
 210 .B %E
 211 or
 212 .B %O
 213 modifier, while such specifications are not given for
 214 .BR getdate ().
 215 In glibc,
 216 .BR getdate ()
 217 is implemented using
 218 .BR strptime (3),
 219 so that precisely the same conversions are supported by both.
 220 .SH EXAMPLE
 221 The program below calls
 222 .BR getdate ()
 223 for each of its command-line arguments,
 224 and for each call displays the values in the fields of the returned
 225 .I tm
 226 structure.
 227 The following shell session demonstrates the operation of the program:
 228
 229 .in +4n
 230 .nf
 231 .RB "$" " TFILE=$PWD/tfile"
 232 .RB "$" " echo \(aq%A\(aq > $TFILE " "      # Full weekday name"
 233 .RB "$" " echo \(aq%T\(aq >> $TFILE" "      # ISO date (YYYY-MM-DD)"
 234 .RB "$" " echo \(aq%F\(aq >> $TFILE" "      # Time (HH:MM:SS)"
 235 .RB "$" " date"
 236 .RB "$" " export DATEMSK=$TFILE"
 237 .RB "$" " ./a.out Tuesday \(aq2009-12-28\(aq \(aq12:22:33\(aq"
 238 Sun Sep  7 06:03:36 CEST 2008
 239 Call 1 ("Tuesday") succeeded:
 240     tm_sec   = 36
 241     tm_min   = 3
 242     tm_hour  = 6
 243     tm_mday  = 9
 244     tm_mon   = 8
 245     tm_year  = 108
 246     tm_wday  = 2
 247     tm_yday  = 252
 248     tm_isdst = 1
 249 Call 2 ("2009-12-28") succeeded:
 250     tm_sec   = 36
 251     tm_min   = 3
 252     tm_hour  = 6
 253     tm_mday  = 28
 254     tm_mon   = 11
 255     tm_year  = 109
 256     tm_wday  = 1
 257     tm_yday  = 361
 258     tm_isdst = 0
 259 Call 3 ("12:22:33") succeeded:
 260     tm_sec   = 33
 261     tm_min   = 22
 262     tm_hour  = 12
 263     tm_mday  = 7
 264     tm_mon   = 8
 265     tm_year  = 108
 266     tm_wday  = 0
 267     tm_yday  = 250
 268     tm_isdst = 1
 269 .fi
 270 .in
 271 .SS Program source
 272 \&
 273 .nf
 274 #define _GNU_SOURCE 500
 275 #include <time.h>
 276 #include <stdio.h>
 277 #include <stdlib.h>
 278
 279 int
 280 main(int argc, char *argv[])
 281 {
 282     struct tm *tmp;
 283     int j;
 284
 285     for (j = 1; j < argc; j++) {
 286         tmp = getdate(argv[j]);
 287
 288         if (tmp == NULL) {
 289             printf("Call %d failed; getdate_err = %d\\n",
 290                    j, getdate_err);
 291             continue;
 292         }
 293
 294         printf("Call %d (\\"%s\\") succeeded:\\n", j, argv[j]);
 295         printf("    tm_sec   = %d\\n", tmp\->tm_sec);
 296         printf("    tm_min   = %d\\n", tmp\->tm_min);
 297         printf("    tm_hour  = %d\\n", tmp\->tm_hour);
 298         printf("    tm_mday  = %d\\n", tmp\->tm_mday);
 299         printf("    tm_mon   = %d\\n", tmp\->tm_mon);
 300         printf("    tm_year  = %d\\n", tmp\->tm_year);
 301         printf("    tm_wday  = %d\\n", tmp\->tm_wday);
 302         printf("    tm_yday  = %d\\n", tmp\->tm_yday);
 303         printf("    tm_isdst = %d\\n", tmp\->tm_isdst);
 304     }
 305
 306     exit(EXIT_SUCCESS);
 307 }
 308 .fi
 309 .SH SEE ALSO
 310 .BR time (2),
 311 .BR localtime (3),
 312 .BR setlocale (3),
 313 .BR strftime (3),
 314 .BR strptime (3)