01-24-2002
See the sigaction() system call man page. The easiest way to do this is create signal handling routines in your code that are called when signals are received. Most, but not all, signals can be caught and handled. Off the top of my head, the few that can't be handled are SIGKILL and SIGSTOP in both single and multi-threaded applications, and SIGWAITING, SIGCANCEL, and SIGLWP in multi-threaded applications.
A good book covering signals and other advanced UNIX programming topics is
Advanced Programming in the UNIX Environment
by W. Richard Stevens
ISBN 0201563177
You can find it on amazon at
http://www.amazon.com/exec/obidos/AS...209275-1145405
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send(n) Tk Built-In Commands send(n)
__________________________________________________________________________________________________________________________________________________
NAME
send - Execute a command in a different application
SYNOPSIS
send ?options? app cmd ?arg arg ...?
_________________________________________________________________
DESCRIPTION
This command arranges for cmd (and args) to be executed in the application named by app. It returns the result or error from that command
execution. App may be the name of any application whose main window is on the display containing the sender's main window; it need not be
within the same process. If no arg arguments are present, then the command to be executed is contained entirely within the cmd argument.
If one or more args are present, they are concatenated to form the command to be executed, just as for the eval command.
If the initial arguments of the command begin with ``-'' they are treated as options. The following options are currently defined:
-async Requests asynchronous invocation. In this case the send command will complete immediately without waiting for cmd to complete in
the target application; no result will be available and errors in the sent command will be ignored. If the target application is
in the same process as the sending application then the -async option is ignored.
-displayof pathName
Specifies that the target application's main window is on the display of the window given by pathName, instead of the display con-
taining the application's main window.
-- Serves no purpose except to terminate the list of options. This option is needed only if app could contain a leading ``-'' charac-
ter.
APPLICATION NAMES
The name of an application is set initially from the name of the program or script that created the application. You can query and change
the name of an application with the tk appname command.
DISABLING SENDS
If the send command is removed from an application (e.g. with the command rename send {}) then the application will not respond to incom-
ing send requests anymore, nor will it be able to issue outgoing requests. Communication can be reenabled by invoking the tk appname com-
mand.
SECURITY
The send command is potentially a serious security loophole. On Unix, any application that can connect to your X server can send scripts to
your applications. These incoming scripts can use Tcl to read and write your files and invoke subprocesses under your name. Host-based
access control such as that provided by xhost is particularly insecure, since it allows anyone with an account on particular hosts to con-
nect to your server, and if disabled it allows anyone anywhere to connect to your server. In order to provide at least a small amount of
security, Tk checks the access control being used by the server and rejects incoming sends unless (a) xhost-style access control is enabled
(i.e. only certain hosts can establish connections) and (b) the list of enabled hosts is empty. This means that applications cannot con-
nect to your server unless they use some other form of authorization such as that provide by xauth. Under Windows, send is currently dis- |
abled. Most of the functionality is provided by the dde command instead.
KEYWORDS
application, dde, name, remote execution, security, send |
Tk 4.0 send(n)