freebsd-dev/lib/libc/sys/sigprocmask.2

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.\" Copyright (c) 1983, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" @(#)sigprocmask.2 8.1 (Berkeley) 6/4/93
1999-08-28 00:22:10 +00:00
.\" $FreeBSD$
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.\"
.Dd May 7, 2010
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.Dt SIGPROCMASK 2
.Os
.Sh NAME
.Nm sigprocmask
.Nd manipulate current signal mask
.Sh LIBRARY
.Lb libc
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.Sh SYNOPSIS
.In signal.h
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.Ft int
.Fo sigprocmask
.Fa "int how"
.Fa "const sigset_t * restrict set"
.Fa "sigset_t * restrict oset"
.Fc
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.Sh DESCRIPTION
The
.Fn sigprocmask
system call examines and/or changes the current signal mask (those signals
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that are blocked from delivery).
Signals are blocked if they are members of the current signal mask set.
.Pp
If
.Fa set
is not null, the action of
.Fn sigprocmask
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depends on the value of the
.Fa how
argument.
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The signal mask is changed as a function of the specified
.Fa set
and the current mask.
The function is specified by
.Fa how
using one of the following values from
.In signal.h :
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.Bl -tag -width SIG_UNBLOCK
.It Dv SIG_BLOCK
The new mask is the union of the current mask and the specified
.Fa set .
.It Dv SIG_UNBLOCK
The new mask is the intersection of the current mask
and the complement of the specified
.Fa set .
.It Dv SIG_SETMASK
The current mask is replaced by the specified
.Fa set .
.El
.Pp
If
.Fa oset
is not null, it is set to
the previous value of the signal mask.
When
.Fa set
is null,
the value of
.Fa how
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is insignificant and the mask remains unset
providing a way to examine the signal mask without modification.
.Pp
The system
quietly disallows
.Dv SIGKILL
or
.Dv SIGSTOP
to be blocked.
.Pp
In threaded applications,
.Xr pthread_sigmask 3
must be used instead of
.Fn sigprocmask .
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.Sh RETURN VALUES
.Rv -std sigprocmask
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.Sh ERRORS
The
.Fn sigprocmask
system call will fail and the signal mask will be unchanged if one
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of the following occurs:
.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa how
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argument
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has a value other than those listed here.
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.El
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.Sh SEE ALSO
.Xr kill 2 ,
.Xr sigaction 2 ,
.Xr sigpending 2 ,
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.Xr sigsuspend 2 ,
.Xr fpsetmask 3 ,
.Xr pthread_sigmask 3 ,
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.Xr sigsetops 3
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.Sh STANDARDS
The
.Fn sigprocmask
system call is expected to
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conform to
.St -p1003.1-90 .