timeradd(3)                Library Functions Manual                timeradd(3)

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
       None.

HISTORY
       BSD.

SEE ALSO
       gettimeofday(2), time(7)

Linux man-pages 6.7               2023-10-31                       timeradd(3)