The <sys/select.h> header shall define the timeval structure
that includes at least the following
members:
time_t tv_sec Seconds.
suseconds_t tv_usec Microseconds.
The time_t and suseconds_t types shall be defined as described
in <sys/types.h> .
The sigset_t type shall be defined as described in <signal.h>
.
The timespec structure shall be defined as described in <time.h>
.
The <sys/select.h> header shall define the fd_set type
as a structure.
Each of the following may be declared as a function, or defined as
a macro, or both:
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void FD_CLR(int fd, fd_set *fdset)
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Clears the bit for the file descriptor fd in the file descriptor
set fdset.
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int FD_ISSET(int fd, fd_set *fdset)
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Returns a non-zero value if the bit for the file descriptor fd
is set in the file descriptor set by fdset, and 0
otherwise.
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void FD_SET(int fd, fd_set *fdset)
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Sets the bit for the file descriptor fd in the file descriptor
set fdset.
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void FD_ZERO(fd_set *fdset)
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Initializes the file descriptor set fdset to have zero bits
for all file descriptors.
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If implemented as macros, these may evaluate their arguments more
than once, so applications should ensure that the arguments
they supply are never expressions with side effects.
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The following shall be defined as a macro:
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FD_SETSIZE
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Maximum number of file descriptors in an fd_set structure.
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The following shall be declared as functions and may also be defined
as macros. Function prototypes shall be provided.
int pselect(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
const struct timespec *restrict, const sigset_t *restrict);
int select(int, fd_set *restrict, fd_set *restrict, fd_set *restrict,
struct timeval *restrict);
Inclusion of the <sys/select.h> header may make visible all
symbols from the headers <signal.h>, <sys/time.h>,
and <time.h>.
The following sections are informative.
<signal.h> , <sys/time.h> ,
<sys/types.h> , <time.h> , the
System Interfaces volume of IEEE Std 1003.1-2001, pselect(),
select()
