man3/getdate.3

   1 '\" t
   2 .\" Copyright 2001 walter harms (walter.harms@informatik.uni-oldenburg.de)
   3 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
   4 .\"     <mtk.manpages@gmail.com>
   5 .\"
   6 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   7 .\"
   8 .\" Modified, 2001-12-26, aeb
   9 .\" 2008-09-07, mtk, Various rewrites; added an example program.
  10 .\"
  11 .TH getdate 3 (date) "Linux man-pages (unreleased)"
  12 .SH NAME
  13 getdate, getdate_r \- convert a date-plus-time string to broken-down time
  14 .SH LIBRARY
  15 Standard C library
  16 .RI ( libc ", " \-lc )
  17 .SH SYNOPSIS
  18 .nf
  19 .B "#include <time.h>"
  20 .PP
  21 .BI "struct tm *getdate(const char *" string );
  22 .PP
  23 .B "extern int getdate_err;"
  24 .PP
  25 .BI "int getdate_r(const char *restrict " string ", struct tm *restrict " res );
  26 .fi
  27 .PP
  28 .RS -4
  29 Feature Test Macro Requirements for glibc (see
  30 .BR feature_test_macros (7)):
  31 .RE
  32 .PP
  33 .BR getdate ():
  34 .nf
  35     _XOPEN_SOURCE >= 500
  36 .\"    || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
  37 .fi
  38 .PP
  39 .BR getdate_r ():
  40 .nf
  41     _GNU_SOURCE
  42 .fi
  43 .SH DESCRIPTION
  44 The function
  45 .BR getdate ()
  46 converts a string representation of a date and time,
  47 contained in the buffer pointed to by
  48 .IR string ,
  49 into a broken-down time.
  50 The broken-down time is stored in a
  51 .I tm
  52 structure, and a pointer to this
  53 structure is returned as the function result.
  54 This
  55 .I tm
  56 structure is allocated in static storage,
  57 and consequently it will be overwritten by further calls to
  58 .BR getdate ().
  59 .PP
  60 In contrast to
  61 .BR strptime (3),
  62 (which has a
  63 .I format
  64 argument),
  65 .BR getdate ()
  66 uses the formats found in the file
  67 whose full pathname is given in the environment variable
  68 .BR DATEMSK .
  69 The first line in the file that matches the given input string
  70 is used for the conversion.
  71 .PP
  72 The matching is done case insensitively.
  73 Superfluous whitespace, either in the pattern or in the string to
  74 be converted, is ignored.
  75 .PP
  76 The conversion specifications that a pattern can contain are those given for
  77 .BR strptime (3).
  78 One more conversion specification is specified in POSIX.1-2001:
  79 .TP
  80 .B %Z
  81 Timezone name.
  82 .\" FIXME Is it (still) true that %Z is not supported in glibc?
  83 .\" Looking at the glibc 2.21 source code, where the implementation uses
  84 .\" strptime(), suggests that it might be supported.
  85 This is not implemented in glibc.
  86 .PP
  87 When
  88 .B %Z
  89 is given, the structure containing the broken-down time
  90 is initialized with values corresponding to the current
  91 time in the given timezone.
  92 Otherwise, the structure is initialized to the broken-down time
  93 corresponding to the current local time (as by a call to
  94 .BR localtime (3)).
  95 .PP
  96 When only the day of the week is given,
  97 the day is taken to be the first such day
  98 on or after today.
  99 .PP
 100 When only the month is given (and no year), the month is taken to
 101 be the first such month equal to or after the current month.
 102 If no day is given, it is the first day of the month.
 103 .PP
 104 When no hour, minute, and second are given, the current
 105 hour, minute, and second are taken.
 106 .PP
 107 If no date is given, but we know the hour, then that hour is taken
 108 to be the first such hour equal to or after the current hour.
 109 .PP
 110 .BR getdate_r ()
 111 is a GNU extension that provides a reentrant version of
 112 .BR getdate ().
 113 Rather than using a global variable to report errors and a static buffer
 114 to return the broken down time,
 115 it returns errors via the function result value,
 116 and returns the resulting broken-down time in the
 117 caller-allocated buffer pointed to by the argument
 118 .IR res .
 119 .SH RETURN VALUE
 120 When successful,
 121 .BR getdate ()
 122 returns a pointer to a
 123 .IR "struct tm" .
 124 Otherwise, it returns NULL and sets the global variable
 125 .I getdate_err
 126 to one of the error numbers shown below.
 127 Changes to
 128 .I errno
 129 are unspecified.
 130 .PP
 131 On success
 132 .BR getdate_r ()
 133 returns 0;
 134 on error it returns one of the error numbers shown below.
 135 .SH ERRORS
 136 The following errors are returned via
 137 .I getdate_err
 138 (for
 139 .BR getdate ())
 140 or as the function result (for
 141 .BR getdate_r ()):
 142 .TP 4n
 143 .B 1
 144 The
 145 .B DATEMSK
 146 environment variable is not defined, or its value is an empty string.
 147 .TP
 148 .B 2
 149 The template file specified by
 150 .B DATEMSK
 151 cannot be opened for reading.
