+++ /dev/null
-.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
-.\"
-.\" %%%LICENSE_START(VERBATIM)
-.\" Permission is granted to make and distribute verbatim copies of this
-.\" manual provided the copyright notice and this permission notice are
-.\" preserved on all copies.
-.\"
-.\" Permission is granted to copy and distribute modified versions of this
-.\" manual under the conditions for verbatim copying, provided that the
-.\" entire resulting derived work is distributed under the terms of a
-.\" permission notice identical to this one.
-.\"
-.\" Since the Linux kernel and libraries are constantly changing, this
-.\" manual page may be incorrect or out-of-date. The author(s) assume no
-.\" responsibility for errors or omissions, or for damages resulting from
-.\" the use of the information contained herein. The author(s) may not
-.\" have taken the same level of care in the production of this manual,
-.\" which is licensed free of charge, as they might when working
-.\" professionally.
-.\"
-.\" Formatted or processed versions of this manual, if unaccompanied by
-.\" the source, must acknowledge the copyright and authors of this work.
-.\" %%%LICENSE_END
-.\"
-.\" References consulted:
-.\" Linux libc source code
-.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
-.\" 386BSD man pages
-.\" Modified Sat Jul 24 19:49:27 1993 by Rik Faith (faith@cs.unc.edu)
-.\" Modified Fri Apr 26 12:38:55 MET DST 1996 by Martin Schulze (joey@linux.de)
-.\" Modified 2001-11-13, aeb
-.\" Modified 2001-12-13, joey, aeb
-.\" Modified 2004-11-16, mtk
-.\"
-.TH CTIME 3 2014-08-19 "" "Linux Programmer's Manual"
-.SH NAME
-asctime, ctime, gmtime, localtime, mktime, asctime_r, ctime_r, gmtime_r,
-localtime_r \- transform date and time to broken-down time or ASCII
-.SH SYNOPSIS
-.nf
-.B #include <time.h>
-.sp
-.BI "char *asctime(const struct tm *" tm );
-.br
-.BI "char *asctime_r(const struct tm *" tm ", char *" buf );
-.sp
-.BI "char *ctime(const time_t *" timep );
-.br
-.BI "char *ctime_r(const time_t *" timep ", char *" buf );
-.sp
-.BI "struct tm *gmtime(const time_t *" timep );
-.br
-.BI "struct tm *gmtime_r(const time_t *" timep ", struct tm *" result );
-.sp
-.BI "struct tm *localtime(const time_t *" timep );
-.br
-.BI "struct tm *localtime_r(const time_t *" timep ", struct tm *" result );
-.sp
-.BI "time_t mktime(struct tm *" tm );
-.fi
-.sp
-.in -4n
-Feature Test Macro Requirements for glibc (see
-.BR feature_test_macros (7)):
-.in
-.ad l
-.sp
-.BR asctime_r (),
-.BR ctime_r (),
-.BR gmtime_r (),
-.BR localtime_r ():
-.RS
-_POSIX_C_SOURCE\ >=\ 1 || _XOPEN_SOURCE || _BSD_SOURCE ||
-_SVID_SOURCE || _POSIX_SOURCE
-.RE
-.ad
-.SH DESCRIPTION
-The
-.BR ctime (),
-.BR gmtime ()
-and
-.BR localtime ()
-functions all take
-an argument of data type \fItime_t\fP, which represents calendar time.
-When interpreted as an absolute time value, it represents the number of
-seconds elapsed since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
-.PP
-The
-.BR asctime ()
-and
-.BR mktime ()
-functions both take an argument
-representing broken-down time, which is a representation
-separated into year, month, day, and so on.
