AIX 4.3.3
I am trying to write a signal handler into a ksh shell script. I would like to capture the SIGTERM, SIGINT, and the SIGTSTP signals, print out a message to the terminal, and continue executing the script. I have found a way to block the signals:
#! /bin/ksh
SIGTERM=15
SIGINT=2... (2 Replies)
Hi,
I have an c++ application which uses the function fork and execvp().
The parent does not wait until the child ends. The parents just creates children and let them do their stuff.
You can see the parent program as a batch-manager.
I have added a SIGCHLD handler to the program:
void... (3 Replies)
Hey guys,
I am trying to write a little shell, and was writing a signal handler to handle SIGINT (I am using 'stty intr ^C' and using ctrl-C to give SIGINT).
I wrote this signal handler: void handle_sigint()
{
write(2,"handling sigint\n",16);
write(1,"\nshell% ",8);
}
... (4 Replies)
I have written a program to demonstrate a problem I have encountered when using BSD style asynchronous input using the O_ASYNC flag in conjunction with a real time interval timer sending regular SIGALRM signals to the program. The SIGIO handler obeys all safe practices, using only an atomic update... (8 Replies)
Is it ok to use exit() inside a signal handler?
I catch SIGUSR1 in a signal handler and I try to close a file and then exit. The result is inconsistent. Sometimes the process exit and sometimes it returns to the original state before the signal handler was invoked.
Perhaps exit is not legal in... (8 Replies)
Hi,
I have a daq program that runs in an infinite loop until it receives SIGINT. A handler catches the signal and sets a flag to stop the while loop. After the loop some things have to be cleaned up.
The problem is that I want my main while loop to wait until the next full second begins, to... (2 Replies)
Hi,
I have a problem with signal handler algorithm in linux. My code is hanging ( It is continuously looping inside the signal handler) . I am pasting my code here...
Please provide me some help regarding this. I googled many places and wrote this code.. but doesnt seem to be working without... (6 Replies)
I was working on some Perl code that does signal handling and I came across this one liner and wasn't sure what it was doing.
local $SIG{__DIE__} = sub {$! = 2; die $_;};
I think the first part of the anonymous subroutine is setting $! to 2, but I am not sure what the second part is doing. ... (1 Reply)
Hello,
I'm writing some serial(UART) handler but have stuck on few issues, maybe anyone can help to show me what I'm doing wrong.
Basically I'm intending to write serial RX signal handler.
Application receives defined packages of data over serial which contains header and payload. Handler... (3 Replies)
Discussion started by: Lauris_k
3 Replies
LEARN ABOUT MOJAVE
net::server::sig5.18
Net::Server::SIG(3) User Contributed Perl Documentation Net::Server::SIG(3)NAME
Net::Server::SIG - adpf - Safer signal handling
SYNOPSIS
use Net::Server::SIG qw(register_sig check_sigs);
use IO::Select ();
use POSIX qw(WNOHANG);
my $select = IO::Select->new();
register_sig(PIPE => 'IGNORE',
HUP => 'DEFAULT',
USR1 => sub { print "I got a SIG $_[0]
"; },
USR2 => sub { print "I got a SIG $_[0]
"; },
CHLD => sub { 1 while waitpid(-1, WNOHANG) > 0; },
);
# add some handles to the select
$select->add(*STDIN);
# loop forever trying to stay alive
while(1) {
# do a timeout to see if any signals got passed us
# while we were processing another signal
my @fh = $select->can_read(10);
my $key;
my $val;
# this is the handler for safe (fine under unsafe also)
if (check_sigs()) {
# or my @sigs = check_sigs();
next unless @fh;
}
my $handle = $fh[@fh];
# do something with the handle
}
DESCRIPTION
Signals prior in Perl prior to 5.7 were unsafe. Since then signals have been implemented in a more safe algorithm. Net::Server::SIG
provides backwards compatibility, while still working reliably with newer releases.
Using a property of the select() function, Net::Server::SIG attempts to fix the unsafe problem. If a process is blocking on select() any
signal will short circuit the select. Using this concept, Net::Server::SIG does the least work possible (changing one bit from 0 to 1).
And depends upon the actual processing of the signals to take place immediately after the the select call via the "check_sigs" function.
See the example shown above and also see the sigtest.pl script located in the examples directory of this distribution.
FUNCTIONS
"register_sig($SIG => &code_ref)"
Takes key/value pairs where the key is the signal name, and the argument is either a code ref, or the words 'DEFAULT' or 'IGNORE'. The
function register_sig must be used in conjunction with check_sigs, and with a blocking select() function call -- otherwise, you will
observe the registered signal mysteriously vanish.
"unregister_sig($SIG)"
Takes the name of a signal as an argument. Calls register_sig with a this signal name and 'DEFAULT' as arguments (same as
register_sig(SIG,'DEFAULT')
"check_sigs()"
Checks to see if any registered signals have occured. If so, it will play the registered code ref for that signal. Return value is
array containing any SIGNAL names that had occured.
"sig_is_registered($SIG)"
Takes a signal name and returns any registered code_ref for that signal.
AUTHORS
Paul Seamons (paul@seamons.com)
Rob B Brown (rob@roobik.com) - Provided a sounding board and feedback in creating Net::Server::SIG and sigtest.pl.
LICENSE
This package may be distributed under the terms of either the
GNU General Public License
or the
Perl Artistic License
All rights reserved.
perl v5.18.2 2013-01-09 Net::Server::SIG(3)