NAME

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

LIBRARY

       Standard C library (libc, -lc)

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.

STANDARDS

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

SEE ALSO

       gettimeofday(2), time(7)