-.PP
-Broken-down time is stored
-in the structure \fItm\fP, which is defined in \fI<time.h>\fP as follows:
-.sp
-.in +4n
-.nf
-struct tm {
- int tm_sec; /* Seconds (0-60) */
- int tm_min; /* Minutes (0-59) */
- int tm_hour; /* Hours (0-23) */
- int tm_mday; /* Day of the month (1-31) */
- int tm_mon; /* Month (0-11) */
- int tm_year; /* Year - 1900 */
- int tm_wday; /* Day of the week (0-6, Sunday = 0) */
- int tm_yday; /* Day in the year (0-365, 1 Jan = 0) */
- int tm_isdst; /* Daylight saving time */
-};
-.fi
-.in
-.PP
-The members of the \fItm\fP structure are:
-.TP 10
-.I tm_sec
-The number of seconds after the minute, normally in the range 0 to 59,
-but can be up to 60 to allow for leap seconds.
-.TP
-.I tm_min
-The number of minutes after the hour, in the range 0 to 59.
-.TP
-.I tm_hour
-The number of hours past midnight, in the range 0 to 23.
-.TP
-.I tm_mday
-The day of the month, in the range 1 to 31.
-.TP
-.I tm_mon
-The number of months since January, in the range 0 to 11.
-.TP
-.I tm_year
-The number of years since 1900.
-.TP
-.I tm_wday
-The number of days since Sunday, in the range 0 to 6.
-.TP
-.I tm_yday
-The number of days since January 1, in the range 0 to 365.
-.TP
-.I tm_isdst
-A flag that indicates whether daylight saving time is in effect at the
-time described.
-The value is positive if daylight saving time is in
-effect, zero if it is not, and negative if the information is not
-available.
-.PP
-The call
-.BI ctime( t )
-is equivalent to
-.BI asctime(localtime( t )) \fR.
-It converts the calendar time \fIt\fP into a
-null-terminated string of the form
-.sp
-.RS
-"Wed Jun 30 21:49:08 1993\\n"
-.RE
-.sp
-The abbreviations for the days of the week are "Sun", "Mon", "Tue", "Wed",
-"Thu", "Fri", and "Sat".
-The abbreviations for the months are "Jan",
-"Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", and
-"Dec".
-The return value points to a statically allocated string which
-might be overwritten by subsequent calls to any of the date and time
-functions.
-The function also sets the external
-variables \fItzname\fP, \fItimezone\fP, and \fIdaylight\fP (see
-.BR tzset (3))
-with information about the current timezone.
-The reentrant version
-.BR ctime_r ()
-does the same, but stores the
-string in a user-supplied buffer
-which should have room for at least 26 bytes.
-It need not
-set \fItzname\fP, \fItimezone\fP, and \fIdaylight\fP.
-.PP
-The
-.BR gmtime ()
-function converts the calendar time \fItimep\fP to
-broken-down time representation, expressed in Coordinated Universal Time
-(UTC).
-It may return NULL when the year does not fit into an integer.
-The return value points to a statically allocated struct which might be
-overwritten by subsequent calls to any of the date and time functions.
-The
-.BR gmtime_r ()
-function does the same, but stores the data in a
-user-supplied struct.
-.PP
-The
-.BR localtime ()
-function converts the calendar time \fItimep\fP to
-broken-down time representation,
-expressed relative to the user's specified timezone.
-The function acts as if it called
-.BR tzset (3)
-and sets the external variables \fItzname\fP with
-information about the current timezone, \fItimezone\fP with the difference
-between Coordinated Universal Time (UTC) and local standard time in
-seconds, and \fIdaylight\fP to a nonzero value if daylight savings
-time rules apply during some part of the year.
-The return value points to a statically allocated struct which might be
-overwritten by subsequent calls to any of the date and time functions.
-The
-.BR localtime_r ()
-function does the same, but stores the data in a
-user-supplied struct.
-It need not set \fItzname\fP, \fItimezone\fP, and \fIdaylight\fP.
-.PP
-The
-.BR asctime ()
-function converts the broken-down time value
-\fItm\fP into a null-terminated string with the same format as
-.BR ctime ().
-The return value points to a statically allocated string which might be
-overwritten by subsequent calls to any of the date and time functions.
-The
-.BR asctime_r ()
-function does the same, but stores the string in
-a user-supplied buffer which should have room for at least 26 bytes.
