1SIGSET(3) Linux Programmer's Manual SIGSET(3)
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6 sigset, sighold, sigrelse, sigignore - System V signal API
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9 #define _XOPEN_SOURCE 500
10 #include <signal.h>
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12 typedef void (*sighandler_t)(int);
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14 sighandler_t sigset(int sig, sighandler_t disp);
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16 int sighold(int sig);
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18 int sigrelse(int sig);
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20 int sigignore(int sig);
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23 These functions are provided in glibc as a compatibility interface for
24 programs that make use of the historical System V signal API. This API
25 is obsolete: new applications should use the POSIX signal API (sigac‐
26 tion(2), sigprocmask(2), etc.)
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28 The sigset() function modifies the disposition of the signal sig. The
29 disp argument can be the address of a signal handler function, or one
30 of the following constants:
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32 SIG_DFL
33 Reset the disposition of sig to the default.
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35 SIG_IGN
36 Ignore sig.
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38 SIG_HOLD
39 Add sig to the process's signal mask, but leave the disposition
40 of sig unchanged.
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42 If disp specifies the address of a signal handler, then sig is added to
43 the process's signal mask during execution of the handler.
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45 If disp was specified as a value other than SIG_HOLD, then sig is
46 removed from the process's signal mask.
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48 The dispositions for SIGKILL and SIGSTOP cannot be changed.
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50 The sighold() function adds sig to the calling process's signal mask.
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52 The sigrelse() function removes sig from the calling process's signal
53 mask.
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55 The sigignore() function sets the disposition of sig to SIG_IGN.
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58 On success, sigset() returns SIG_HOLD if sig was blocked before the
59 call, or the signal's previous disposition if it was not blocked before
60 the call. On error, sigset() returns -1, with errno set to indicate
61 the error. (But see BUGS below.)
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63 The sighold(), sigrelse(), and sigignore() functions return 0 on suc‐
64 cess; on error, these functions return -1 and set errno to indicate the
65 error.
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68 For sigset() see the ERRORS under sigaction(2) and sigprocmask(2).
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70 For sighold() and sigrelse() see the ERRORS under sigprocmask(2).
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72 For sigignore(), see the errors under sigaction(2).
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75 SVr4, POSIX.1-2001. These functions are obsolete: do not use them in
76 new programs. POSIX.1-2008 marks sighold(), sigignore(), sigpause(),
77 sigrelse(), and sigset() as obsolete, recommending the use of sigac‐
78 tion(2), sigprocmask(2), pthread_sigmask(3), and sigsuspend(2) instead.
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81 These functions appeared in glibc version 2.1.
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83 The sighandler_t type is a GNU extension; it is only used on this page
84 to make the sigset() prototype more easily readable.
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86 The sigset() function provides reliable signal handling semantics (as
87 when calling sigaction(2) with sa_mask equal to 0).
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89 On System V, the signal() function provides unreliable semantics (as
90 when calling sigaction(2) with sa_mask equal to SA_RESETHAND | SA_NODE‐
91 FER). On BSD, signal() provides reliable semantics. POSIX.1-2001
92 leaves these aspects of signal() unspecified. See signal(2) for fur‐
93 ther details.
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95 In order to wait for a signal, BSD and System V both provided a func‐
96 tion named sigpause(3), but this function has a different argument on
97 the two systems. See sigpause(3) for details.
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100 In versions of glibc before 2.2, sigset() did not unblock sig if disp
101 was specified as a value other than SIG_HOLD.
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103 In versions of glibc before 2.5, sigset() does not correctly return the
104 previous disposition of the signal in two cases. First, if disp is
105 specified as SIG_HOLD, then a successful sigset() always returns
106 SIG_HOLD. Instead, it should return the previous disposition of the
107 signal (unless the signal was blocked, in which case SIG_HOLD should be
108 returned). Second, if the signal is currently blocked, then the return
109 value of a successful sigset() should be SIG_HOLD. Instead, the previ‐
110 ous disposition of the signal is returned. These problems have been
111 fixed since glibc 2.5.
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114 kill(2), pause(2), sigaction(2), signal(2), sigprocmask(2), raise(3),
115 sigpause(3), sigvec(3), feature_test_macros(7), signal(7)
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118 This page is part of release 3.22 of the Linux man-pages project. A
119 description of the project, and information about reporting bugs, can
120 be found at http://www.kernel.org/doc/man-pages/.
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124Linux 2009-03-15 SIGSET(3)