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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