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51 lines
1.5 KiB
Groff
51 lines
1.5 KiB
Groff
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.\"
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.\" $Id: sigsetmask.2,v 1.1 1997/02/27 07:32:16 gdr Exp $
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.\"
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.TH SIGSETMASK 2 "19 January 1997" GNO "System Calls"
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.SH NAME
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.BR sigsetmask
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\- set signal mask
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.SH SYNOPSIS
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#include <signal.h>
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.sp 1
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long
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\fBsigsetmask\fR(long \fImask\fR);
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.br
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#define \fBsigmask\fR(\fIsignum\fR)
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.SH DESCRIPTION
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.BR sigsetmask
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is usually used to restore signal masks after modifications by
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.BR sigblock .
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The parameter mask is the absolute value to which the process signal
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mask will be set. (Compare to
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.BR sigblock ,
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which adds the argument to the set of blocked signals.)
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.LP
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If there are pending instances of signals which become unblocked by the
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.BR sigsetmask
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call, they are 'released' into the system signal queue and their 'pending'
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status is cleared. The system signal queue is maintained by the kernel
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null process, and is used in situations where signals could not normally
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be sent (such as in interrupt handlers).
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.LP
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.BR sigmask
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is a macro that can be used to calculate signal masks for
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.BR sigsetmask .
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It takes a signal number, as listed in
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.BR signal (2),
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as an argument and returns a mask corresponding to that signal.
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.SH "RETURN VALUE"
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The previous value of the signal mask is returned from
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.BR sigsetmask .
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.SH CAVEATS
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If somehow the process re-blocks a signal released by
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.BR sigsetmask
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before the system signal queue processes it, it will be blocked and marked
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as pending. This can happen if a signal handler makes a
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.BR sigblock
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call.
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.SH SEE ALSO
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.BR kill (2),
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.BR sigblock (2),
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.BR signal (2)
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