C<raise()>, i.e. it doesn't send a signal to the identified process
like it does on Unix platforms. Instead it immediately calls
C<TerminateProcess(process,signal)>. Thus the signal argument is
-used to set the exit-status of the terminated process. This behavior
-may change in future.
+used to set the exit-status of the terminated process. In particular,
+C<kill(0,$pid)> will kill the process identified by C<$pid> (unlike
+on Unix). This behavior may change in future.
=item *
=head2 How do I timeout a slow event?
Use the alarm() function, probably in conjunction with a signal
-handler, as documented L<perlipc/"Signals"> and chapter 6 of the
+handler, as documented in L<perlipc/"Signals"> and chapter 6 of the
Camel. You may instead use the more flexible Sys::AlarmCall module
available from CPAN.
See also C<each>, C<values> and C<sort>.
-=item kill LIST
+=item kill SIGNAL, LIST
-Sends a signal to a list of processes. The first element of
-the list must be the signal to send. Returns the number of
+Sends a signal to a list of processes. Returns the number of
processes successfully signaled (which is not necessarily the
same as the number actually killed).
$cnt = kill 1, $child1, $child2;
kill 9, @goners;
-Unlike in the shell, in Perl if the I<SIGNAL> is negative, it kills
+If SIGNAL is zero, no signal is sent to the process. This is a
+useful way to check that the process is alive and hasn't changed
+its UID. See L<perlport> for notes on the portability of this
+construct.
+
+Unlike in the shell, if SIGNAL is negative, it kills
process groups instead of processes. (On System V, a negative I<PROCESS>
number will also kill process groups, but that's not portable.) That
means you usually want to use positive not negative signals. You may also
Although these are grouped by family, they all have the precedence
of assignment.
-Unlike in C, the assignment operator produces a valid lvalue. Modifying
-an assignment is equivalent to doing the assignment and then modifying
-the variable that was assigned to. This is useful for modifying
-a copy of something, like this:
+Unlike in C, the scalar assignment operator produces a valid lvalue.
+Modifying an assignment is equivalent to doing the assignment and
+then modifying the variable that was assigned to. This is useful
+for modifying a copy of something, like this:
($tmp = $global) =~ tr [A-Z] [a-z];
$a += 2;
$a *= 3;
+Similarly, a list assignment in list context produces the list of
+lvalues assigned to, and a list assignment in scalar context returns
+the number of elements produced by the expression on the right hand
+side of the assignment.
+
=head2 Comma Operator
Binary "," is the comma operator. In scalar context it evaluates
Available only for socket handles. (S<RISC OS>)
-=item kill LIST
+=item kill SIGNAL, LIST
Not implemented, hence not useful for taint checking. (S<Mac OS>,
S<RISC OS>)
-Available only for process handles returned by the C<system(1, ...)>
-method of spawning a process. (Win32)
+Unlike Unix platforms, C<kill(0, $pid)> will actually terminate
+the process. (Win32)
=item link OLDFILE,NEWFILE
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