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TIMERADD(3) Linux Programmer's Manual TIMERADD(3)

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

#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

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(..., !=)

timerisset() and timercmp() return true (nonzero) or false (0).

No errors are defined.

Not in POSIX.1. Present on most BSD derivatives.

gettimeofday(2), time(7)

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2017-09-15 Linux