mirror of https://github.com/mkerrisk/man-pages
113 lines
3.6 KiB
Plaintext
113 lines
3.6 KiB
Plaintext
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "CTIME" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" ctime
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.SH NAME
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ctime, ctime_r \- convert a time value to a date and time string
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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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char *ctime(const time_t *\fP\fIclock\fP\fB);
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.br
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\fP
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.LP
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\fBchar *ctime_r(const time_t *\fP\fIclock\fP\fB, char *\fP\fIbuf\fP\fB);
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\fP
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\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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For \fIctime\fP(): The functionality described on this reference
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page is aligned with the ISO\ C standard. Any
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conflict between the requirements described here and the ISO\ C standard
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is unintentional. This volume of
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IEEE\ Std\ 1003.1-2001 defers to the ISO\ C standard.
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.LP
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The \fIctime\fP() function shall convert the time pointed to by \fIclock\fP,
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representing time in seconds since the Epoch, to
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local time in the form of a string. It shall be equivalent to:
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.sp
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.RS
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.nf
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\fBasctime(localtime(clock))
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\fP
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.fi
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.RE
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.LP
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The
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\fIasctime\fP(), \fIctime\fP(), \fIgmtime\fP(),
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and \fIlocaltime\fP() functions shall return values in one of two
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static objects: a
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broken-down time structure and an array of \fBchar\fP. Execution of
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any of the functions may overwrite the information returned in
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either of these objects by any of the other functions.
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.LP
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The \fIctime\fP() function need not be reentrant. A function that
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is not required to be reentrant is not required to be
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thread-safe.
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.LP
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The \fIctime_r\fP() function shall convert the calendar time pointed
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to by \fIclock\fP to local time in exactly the same form as
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\fIctime\fP() and put the string into the array pointed to by \fIbuf\fP
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(which shall be at least 26 bytes in size) and return
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\fIbuf\fP.
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.LP
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Unlike \fIctime\fP(), the thread-safe version \fIctime_r\fP() is not
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required to set \fItzname\fP.
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.SH RETURN VALUE
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.LP
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The \fIctime\fP() function shall return the pointer returned by \fIasctime\fP()
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with
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that broken-down time as an argument.
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.LP
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Upon successful completion, \fIctime_r\fP() shall return a pointer
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to the string pointed to by \fIbuf\fP. When an error is
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encountered, a null pointer shall be returned.
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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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None.
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.SH APPLICATION USAGE
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.LP
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Values for the broken-down time structure can be obtained by calling
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\fIgmtime\fP() or
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\fIlocaltime\fP(). The \fIctime\fP() function is included for compatibility
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with older
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implementations, and does not support localized date and time formats.
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Applications should use the \fIstrftime\fP() function to achieve maximum
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portability.
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.LP
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The \fIctime_r\fP() function is thread-safe and shall return values
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in a user-supplied buffer instead of possibly using a
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static data area that may be overwritten by each call.
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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() , \fIdifftime\fP() , \fIgmtime\fP()
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, \fIlocaltime\fP()
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, \fImktime\fP() , \fIstrftime\fP() , \fIstrptime\fP() , \fItime\fP()
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, \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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