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:
           Since glibc 2.19:
               _DEFAULT_SOURCE
           Glibc 2.19 and earlier:
               _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
       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 (nonzero) or false (0).

ERRORS

       No errors are defined.

CONFORMING TO

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

SEE ALSO

       gettimeofday(2), time(7)

COLOPHON

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