mirror of https://github.com/mkerrisk/man-pages
106 lines
2.9 KiB
Groff
106 lines
2.9 KiB
Groff
.\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.TH TIMEGM 3 2016-12-12 "GNU" "Linux Programmer's Manual"
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.SH NAME
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timegm, timelocal \- inverses of gmtime and localtime
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.SH SYNOPSIS
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.nf
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.B #include <time.h>
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.PP
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.BI "time_t timelocal(struct tm *" tm );
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.PP
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.BI "time_t timegm(struct tm *" tm );
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.PP
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.fi
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.PP
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.BR timelocal (),
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.BR timegm ():
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Since glibc 2.19:
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_DEFAULT_SOURCE
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Glibc 2.19 and earlier:
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_BSD_SOURCE || _SVID_SOURCE
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.SH DESCRIPTION
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The functions
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.BR timelocal ()
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and
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.BR timegm ()
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are the inverses of
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.BR localtime (3)
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and
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.BR gmtime (3).
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Both functions take a broken-down time and convert it to calendar time
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(seconds since the Epoch, 1970-01-01 00:00:00 +0000, UTC).
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The difference between the two functions is that
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.BR timelocal ()
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takes the local timezone into account when doing the conversion, while
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.BR timegm ()
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takes the input value to be Coordinated Universal Time (UTC).
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.SH RETURN VALUE
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On success,
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these functions return the calendar time (seconds since the Epoch),
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expressed as a value of type
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.IR time_t .
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On error, they return the value
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.I (time_t)\ \-1
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and set
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.I errno
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to indicate the cause of the error.
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.SH ERRORS
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.TP
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.B EOVERFLOW
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The result cannot be represented.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lbw21 lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR timelocal (),
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.BR timegm ()
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T} Thread safety MT-Safe env locale
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.TE
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.SH CONFORMING TO
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These functions are nonstandard GNU extensions
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that are also present on the BSDs.
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Avoid their use.
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.SH NOTES
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The
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.BR timelocal ()
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function is equivalent to the POSIX standard function
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.BR mktime (3).
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There is no reason to ever use it.
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.SH SEE ALSO
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.BR gmtime (3),
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.BR localtime (3),
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.BR mktime (3),
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.BR tzset (3)
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