view doc/ctime.texi @ 7139:adb21c293305

Add copyright notices to long-enough files that lack them, since otherwise the files aren't clearly free. Use the same notice that getdate.texi already uses. * doc/alloca-opt.texi: Add copyright notice. * doc/alloca.texi: Likewise. * doc/ctime.texi: Likewise. * doc/functions.texi: Likewise. * doc/gcd.texi: Likewise. * doc/gnulib-tool.texi: Likewise. * doc/inet_ntoa.texi: Likewise. * doc/visibility.texi: Likewise. Change copyright notice from LGPL 2 to GPL 2, since that's the standard form used in the gnulib repository. * lib/lock.c: LGPL -> GPL. * lib/lock.h: Likewise. * lib/strnlen1.c: Likewise. * lib/strnlen1.h: Likewise. * lib/tls.c: Likewise. * lib/tls.h: Likewise. * lib/tmpdir.c: Likewise. * tests/test-lock.c: Likewise. * tests/test-stdint.c: Likewise. * tests/test-tls.c: Likewise.
author Paul Eggert <>
date Mon, 14 Aug 2006 22:19:54 +0000
parents f194efd935e3
children d67664a4e01c
line wrap: on
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@node ctime
@section ctime
@findex ctime

@c Copyright (C) 2005 Free Software Foundation, Inc.

@c Permission is granted to copy, distribute and/or modify this document
@c under the terms of the GNU Free Documentation License, Version 1.2 or
@c any later version published by the Free Software Foundation; with no
@c Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
@c Texts.  A copy of the license is included in the ``GNU Free
@c Documentation License'' file as part of this distribution.

The @code{ctime} function need not be reentrant, and consequently is
not required to be thread safe.  Implementations of @code{ctime}
typically write the time stamp into static buffer.  If two threads
call @code{ctime} at roughly the same time, you might end up with the
wrong date in one of the threads, or some undefined string.  There is
a re-entrant interface @code{ctime_r}, that take a pre-allocated
buffer and length of the buffer, and return @code{NULL} on errors.
The input buffer should be at least 26 bytes in size.  The output
string is locale-independent.  However, years can have more than 4
digits if @code{time_t} is sufficiently wide, so the length of the
required output buffer is not easy to determine.  Increasing the
buffer size when @code{ctime_r} return @code{NULL} is not necessarily
sufficient. The @code{NULL} return value could mean some other error
condition, which will not go away by increasing the buffer size.

A more flexible function is @code{strftime}.  However, note that it is
locale dependent.