mirror of https://github.com/mkerrisk/man-pages
153 lines
3.7 KiB
Groff
153 lines
3.7 KiB
Groff
.\" Copyright (c) 2007 by Michael Kerrisk <mtk.manpages@gmail.com>
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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.\" manual page may be incorrect or out-of-date.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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.\" 2007-07-31, mtk, Created
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.\"
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.TH TIMERADD 3 2010-02-25 "Linux" "Linux Programmer's Manual"
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.SH NAME
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timeradd, timersub, timercmp, timerclear, timerisset \- timeval operations
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.SH SYNOPSIS
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.nf
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.B #include <sys/time.h>
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.BI "void timeradd(struct timeval *" a ", struct timeval *" b ,
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.BI " struct timeval *" res );
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.BI "void timersub(struct timeval *" a ", struct timeval *" b ,
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.BI " struct timeval *" res );
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.BI "void timerclear(struct timeval *" tvp );
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.BI "int timerisset(struct timeval *" tvp );
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.BI "int timercmp(struct timeval *" a ", struct timeval *" b ", " CMP );
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.fi
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.sp
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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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.sp
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All functions shown above:
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_BSD_SOURCE
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.SH DESCRIPTION
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The macros are provided to operate on
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.I timeval
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structures, defined in
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.I <sys/time.h>
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as:
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.sp
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.in +4n
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.nf
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struct timeval {
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time_t tv_sec; /* seconds */
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suseconds_t tv_usec; /* microseconds */
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};
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.fi
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.in
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.PP
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.BR timeradd ()
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adds the time values in
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.I a
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and
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.IR b ,
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and places the sum in the
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.I timeval
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pointed to by
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.IR res .
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The result is normalized such that
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.I res\->tv_usec
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has a value in the range 0 to 999,999.
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.BR timersub ()
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subtracts the time value in
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.I b
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from the time value in
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.IR a ,
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and places the result in the
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.I timeval
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pointed to by
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.IR res .
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The result is normalized such that
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.I res\->tv_usec
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has a value in the range 0 to 999,999.
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.BR timerclear ()
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zeros out the
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.I timeval
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structure pointed to by
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.IR tvp ,
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so that it represents the Epoch: 1970-01-01 00:00:00 +0000 (UTC).
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.BR timerisset ()
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returns true (nonzero) if either field of the
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.I timeval
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structure pointed to by
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.I tvp
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contains a nonzero value.
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.BR timercmp ()
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compares the timer values in
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.I a
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and
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.I b
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using the comparison operator
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.IR CMP ,
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and returns true (nonzero) or false (0) depending on
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the result of the comparison.
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Some systems (but not Linux/glibc),
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have a broken
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.BR timercmp ()
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implementation,
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.\" HP-UX, Tru64, Irix have a definition like:
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.\"#define timercmp(tvp, uvp, cmp) \
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.\" ((tvp)->tv_sec cmp (uvp)->tv_sec || \
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.\" (tvp)->tv_sec == (uvp)->tv_sec && (tvp)->tv_usec cmp (uvp)->tv_usec)
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in which
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.I CMP
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of
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.IR >= ,
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.IR <= ,
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and
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.I ==
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do not work;
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portable applications can instead use
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!timercmp(..., <)
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!timercmp(..., >)
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!timercmp(..., !=)
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.SH RETURN VALUE
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.BR timerisset ()
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and
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.BR timercmp ()
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return true (nonzero) or false (0).
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.SH ERRORS
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No errors are defined.
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.SH CONFORMING TO
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Not in POSIX.1.
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Present on most BSD derivatives.
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.SH SEE ALSO
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.BR gettimeofday (2),
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.BR time (7)
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