timerisset(3)

1timeradd(3)                Library Functions Manual                timeradd(3)
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NAME

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

10       Standard C library (libc, -lc)
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SYNOPSIS

13       #include <sys/time.h>
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15       void timeradd(struct timeval *a, struct timeval *b,
16                     struct timeval *res);
17       void timersub(struct timeval *a, struct timeval *b,
18                     struct timeval *res);
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20       void timerclear(struct timeval *tvp);
21       int timerisset(struct timeval *tvp);
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23       int timercmp(struct timeval *a, struct timeval *b, CMP);
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25   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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27       All functions shown above:
28           Since glibc 2.19:
29               _DEFAULT_SOURCE
30           glibc 2.19 and earlier:
31               _BSD_SOURCE
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DESCRIPTION

34       The macros are provided to operate on timeval  structures,  defined  in
35       <sys/time.h> as:
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37           struct timeval {
38               time_t      tv_sec;     /* seconds */
39               suseconds_t tv_usec;    /* microseconds */
40           };
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42       timeradd()  adds  the time values in a and b, and places the sum in the
43       timeval pointed  to  by  res.   The  result  is  normalized  such  that
44       res->tv_usec has a value in the range 0 to 999,999.
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46       timersub()  subtracts the time value in b from the time value in a, and
47       places the result in the timeval pointed to by res.  The result is nor‐
48       malized such that res->tv_usec has a value in the range 0 to 999,999.
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50       timerclear() zeros out the timeval structure pointed to by tvp, so that
51       it represents the Epoch: 1970-01-01 00:00:00 +0000 (UTC).
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53       timerisset() returns true (nonzero) if  either  field  of  the  timeval
54       structure pointed to by tvp contains a nonzero value.
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56       timercmp()  compares  the  timer values in a and b using the comparison
57       operator CMP, and returns true (nonzero) or false (0) depending on  the
58       result  of  the comparison.  Some systems (but not Linux/glibc), have a
59       broken timercmp() implementation, in which CMP of >=, <=, and == do not
60       work; portable applications can instead use
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62           !timercmp(..., <)
63           !timercmp(..., >)
64           !timercmp(..., !=)
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RETURN VALUE

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

70       No errors are defined.
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STANDARDS

73       None.
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HISTORY

76       BSD.
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