mirror of https://github.com/mkerrisk/man-pages
124 lines
3.9 KiB
Plaintext
124 lines
3.9 KiB
Plaintext
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "MKTIME" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" mktime
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.SH NAME
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mktime \- convert broken-down time into time since the Epoch
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.SH SYNOPSIS
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.LP
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\fB#include <time.h>
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.br
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.sp
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time_t mktime(struct tm *\fP\fItimeptr\fP\fB);
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fImktime\fP() function shall convert the broken-down time, expressed
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as local time, in the structure pointed to by
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\fItimeptr\fP, into a time since the Epoch value with the same encoding
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as that of the values returned by \fItime\fP(). The original values
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of the \fItm_wday\fP and \fItm_yday\fP components of the
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structure are ignored, and the original values of the other components
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are not restricted to the ranges described in \fI<time.h>\fP.
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.LP
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A
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positive or 0 value for \fItm_isdst\fP shall cause \fImktime\fP()
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to presume initially that Daylight Savings Time, respectively,
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is or is not in effect for the specified time. A negative value for
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\fItm_isdst\fP shall cause \fImktime\fP() to attempt to
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determine whether Daylight Savings Time is in effect for the specified
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time.
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.LP
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Local timezone information shall be set as though \fImktime\fP() called
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\fItzset\fP().
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.LP
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The relationship between the \fBtm\fP structure (defined in the \fI<time.h>\fP
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header) and the time in seconds since the Epoch is that the result
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shall be as specified in the expression given in the definition
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of seconds since the Epoch (see the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
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Section 4.14, Seconds Since the Epoch) corrected for timezone and
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any seasonal time
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adjustments, where the names in the structure and in the expression
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correspond.
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.LP
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Upon successful completion, the values of the \fItm_wday\fP and \fItm_yday\fP
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components of the structure shall be set
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appropriately, and the other components are set to represent the specified
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time since the Epoch, but with their values forced to
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the ranges indicated in the \fI<time.h>\fP entry; the final value
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of \fItm_mday\fP
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shall not be set until \fItm_mon\fP and \fItm_year\fP are determined.
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.SH RETURN VALUE
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.LP
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The \fImktime\fP() function shall return the specified time since
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the Epoch encoded as a value of type \fBtime_t\fP. If the
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time since the Epoch cannot be represented, the function shall return
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the value (\fBtime_t\fP)-1.
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.SH ERRORS
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.LP
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No errors are defined.
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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What day of the week is July 4, 2001?
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.sp
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.RS
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.nf
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\fB#include <stdio.h>
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#include <time.h>
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.sp
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struct tm time_str;
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.sp
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char daybuf[20];
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.sp
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int main(void)
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{
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time_str.tm_year = 2001 - 1900;
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time_str.tm_mon = 7 - 1;
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time_str.tm_mday = 4;
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time_str.tm_hour = 0;
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time_str.tm_min = 0;
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time_str.tm_sec = 1;
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time_str.tm_isdst = -1;
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if (mktime(&time_str) == -1)
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(void)puts("-unknown-");
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else {
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(void)strftime(daybuf, sizeof(daybuf), "%A", &time_str);
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(void)puts(daybuf);
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}
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return 0;
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}
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\fP
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.fi
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.RE
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.SH APPLICATION USAGE
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.LP
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None.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIasctime\fP() , \fIclock\fP() , \fIctime\fP()
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, \fIdifftime\fP() , \fIgmtime\fP() , \fIlocaltime\fP() , \fIstrftime\fP()
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, \fIstrptime\fP() , \fItime\fP() , \fIutime\fP() , the Base
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Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<time.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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