mirror of https://github.com/mkerrisk/man-pages
94 lines
3.7 KiB
Plaintext
94 lines
3.7 KiB
Plaintext
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "SIGEMPTYSET" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" sigemptyset
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.SH NAME
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sigemptyset \- initialize and empty a signal set
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.SH SYNOPSIS
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.LP
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\fB#include <signal.h>
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.br
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.sp
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int sigemptyset(sigset_t *\fP\fIset\fP\fB); \fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIsigemptyset\fP() function initializes the signal set pointed
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to by \fIset\fP, such that all signals defined in
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IEEE\ Std\ 1003.1-2001 are excluded.
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.SH RETURN VALUE
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.LP
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Upon successful completion, \fIsigemptyset\fP() shall return 0; otherwise,
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it shall return -1 and set \fIerrno\fP to indicate
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the error.
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.SH ERRORS
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.LP
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No errors are defined.
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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None.
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.SH RATIONALE
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.LP
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The implementation of the \fIsigemptyset\fP() (or \fIsigfillset\fP())
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function
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could quite trivially clear (or set) all the bits in the signal set.
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Alternatively, it would be reasonable to initialize part of
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the structure, such as a version field, to permit binary-compatibility
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between releases where the size of the set varies. For such
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reasons, either \fIsigemptyset\fP() or \fIsigfillset\fP() must be
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called prior to any
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other use of the signal set, even if such use is read-only (for example,
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as an argument to \fIsigpending\fP()). This function is not intended
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for dynamic allocation.
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.LP
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The \fIsigfillset\fP() and \fIsigemptyset\fP() functions require that
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the resulting
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signal set include (or exclude) all the signals defined in this volume
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of IEEE\ Std\ 1003.1-2001. Although it is outside
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the scope of this volume of IEEE\ Std\ 1003.1-2001 to place this requirement
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on signals that are implemented as extensions,
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it is recommended that implementation-defined signals also be affected
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by these functions. However, there may be a good reason for
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a particular signal not to be affected. For example, blocking or ignoring
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an implementation-defined signal may have undesirable
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side effects, whereas the default action for that signal is harmless.
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In such a case, it would be preferable for such a signal to
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be excluded from the signal set returned by \fIsigfillset\fP().
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.LP
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In early proposals there was no distinction between invalid and unsupported
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signals (the names of optional signals that were not
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supported by an implementation were not defined by that implementation).
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The [EINVAL] error was thus specified as a required error
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for invalid signals. With that distinction, it is not necessary to
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require implementations of these functions to determine whether
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an optional signal is actually supported, as that could have a significant
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performance impact for little value. The error could
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have been required for invalid signals and optional for unsupported
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signals, but this seemed unnecessarily complex. Thus, the error
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is optional in both cases.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fISignal Concepts\fP , \fIsigaction\fP() , \fIsigaddset\fP() , \fIsigdelset\fP()
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, \fIsigfillset\fP() , \fIsigismember\fP() , \fIsigpending\fP() ,
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\fIsigprocmask\fP() , \fIsigsuspend\fP() , the Base Definitions volume
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of IEEE\ Std\ 1003.1-2001, \fI<signal.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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