TIMERADD(3)               (2017-09-15)                TIMERADD(3)

     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 normal-
          ized 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).

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     TIMERADD(3)               (2017-09-15)                TIMERADD(3)

          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() implementa-
          tion, 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
          This page is part of release 5.10 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/.

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