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 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.1-2001.  Present on most BSD derivatives.

SEE ALSO

       gettimeofday(2), time(7)

COLOPHON

       This  page  is  part  of  release 3.54 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/.