1TIMERADD(3)                Linux Programmer's Manual               TIMERADD(3)
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NAME

6       timeradd,  timersub,  timercmp, timerclear, timerisset - timeval opera‐
7       tions
8

SYNOPSIS

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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DESCRIPTION

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
58
59           !timercmp(..., <)
60           !timercmp(..., >)
61           !timercmp(..., !=)
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RETURN VALUE

64       timerisset() and timercmp() return true (nonzero) or false (0).
65

ERRORS

67       No errors are defined.
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CONFORMING TO

70       Not in POSIX.1.  Present on most BSD derivatives.
71

SEE ALSO

73       gettimeofday(2), time(7)
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COLOPHON

76       This  page  is  part of release 5.12 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)
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