1SIGVEC(3) Linux Programmer's Manual SIGVEC(3)
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6 sigvec, sigblock, sigsetmask, siggetmask, sigmask - BSD signal API
7
9 #include <signal.h>
10 int sigvec(int sig, const struct sigvec *vec, struct sigvec *ovec);
12 int sigmask(int signum);
14 int sigblock(int mask);
16 int sigsetmask(int mask);
17 int siggetmask(void);
18 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
20 All functions shown above:
22 Since glibc 2.19:
23 _DEFAULT_SOURCE
24 Glibc 2.19 and earlier:
25 _BSD_SOURCE
26
28 These functions are provided in glibc as a compatibility interface for
29 programs that make use of the historical BSD signal API. This API is
30 obsolete: new applications should use the POSIX signal API (sigac‐
31 tion(2), sigprocmask(2), etc.).
32 The sigvec() function sets and/or gets the disposition of the signal
34 sig (like the POSIX sigaction(2)). If vec is not NULL, it points to a
35 sigvec structure that defines the new disposition for sig. If ovec is
36 not NULL, it points to a sigvec structure that is used to return the
37 previous disposition of sig. To obtain the current disposition of sig
38 without changing it, specify NULL for vec, and a non-null pointer for
39 ovec.
40 The dispositions for SIGKILL and SIGSTOP cannot be changed.
42 The sigvec structure has the following form:
44 struct sigvec {
46 void (*sv_handler)(int); /* Signal disposition */
47 int sv_mask; /* Signals to be blocked in handler */
48 int sv_flags; /* Flags */
49 };
50 The sv_handler field specifies the disposition of the signal, and is
52 either: the address of a signal handler function; SIG_DFL, meaning the
53 default disposition applies for the signal; or SIG_IGN, meaning that
54 the signal is ignored.
55 If sv_handler specifies the address of a signal handler, then sv_mask
57 specifies a mask of signals that are to be blocked while the handler is
58 executing. In addition, the signal for which the handler is invoked is
59 also blocked. Attempts to block SIGKILL or SIGSTOP are silently ig‐
60 nored.
61 If sv_handler specifies the address of a signal handler, then the
63 sv_flags field specifies flags controlling what happens when the han‐
64 dler is called. This field may contain zero or more of the following
65 flags:
66 SV_INTERRUPT
68 If the signal handler interrupts a blocking system call, then
69 upon return from the handler the system call is not restarted:
70 instead it fails with the error EINTR. If this flag is not
71 specified, then system calls are restarted by default.
72 SV_RESETHAND
74 Reset the disposition of the signal to the default before call‐
75 ing the signal handler. If this flag is not specified, then the
76 handler remains established until explicitly removed by a later
77 call to sigvec() or until the process performs an execve(2).
78 SV_ONSTACK
80 Handle the signal on the alternate signal stack (historically
81 established under BSD using the obsolete sigstack() function;
82 the POSIX replacement is sigaltstack(2)).
83 The sigmask() macro constructs and returns a "signal mask" for signum.
85 For example, we can initialize the vec.sv_mask field given to sigvec()
86 using code such as the following:
87 vec.sv_mask = sigmask(SIGQUIT) | sigmask(SIGABRT);
89 /* Block SIGQUIT and SIGABRT during
90 handler execution */
91 The sigblock() function adds the signals in mask to the process's sig‐
93 nal mask (like POSIX sigprocmask(SIG_BLOCK)), and returns the process's
94 previous signal mask. Attempts to block SIGKILL or SIGSTOP are
95 silently ignored.
96 The sigsetmask() function sets the process's signal mask to the value
98 given in mask (like POSIX sigprocmask(SIG_SETMASK)), and returns the
99 process's previous signal mask.
100 The siggetmask() function returns the process's current signal mask.
102 This call is equivalent to sigblock(0).
103
105 The sigvec() function returns 0 on success; on error, it returns -1 and
106 sets errno to indicate the error.
107 The sigblock() and sigsetmask() functions return the previous signal
109 mask.
110 The sigmask() macro returns the signal mask for signum.
112
114 See the ERRORS under sigaction(2) and sigprocmask(2).
115
117 Starting with version 2.21, the GNU C library no longer exports the
118 sigvec() function as part of the ABI. (To ensure backward compatibil‐
119 ity, the glibc symbol versioning scheme continues to export the inter‐
120 face to binaries linked against older versions of the library.)
121
123 For an explanation of the terms used in this section, see at‐
124 tributes(7).
125 ┌────────────────────────────────────────────┬───────────────┬─────────┐
127 │Interface │ Attribute │ Value │
128 ├────────────────────────────────────────────┼───────────────┼─────────┤
129 │sigvec(), sigmask(), sigblock(), │ Thread safety │ MT-Safe │
130 │sigsetmask(), siggetmask() │ │ │
131 └────────────────────────────────────────────┴───────────────┴─────────┘
132
134 All of these functions were in 4.3BSD, except siggetmask(), whose ori‐
135 gin is unclear. These functions are obsolete: do not use them in new
136 programs.
137
139 On 4.3BSD, the signal() function provided reliable semantics (as when
140 calling sigvec() with vec.sv_mask equal to 0). On System V, signal()
141 provides unreliable semantics. POSIX.1 leaves these aspects of sig‐
142 nal() unspecified. See signal(2) for further details.
143 In order to wait for a signal, BSD and System V both provided a func‐
145 tion named sigpause(3), but this function has a different argument on
146 the two systems. See sigpause(3) for details.
147
149 kill(2), pause(2), sigaction(2), signal(2), sigprocmask(2), raise(3),
150 sigpause(3), sigset(3), signal(7)
151
153 This page is part of release 5.13 of the Linux man-pages project. A
154 description of the project, information about reporting bugs, and the
155 latest version of this page, can be found at
156 https://www.kernel.org/doc/man-pages/.
157Linux 2021-03-22 SIGVEC(3)