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timerisset.3

TIMERADD

Section: Linux Programmer's Manual (3)
Updated: 2009-02-26
Index Return to Main Contents
 

NAME

timeradd, timersub, timercmp, timerclear, timerisset - timeval operations  

SYNOPSIS

#include <sys/time.h>

void timeradd(struct timeval *a, struct timeval *b,
              struct timeval *res);

void timersub(struct timeval *a, struct timeval *b,
              struct timeval *res);

void timerclear(struct timeval *tvp);

int timerisset(struct timeval *tvp);

int timercmp(struct timeval *a, struct timeval *b, CMP);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

All functions shown above: _BSD_SOURCE  

DESCRIPTION

The macros are provided to operate on timeval structures, defined in <sys/time.h> as:

struct timeval {
    time_t      tv_sec;     /* seconds */
    suseconds_t tv_usec;    /* microseconds */
};

timeradd() adds the time values in a and b, and places the sum in the timeval pointed to by res. The result is normalized such that res->tv_usec has a value in the range 0 to 999,999.

timersub() subtracts the time value in b from the time value in a, and places the result in the timeval pointed to by res. The result is normalized such that res->tv_usec has a value in the range 0 to 999,999.

timerclear() zeros out the timeval structure pointed to by tvp, so that it represents the time at midnight on the morning of 1 January 1970 (the Epoch).

timerisset() returns true (non-zero) if either field of the timeval structure pointed to by tvp contains a non-zero value.

timercmp() compares the timer values in a and b using the comparison operator CMP, and returns true (non-zero) or false (0) depending on the result of the comparison. Some systems (but not Linux/glibc), have a broken timercmp() implementation, in which CMP of >=, <=, and == do not work; portable applications can instead use


    !timercmp(..., <)
    !timercmp(..., >)
    !timercmp(..., !=)  

RETURN VALUE

timerisset() and timercmp() return true (non-zero) or false (0).  

ERRORS

No errors are defined.  

CONFORMING TO

Not in POSIX.1-2001. Present on most BSD derivatives.  

SEE ALSO

gettimeofday(2), time(7)  

COLOPHON

This page is part of release 3.21 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/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
SEE ALSO
COLOPHON

 

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