 152 .TP
 153 .B 3
 154 Failed to get file status information.
 155 .\" stat()
 156 .TP
 157 .B 4
 158 The template file is not a regular file.
 159 .TP
 160 .B 5
 161 An error was encountered while reading the template file.
 162 .TP
 163 .B 6
 164 Memory allocation failed (not enough memory available).
 165 .\" Error 6 doesn't seem to occur in glibc
 166 .TP
 167 .B 7
 168 There is no line in the file that matches the input.
 169 .TP
 170 .B 8
 171 Invalid input specification.
 172 .SH ENVIRONMENT
 173 .TP
 174 .B DATEMSK
 175 File containing format patterns.
 176 .TP
 177 .BR TZ ", " LC_TIME
 178 Variables used by
 179 .BR strptime (3).
 180 .SH ATTRIBUTES
 181 For an explanation of the terms used in this section, see
 182 .BR attributes (7).
 183 .ad l
 184 .nh
 185 .TS
 186 allbox;
 187 lb lb lbx
 188 l l l.
 189 Interface       Attribute       Value
 190 T{
 191 .BR getdate ()
 192 T}      Thread safety   T{
 193 MT-Unsafe race:getdate env locale
 194 T}
 195 T{
 196 .BR getdate_r ()
 197 T}      Thread safety   T{
 198 MT-Safe env locale
 199 T}
 200 .TE
 201 .hy
 202 .ad
 203 .sp 1
 204 .SH VERSIONS
 205 The POSIX.1 specification for
 206 .BR strptime (3)
 207 contains conversion specifications using the
 208 .B %E
 209 or
 210 .B %O
 211 modifier, while such specifications are not given for
 212 .BR getdate ().
 213 In glibc,
 214 .BR getdate ()
 215 is implemented using
 216 .BR strptime (3),
 217 so that precisely the same conversions are supported by both.
 218 .SH STANDARDS
 219 POSIX.1-2008.
 220 .SH HISTORY
 221 POSIX.1-2001.
 222 .SH EXAMPLES
 223 The program below calls
 224 .BR getdate ()
 225 for each of its command-line arguments,
 226 and for each call displays the values in the fields of the returned
 227 .I tm
 228 structure.
 229 The following shell session demonstrates the operation of the program:
 230 .PP
 231 .in +4n
 232 .EX
 233 .RB "$" " TFILE=$PWD/tfile"
 234 .RB "$" " echo \[aq]%A\[aq] > $TFILE " "      # Full name of the day of the week"
 235 .RB "$" " echo \[aq]%T\[aq] >> $TFILE" "      # Time (HH:MM:SS)"
 236 .RB "$" " echo \[aq]%F\[aq] >> $TFILE" "      # ISO date (YYYY\-MM\-DD)"
 237 .RB "$" " date"
 238 .RB "$" " export DATEMSK=$TFILE"
 239 .RB "$" " ./a.out Tuesday \[aq]2009\-12\-28\[aq] \[aq]12:22:33\[aq]"
 240 Sun Sep  7 06:03:36 CEST 2008
 241 Call 1 ("Tuesday") succeeded:
 242     tm_sec   = 36
 243     tm_min   = 3
 244     tm_hour  = 6
 245     tm_mday  = 9
 246     tm_mon   = 8
 247     tm_year  = 108
 248     tm_wday  = 2
 249     tm_yday  = 252
 250     tm_isdst = 1
 251 Call 2 ("2009\-12\-28") succeeded:
 252     tm_sec   = 36
 253     tm_min   = 3
 254     tm_hour  = 6
 255     tm_mday  = 28
 256     tm_mon   = 11
 257     tm_year  = 109
 258     tm_wday  = 1
 259     tm_yday  = 361
 260     tm_isdst = 0
 261 Call 3 ("12:22:33") succeeded:
 262     tm_sec   = 33
 263     tm_min   = 22
 264     tm_hour  = 12
 265     tm_mday  = 7
 266     tm_mon   = 8
 267     tm_year  = 108
 268     tm_wday  = 0
 269     tm_yday  = 250
 270     tm_isdst = 1
 271 .EE
 272 .in
 273 .SS Program source
 274 \&
 275 .\" SRC BEGIN (getdate.c)
 276 .EX
 277 #define _GNU_SOURCE
 278 #include <stdio.h>
 279 #include <stdlib.h>
 280 #include <time.h>
 281 \&
 282 int
 283 main(int argc, char *argv[])
 284 {
 285     struct tm *tmp;
 286 \&
 287     for (size_t j = 1; j < argc; j++) {
 288         tmp = getdate(argv[j]);
 289 \&
 290         if (tmp == NULL) {
 291             printf("Call %zu failed; getdate_err = %d\en",
 292                    j, getdate_err);
 293             continue;
 294         }
 295 \&
 296         printf("Call %zu (\e"%s\e") succeeded:\en", j, argv[j]);
 297         printf("    tm_sec   = %d\en", tmp\->tm_sec);
 298         printf("    tm_min   = %d\en", tmp\->tm_min);
 299         printf("    tm_hour  = %d\en", tmp\->tm_hour);
 300         printf("    tm_mday  = %d\en", tmp\->tm_mday);
 301         printf("    tm_mon   = %d\en", tmp\->tm_mon);
 302         printf("    tm_year  = %d\en", tmp\->tm_year);
 303         printf("    tm_wday  = %d\en", tmp\->tm_wday);
 304         printf("    tm_yday  = %d\en", tmp\->tm_yday);
 305         printf("    tm_isdst = %d\en", tmp\->tm_isdst);
 306     }
 307 \&
 308     exit(EXIT_SUCCESS);
 309 }
 310 .EE
 311 .\" SRC END
 312 .SH SEE ALSO
 313 .BR time (2),
 314 .BR localtime (3),
 315 .BR setlocale (3),
 316 .BR strftime (3),
 317 .BR strptime (3)