annotate doc/ctime.texi @ 16464:2a3849cfe7b9

Tests for module 'modf-ieee'. * modules/modf-ieee-tests: New file. * tests/test-modf-ieee.c: New file.
author Bruno Haible <bruno@clisp.org>
date Sun, 26 Feb 2012 17:55:21 +0100
parents 8250f2777afc
children e542fd46ad6f
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1 @node ctime
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2 @section ctime
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3 @findex ctime
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4
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5 @c Copyright (C) 2005, 2009-2012 Free Software Foundation, Inc.
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7 @c Permission is granted to copy, distribute and/or modify this document
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8 @c under the terms of the GNU Free Documentation License, Version 1.3 or
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9 @c any later version published by the Free Software Foundation; with no
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10 @c Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
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11 @c Texts. A copy of the license is included in the ``GNU Free
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12 @c Documentation License'' file as part of this distribution.
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13
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14 The @code{ctime} function need not be reentrant, and consequently is
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15 not required to be thread safe. Implementations of @code{ctime}
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16 typically write the time stamp into static buffer. If two threads
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17 call @code{ctime} at roughly the same time, you might end up with the
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18 wrong date in one of the threads, or some undefined string. There is
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19 a re-entrant interface @code{ctime_r}, that take a pre-allocated
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20 buffer and length of the buffer, and return @code{NULL} on errors.
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21 The input buffer should be at least 26 bytes in size. The output
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22 string is locale-independent. However, years can have more than 4
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23 digits if @code{time_t} is sufficiently wide, so the length of the
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24 required output buffer is not easy to determine. Increasing the
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25 buffer size when @code{ctime_r} return @code{NULL} is not necessarily
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26 sufficient. The @code{NULL} return value could mean some other error
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27 condition, which will not go away by increasing the buffer size.
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29 A more flexible function is @code{strftime}. However, note that it is
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30 locale dependent.