Adding to Perderabo's comment on using newer semantics of signal handling instead of older semantics.
Using signal function, while executing the code block within the signal handler there is no guarantee that another signal of the same type delivered would be handled the same way; instead the second signal of the same type delivered would default to its default action which in most of the cases would be to terminate.
for example:
when its at the " this instruction point " and if a signal is again delivered at this point, proper house keeping operations intended for the signal handler will not be completed.
But this never happens with the newer semantics with sigaction,
when the code instructions are executed within the signal action block kernel guarantees that it will not deliver the same signal type until the signal action block is completed.
so with the newer semantics you are guaranteed that your house keeping operations are done.
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)
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)
I have a problem with signal handlers not working.
I have a long 1000 line code and somehow this code for signal handling is not working:
$SIG{INT} = \&interrupt;
sub interrupt {
print STDERR "Caught a control c!\n";
exit; # or just about anything else you'd want to do
}
Any... (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 DEBIAN
bsd_signal
BSD_SIGNAL(3) Linux Programmer's Manual BSD_SIGNAL(3)NAME
bsd_signal - signal handling with BSD semantics
SYNOPSIS
#define _XOPEN_SOURCE /* See feature_test_macros(7) */
#include <signal.h>
typedef void (*sighandler_t)(int);
sighandler_t bsd_signal(int signum, sighandler_t handler);
DESCRIPTION
The bsd_signal() function takes the same arguments, and performs the same task, as signal(2).
The difference between the two is that bsd_signal() is guaranteed to provide reliable signal semantics, that is: a) the disposition of the
signal is not reset to the default when the handler is invoked; b) delivery of further instances of the signal is blocked while the signal
handler is executing; and c) if the handler interrupts a blocking system call, then the system call is automatically restarted. A portable
application cannot rely on signal(2) to provide these guarantees.
RETURN VALUE
The bsd_signal() function returns the previous value of the signal handler, or SIG_ERR on error.
ERRORS
As for signal(2).
CONFORMING TO
4.2BSD, POSIX.1-2001. POSIX.1-2008 removes the specification of bsd_signal(), recommending the use of sigaction(2) instead.
NOTES
Use of bsd_signal() should be avoided; use sigaction(2) instead.
On modern Linux systems, bsd_signal() and signal(2) are equivalent. But on older systems, signal(2) provided unreliable signal semantics;
see signal(2) for details.
The use of sighandler_t is a GNU extension; this type is only defined if the _GNU_SOURCE feature test macro is defined.
SEE ALSO sigaction(2), signal(2), sysv_signal(3), signal(7)COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
2009-03-15 BSD_SIGNAL(3)