1TIMERADD(3) Linux Programmer's Manual TIMERADD(3)
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6 timeradd, timersub, timercmp, timerclear, timerisset - timeval opera‐
7 tions
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10 #include <sys/time.h>
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12 void timeradd(struct timeval *a, struct timeval *b,
13 struct timeval *res);
14 void timersub(struct timeval *a, struct timeval *b,
15 struct timeval *res);
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17 void timerclear(struct timeval *tvp);
18 int timerisset(struct timeval *tvp);
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20 int timercmp(struct timeval *a, struct timeval *b, CMP);
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22 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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24 All functions shown above:
25 Since glibc 2.19:
26 _DEFAULT_SOURCE
27 Glibc 2.19 and earlier:
28 _BSD_SOURCE
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31 The macros are provided to operate on timeval structures, defined in
32 <sys/time.h> as:
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34 struct timeval {
35 time_t tv_sec; /* seconds */
36 suseconds_t tv_usec; /* microseconds */
37 };
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39 timeradd() adds the time values in a and b, and places the sum in the
40 timeval pointed to by res. The result is normalized such that
41 res->tv_usec has a value in the range 0 to 999,999.
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43 timersub() subtracts the time value in b from the time value in a, and
44 places the result in the timeval pointed to by res. The result is nor‐
45 malized such that res->tv_usec has a value in the range 0 to 999,999.
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47 timerclear() zeros out the timeval structure pointed to by tvp, so that
48 it represents the Epoch: 1970-01-01 00:00:00 +0000 (UTC).
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50 timerisset() returns true (nonzero) if either field of the timeval
51 structure pointed to by tvp contains a nonzero value.
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53 timercmp() compares the timer values in a and b using the comparison
54 operator CMP, and returns true (nonzero) or false (0) depending on the
55 result of the comparison. Some systems (but not Linux/glibc), have a
56 broken timercmp() implementation, in which CMP of >=, <=, and == do not
57 work; portable applications can instead use
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59 !timercmp(..., <)
60 !timercmp(..., >)
61 !timercmp(..., !=)
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64 timerisset() and timercmp() return true (nonzero) or false (0).
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67 No errors are defined.
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70 Not in POSIX.1. Present on most BSD derivatives.
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73 gettimeofday(2), time(7)
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76 This page is part of release 5.13 of the Linux man-pages project. A
77 description of the project, information about reporting bugs, and the
78 latest version of this page, can be found at
79 https://www.kernel.org/doc/man-pages/.
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83Linux 2021-03-22 TIMERADD(3)