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timeradd(3) — Linux manual page

timeradd(3)              Library Functions Manualtimeradd(3)

NAME        top

       timeradd, timersub, timercmp, timerclear, timerisset - timeval       operations

LIBRARY        top

       Standard C library (libc,-lc)

SYNOPSIS        top

#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_SOURCE

DESCRIPTION        top

       The macros are provided to operate ontimeval structures, defined       in<sys/time.h> as:           struct timeval {               time_t      tv_sec;     /* seconds */               suseconds_t tv_usec;    /* microseconds */           };timeradd() adds the time values ina andb, and places the sum in       thetimeval pointed to byres.  The result is normalized such thatres->tv_usec has a value in the range 0 to 999,999.timersub() subtracts the time value inb from the time value ina,       and places the result in thetimeval pointed to byres.  The       result is normalized such thatres->tv_usec has a value in the       range 0 to 999,999.timerclear() zeros out thetimeval structure pointed to bytvp, so       that it represents the Epoch: 1970-01-01 00:00:00 +0000 (UTC).timerisset() returns true (nonzero) if either field of thetimeval       structure pointed to bytvp contains a nonzero value.timercmp() compares the timer values ina andb using the       comparison operatorCMP, and returns true (nonzero) or false (0)       depending on the result of the comparison.  Some systems (but not       Linux/glibc), have a brokentimercmp() implementation, in whichCMP of>=,<=, and== do not work; portable applications can       instead use           !timercmp(..., <)           !timercmp(..., >)           !timercmp(..., !=)

RETURN VALUE        top

timerisset() andtimercmp() return true (nonzero) or false (0).

ERRORS        top

       No errors are defined.

STANDARDS        top

       None.

HISTORY        top

       BSD.

SEE ALSO        top

gettimeofday(2),time(7)

COLOPHON        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17timeradd(3)

Pages that refer to this page:gettimeofday(2), timeval(3type), time(7)

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