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30 .\" @(#)sigprocmask.2 8.1 (Berkeley) 6/4/93
31 .\"
32 .Dd June 4, 1993
33 .Dt SIGPROCMASK 2
34 .Os
35 .Sh NAME
36 .Nm sigprocmask
37 .Nd manipulate current signal mask
38 .Sh LIBRARY
39 .Lb libc
40 .Sh SYNOPSIS
41 .In signal.h
42 .Ft int
43 .Fn sigprocmask "int how" "const sigset_t * restrict set" "sigset_t * restrict oset"
44 .Sh DESCRIPTION
45 The
46 .Fn sigprocmask
47 function examines and/or changes the current signal mask (those signals
48 that are blocked from delivery).
49 Signals are blocked if they are members of the current signal mask set.
50 .Pp
51 If
52 .Fa set
53 is not null, the action of
54 .Fn sigprocmask
55 depends on the value of the parameter
56 .Fa how .
57 The signal mask is changed as a function of the specified
58 .Fa set
59 and the current mask.
60 The function is specified by
61 .Fa how
62 using one of the following values:
63 .Bl -tag -width SIG_UNBLOCK
64 .It Dv SIG_BLOCK
65 The new mask is the union of the current mask and the specified
66 .Fa set .
67 .It Dv SIG_UNBLOCK
68 The new mask is the intersection of the current mask
69 and the complement of the specified
70 .Fa set .
71 .It Dv SIG_SETMASK
72 The current mask is replaced by the specified
73 .Fa set .
74 .El
75 .Pp
76 If
77 .Fa oset
78 is not null, it is set to
79 the previous value of the signal mask.
80 .Pp
81 When
82 .Fa set
83 is null,
84 the value of
85 .Ar how
86 is insignificant and the mask remains unset
87 providing a way to examine the signal mask without modification.
88 .Pp
89 The system
90 quietly disallows
91 .Dv SIGKILL
92 or
93 .Dv SIGSTOP
94 to be blocked.
95 .Sh RETURN VALUES
96 A 0 value indicates that the call succeeded.
97 A \-1 return value indicates an error occurred and
98 .Va errno
99 is set to indicate the reason.
100 .Sh ERRORS
101 The
102 .Fn sigprocmask
103 call will fail and the signal mask will be unchanged if one
104 of the following occurs:
105 .Bl -tag -width Er
106 .It Bq Er EINVAL
107 .Fa how
108 has a value other than those listed here.
109 .El
110 .Sh SEE ALSO
111 .Xr kill 2 ,
112 .Xr sigaction 2 ,
113 .Xr sigsuspend 2 ,
114 .Xr pthread_sigmask 3 ,
115 .Xr sigsetops 3 ,
116 .Xr signal 7
117 .Sh STANDARDS
118 The
119 .Fn sigprocmask
120 function conforms to
121 .St -p1003.1-90 .