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timegm(3) [debian man page]

TIMEGM(3)						     Linux Programmer's Manual							 TIMEGM(3)

NAME
timegm, timelocal - inverses of gmtime and localtime SYNOPSIS
#include <time.h> time_t timelocal(struct tm *tm); time_t timegm(struct tm *tm); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): timelocal(), timegm(): _BSD_SOURCE || _SVID_SOURCE DESCRIPTION
The functions timelocal() and timegm() are the inverses of localtime(3) and gmtime(3). CONFORMING TO
These functions are nonstandard GNU extensions that are also present on the BSDs. Avoid their use; see NOTES. NOTES
The timelocal() function is equivalent to the POSIX standard function mktime(3). There is no reason to ever use it. For a portable version of timegm(), set the TZ environment variable to UTC, call mktime(3) and restore the value of TZ. Something like #include <time.h> #include <stdlib.h> time_t my_timegm(struct tm *tm) { time_t ret; char *tz; tz = getenv("TZ"); setenv("TZ", "", 1); tzset(); ret = mktime(tm); if (tz) setenv("TZ", tz, 1); else unsetenv("TZ"); tzset(); return ret; } SEE ALSO
gmtime(3), localtime(3), mktime(3), tzset(3) COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. GNU
2007-07-26 TIMEGM(3)

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TIMEGM(3)						     Linux Programmer's Manual							 TIMEGM(3)

NAME
timegm, timelocal - inverses of gmtime and localtime SYNOPSIS
#include <time.h> time_t timelocal(struct tm *tm); time_t timegm(struct tm *tm); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): timelocal(), timegm(): Since glibc 2.19: _DEFAULT_SOURCE Glibc 2.19 and earlier: _BSD_SOURCE || _SVID_SOURCE DESCRIPTION
The functions timelocal() and timegm() are the inverses of localtime(3) and gmtime(3). Both functions take a broken-down time and convert it to calendar time (seconds since the Epoch, 1970-01-01 00:00:00 +0000, UTC). The difference between the two functions is that timelo- cal() takes the local timezone into account when doing the conversion, while timegm() takes the input value to be Coordinated Universal Time (UTC). RETURN VALUE
On success, these functions return the calendar time (seconds since the Epoch), expressed as a value of type time_t. On error, they return the value (time_t) -1 and set errno to indicate the cause of the error. ERRORS
EOVERFLOW The result cannot be represented. ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). +----------------------+---------------+--------------------+ |Interface | Attribute | Value | +----------------------+---------------+--------------------+ |timelocal(), timegm() | Thread safety | MT-Safe env locale | +----------------------+---------------+--------------------+ CONFORMING TO
These functions are nonstandard GNU extensions that are also present on the BSDs. Avoid their use. NOTES
The timelocal() function is equivalent to the POSIX standard function mktime(3). There is no reason to ever use it. SEE ALSO
gmtime(3), localtime(3), mktime(3), tzset(3) COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. GNU
2016-12-12 TIMEGM(3)

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