TIMERADD(3)                         Linux Programmer's Manual                         TIMERADD(3)



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
       Epoch: 1970-01-01 00:00:00 +0000 (UTC).

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

       timercmp()  compares  the  timer  values in a and b using the comparison operator CMP, and
       returns true (nonzero) or false (0) depending on the result of the comparison.  Some  sys‐
       tems  (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 (nonzero) 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 3.74 of the Linux 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/.



Linux                                       2010-02-25                                TIMERADD(3)