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sigemptyset.3p (4299B)

    

  1. '\" et
  2. .TH SIGEMPTYSET "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
  3. .\"
  4. .SH PROLOG
  5. This manual page is part of the POSIX Programmer's Manual.
  6. The Linux implementation of this interface may differ (consult
  7. the corresponding Linux manual page for details of Linux behavior),
  8. or the interface may not be implemented on Linux.
  9. .\"
  10. .SH NAME
  11. sigemptyset
  12. \(em initialize and empty a signal set
  13. .SH SYNOPSIS
  14. .LP
  15. .nf
  16. #include <signal.h>
  17. .P
  18. int sigemptyset(sigset_t *\fIset\fP);
  19. .fi
  20. .SH DESCRIPTION
  21. The
  22. \fIsigemptyset\fR()
  23. function initializes the signal set pointed to by
  24. .IR set ,
  25. such that all signals defined in POSIX.1\(hy2008 are excluded.
  26. .SH "RETURN VALUE"
  27. Upon successful completion,
  28. \fIsigemptyset\fR()
  29. shall return 0; otherwise, it shall return \-1 and set
  30. .IR errno
  31. to indicate the error.
  32. .SH ERRORS
  33. No errors are defined.
  34. .LP
  35. .IR "The following sections are informative."
  36. .SH EXAMPLES
  37. None.
  38. .SH "APPLICATION USAGE"
  39. None.
  40. .SH RATIONALE
  41. The implementation of the
  42. \fIsigemptyset\fR()
  43. (or
  44. \fIsigfillset\fR())
  45. function could quite trivially clear (or set) all the bits in the
  46. signal set. Alternatively, it would be reasonable to initialize part
  47. of the structure, such as a version field, to permit
  48. binary-compatibility between releases where the size of the set
  49. varies. For such reasons, either
  50. \fIsigemptyset\fR()
  51. or
  52. \fIsigfillset\fR()
  53. must be called prior to any other use of the signal set, even if such
  54. use is read-only (for example, as an argument to
  55. \fIsigpending\fR()).
  56. This function is not intended for dynamic allocation.
  57. .P
  58. The
  59. \fIsigfillset\fR()
  60. and
  61. \fIsigemptyset\fR()
  62. functions require that the resulting signal set include (or exclude)
  63. all the signals defined in this volume of POSIX.1\(hy2017. Although it is outside the scope of
  64. \&this volume of POSIX.1\(hy2017 to place this requirement on signals that are implemented as
  65. extensions, it is recommended that implementation-defined signals
  66. also be affected by these functions. However, there may be a good
  67. reason for a particular signal not to be affected. For example,
  68. blocking or ignoring an implementation-defined signal may have
  69. undesirable side-effects, whereas the default action for that signal is
  70. harmless. In such a case, it would be preferable for such a signal to
  71. be excluded from the signal set returned by
  72. \fIsigfillset\fR().
  73. .P
  74. In early proposals there was no distinction between invalid and
  75. unsupported signals (the names of optional signals that were not
  76. supported by an implementation were not defined by that
  77. implementation). The
  78. .BR [EINVAL] 
  79. error was thus specified as a required error for invalid signals. With
  80. that distinction, it is not necessary to require implementations of
  81. these functions to determine whether an optional signal is actually
  82. supported, as that could have a significant performance impact for
  83. little value. The error could have been required for invalid signals
  84. and optional for unsupported signals, but this seemed unnecessarily
  85. complex. Thus, the error is optional in both cases.
  86. .SH "FUTURE DIRECTIONS"
  87. None.
  88. .SH "SEE ALSO"
  89. .ad l
  90. .IR "Section 2.4" ", " "Signal Concepts",
  91. .IR "\fIpthread_sigmask\fR\^(\|)",
  92. .IR "\fIsigaction\fR\^(\|)",
  93. .IR "\fIsigaddset\fR\^(\|)",
  94. .IR "\fIsigdelset\fR\^(\|)",
  95. .IR "\fIsigfillset\fR\^(\|)",
  96. .IR "\fIsigismember\fR\^(\|)",
  97. .IR "\fIsigpending\fR\^(\|)",
  98. .IR "\fIsigsuspend\fR\^(\|)"
  99. .ad b
  100. .P
  101. The Base Definitions volume of POSIX.1\(hy2017,
  102. .IR "\fB<signal.h>\fP"
  103. .\"
  104. .SH COPYRIGHT
  105. Portions of this text are reprinted and reproduced in electronic form
  106. from IEEE Std 1003.1-2017, Standard for Information Technology
  107. -- Portable Operating System Interface (POSIX), The Open Group Base
  108. Specifications Issue 7, 2018 Edition,
  109. Copyright (C) 2018 by the Institute of
  110. Electrical and Electronics Engineers, Inc and The Open Group.
  111. In the event of any discrepancy between this version and the original IEEE and
  112. The Open Group Standard, the original IEEE and The Open Group Standard
  113. is the referee document. The original Standard can be obtained online at
  114. http://www.opengroup.org/unix/online.html .
  115. .PP
  116. Any typographical or formatting errors that appear
  117. in this page are most likely
  118. to have been introduced during the conversion of the source files to
  119. man page format. To report such errors, see
  120. https://www.kernel.org/doc/man-pages/reporting_bugs.html .