bsd/man/man2/sigprocmask.2

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