1SIGHOLD(3P) POSIX Programmer's Manual SIGHOLD(3P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
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12 sighold, sigignore, sigpause, sigrelse, sigset — signal management
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15 #include <signal.h>
16 int sighold(int sig);
18 int sigignore(int sig);
19 int sigpause(int sig);
20 int sigrelse(int sig);
21 void (*sigset(int sig, void (*disp)(int)))(int);
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24 Use of any of these functions is unspecified in a multi-threaded
25 process.
26 The sighold(), sigignore(), sigpause(), sigrelse(), and sigset() func‐
28 tions provide simplified signal management.
29 The sigset() function shall modify signal dispositions. The sig argu‐
31 ment specifies the signal, which may be any signal except SIGKILL and
32 SIGSTOP. The disp argument specifies the signal's disposition, which
33 may be SIG_DFL, SIG_IGN, or the address of a signal handler. If
34 sigset() is used, and disp is the address of a signal handler, the sys‐
35 tem shall add sig to the signal mask of the calling process before exe‐
36 cuting the signal handler; when the signal handler returns, the system
37 shall restore the signal mask of the calling process to its state prior
38 to the delivery of the signal. In addition, if sigset() is used, and
39 disp is equal to SIG_HOLD, sig shall be added to the signal mask of the
40 calling process and sig's disposition shall remain unchanged. If
41 sigset() is used, and disp is not equal to SIG_HOLD, sig shall be
42 removed from the signal mask of the calling process.
43 The sighold() function shall add sig to the signal mask of the calling
45 process.
46 The sigrelse() function shall remove sig from the signal mask of the
48 calling process.
49 The sigignore() function shall set the disposition of sig to SIG_IGN.
51 The sigpause() function shall remove sig from the signal mask of the
53 calling process and suspend the calling process until a signal is
54 received. The sigpause() function shall restore the signal mask of the
55 process to its original state before returning.
56 If the action for the SIGCHLD signal is set to SIG_IGN, child processes
58 of the calling processes shall not be transformed into zombie processes
59 when they terminate. If the calling process subsequently waits for its
60 children, and the process has no unwaited-for children that were trans‐
61 formed into zombie processes, it shall block until all of its children
62 terminate, and wait(), waitid(), and waitpid() shall fail and set errno
63 to [ECHILD].
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66 Upon successful completion, sigset() shall return SIG_HOLD if the sig‐
67 nal had been blocked and the signal's previous disposition if it had
68 not been blocked. Otherwise, SIG_ERR shall be returned and errno set to
69 indicate the error.
70 The sigpause() function shall suspend execution of the thread until a
72 signal is received, whereupon it shall return -1 and set errno to
73 [EINTR].
74 For all other functions, upon successful completion, 0 shall be
76 returned. Otherwise, -1 shall be returned and errno set to indicate
77 the error.
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80 These functions shall fail if:
81 EINVAL The sig argument is an illegal signal number.
83 The sigset() and sigignore() functions shall fail if:
85 EINVAL An attempt is made to catch a signal that cannot be caught, or
87 to ignore a signal that cannot be ignored.
88 The following sections are informative.
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92 None.
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95 The sigaction() function provides a more comprehensive and reliable
96 mechanism for controlling signals; new applications should use the
97 sigaction() function instead of the obsolescent sigset() function.
98 The sighold() function, in conjunction with sigrelse() or sigpause(),
100 may be used to establish critical regions of code that require the
101 delivery of a signal to be temporarily deferred. For broader portabil‐
102 ity, the pthread_sigmask() or sigprocmask() functions should be used
103 instead of the obsolescent sighold() and sigrelse() functions.
104 For broader portability, the sigsuspend() function should be used
106 instead of the obsolescent sigpause() function.
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109 Each of these historic functions has a direct analog in the other func‐
110 tions which are required to be per-thread and thread-safe (aside from
111 sigprocmask(), which is replaced by pthread_sigmask()). The sigset()
112 function can be implemented as a simple wrapper for sigaction(). The
113 sighold() function is equivalent to sigprocmask() or pthread_sigmask()
114 with SIG_BLOCK set. The sigignore() function is equivalent to sigac‐
115 tion() with SIG_IGN set. The sigpause() function is equivalent to sig‐
116 suspend(). The sigrelse() function is equivalent to sigprocmask() or
117 pthread_sigmask() with SIG_UNBLOCK set.
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120 These functions may be removed in a future version.
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123 Section 2.4, Signal Concepts, exec, pause(), pthread_sigmask(), sigac‐
124 tion(), signal(), sigsuspend(), wait(), waitid()
125 The Base Definitions volume of POSIX.1‐2017, <signal.h>
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129 Portions of this text are reprinted and reproduced in electronic form
130 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
131 table Operating System Interface (POSIX), The Open Group Base Specifi‐
132 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
133 Electrical and Electronics Engineers, Inc and The Open Group. In the
134 event of any discrepancy between this version and the original IEEE and
135 The Open Group Standard, the original IEEE and The Open Group Standard
136 is the referee document. The original Standard can be obtained online
137 at http://www.opengroup.org/unix/online.html .
138 Any typographical or formatting errors that appear in this page are
140 most likely to have been introduced during the conversion of the source
141 files to man page format. To report such errors, see https://www.ker‐
142 nel.org/doc/man-pages/reporting_bugs.html .
143IEEE/The Open Group 2017 SIGHOLD(3P)