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TIMERADD(3)                Linux Programmer's ManualTIMERADD(3)NAME       timeradd,  timersub,  timercmp, timerclear, timerisset - timeval opera-       tionsSYNOPSIS       #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 (seefeature_test_macros(7)):       All functions shown above:           Since glibc 2.19:               _DEFAULT_SOURCE           Glibc 2.19 and earlier:               _BSD_SOURCEDESCRIPTION       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 nor-       malized 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 ALSOgettimeofday(2),time(7)COLOPHON       This  page  is  part of release 5.05 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       https://www.kernel.org/doc/man-pages/.Linux                             2017-09-15TIMERADD(3)