-.PP
-The
-.BR mktime ()
-function converts a broken-down time structure, expressed
-as local time, to calendar time representation.
-The function ignores
-the values supplied by the caller in the
-.I tm_wday
-and
-.I tm_yday
-fields.
-The value specified in the
-.I tm_isdst
-field informs
-.BR mktime ()
-whether or not daylight saving time (DST)
-is in effect for the time supplied in the
-.I tm
-structure:
-a positive value means DST is in effect;
-zero means that DST is not in effect;
-and a negative value means that
-.BR mktime ()
-should (use timezone information and system databases to)
-attempt to determine whether DST is in effect at the specified time.
-
-The
-.BR mktime ()
-function modifies the fields of the
-.IR tm
-structure as follows:
-.I tm_wday
-and
-.I tm_yday
-are set to values determined from the contents of the other fields;
-if structure members are outside their valid interval, they will be
-normalized (so that, for example, 40 October is changed into 9 November);
-.I tm_isdst
-is set (regardless of its initial value)
-to a positive value or to 0, respectively,
-to indicate whether DST is or is not in effect at the specified time.
-Calling
-.BR mktime ()
-also sets the external variable \fItzname\fP with
-information about the current timezone.
-
-If the specified broken-down
-time cannot be represented as calendar time (seconds since the Epoch),
-.BR mktime ()
-returns
-.I (time_t)\ \-1
-and does not alter the
-members of the broken-down time structure.
-.SH RETURN VALUE
-Each of these functions returns the value described, or NULL
-(\-1 in case of
-.BR mktime ())
-in case an error was detected.
-.SH CONFORMING TO
-POSIX.1-2001.
-C89 and C99 specify
-.BR asctime (),
-.BR ctime (),
-.BR gmtime (),
-.BR localtime (),
-and
-.BR mktime ().
-POSIX.1-2008 marks
-.BR asctime (),
-.BR asctime_r (),
-.BR ctime (),
-and
-.BR ctime_r ()
-as obsolete,
-recommending the use of
-.BR strftime (3)
-instead.
-.SH NOTES
-The four functions
-.BR asctime (),
-.BR ctime (),
-.BR gmtime ()
-and
-.BR localtime ()
-return a pointer to static data and hence are not thread-safe.
-The thread-safe versions,
-.BR asctime_r (),
-.BR ctime_r (),
-.BR gmtime_r ()
-and
-.BR localtime_r (),
-are specified by SUSv2.
-
-POSIX.1-2001 says:
-"The
-.BR asctime (),
-.BR ctime (),
-.BR gmtime (),
-and
-.BR localtime ()
-functions shall return values in one of two static objects:
-a broken-down time structure and an array of type
-.IR char .
-Execution of any of the functions may overwrite the information returned
-in either of these objects by any of the other functions."
-This can occur in the glibc implementation.
-.LP
-In many implementations, including glibc, a 0 in
-.I tm_mday
-is interpreted as meaning the last day of the preceding month.
-.LP
-The glibc version of \fIstruct tm\fP has additional fields
-.sp
-.RS
-.nf
-long tm_gmtoff; /* Seconds east of UTC */
-const char *tm_zone; /* Timezone abbreviation */
-.fi
-.RE
-.sp
-defined when
-.B _BSD_SOURCE
-was set before including
-.IR <time.h> .
-This is a BSD extension, present in 4.3BSD-Reno.
-
-According to POSIX.1-2004,
-.BR localtime ()
-is required to behave as though
-.BR tzset (3)
-was called, while
-.BR localtime_r ()
-does not have this requirement.
-.\" See http://thread.gmane.org/gmane.comp.time.tz/2034/
-For portable code,
-.BR tzset (3)
-should be called before
-.BR localtime_r ().
-.SH SEE ALSO
-.BR date (1),
-.BR gettimeofday (2),
-.BR time (2),
-.BR utime (2),
-.BR clock (3),
-.BR difftime (3),
-.BR strftime (3),
-.BR strptime (3),
-.BR timegm (3),
-.BR tzset (3),
-.BR time (7)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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