Differences between current version and revision by previous author of SIGHUP.
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Newer page: | version 11 | Last edited on Saturday, July 23, 2005 1:23:41 pm | by AristotlePagaltzis | |
Older page: | version 10 | Last edited on Wednesday, June 15, 2005 11:31:49 pm | by MichaelJager | Revert |
@@ -1,15 +1,25 @@
-!!!Signal: Hangup
+!!! Signal: Hangup
-This signal is generated by the kernel
when your controlling terminal goes away to the terminals ProcessGroup.
Or, in simplier terms, when you close the Xterm, or hang up a modem. Since daemons run in the background and don't have a controlling terminal, they often use SIGHUP to signal that they should reread their configuration files. This can cause issues with some programs that work as both a daemon and an interactive program, such as fetchmail(1).
-An example of a daemon that rereads it's
configuration file on SIGHUP is init(8), the first process created (which is responsible for creating all other processes, like getty for logging in). If you edit /etc/
inittab, its configuration file, you can do
+This signal is generated by the [Kernel]
when your controlling terminal goes away to the terminals ProcessGroup. Or, in simplier terms, when you close the Xterm, or hang up a modem. Since daemons run in the background and don't have a controlling terminal, they often use [
SIGHUP]
to signal that they should reread their configuration files. This can cause issues with some programs that work as both a daemon and an interactive program, such as fetchmail(1).
+
+An example of a daemon that rereads its
configuration file on [
SIGHUP]
is init(8), the first process created (which is responsible for creating all other processes, like getty for logging in). If you edit inittab(5)
, its configuration file, you can do
+
+ <verbatim>
kill -HUP 1
+ </verbatim>
+
and it will re-read the config file (note that the correct way to do this is to use [telinit(8)]).
-To restart an inetd(8) service, you find inetd's ProcessId
and send a hangup
to it:
- kill -HUP {
inetd_pid}
+To restart an inetd(8) service, you find its [PID]
and send a [SIGHUP]
to it:
+
+ <verbatim>
+ kill -HUP $
inetd_pid
+ </verbatim>
+
+You can prevent a process from recieving a [SIGHUP] signal by using the command nohup(1), for example:
-You can prevent a process from recieving a SIGHUP signal by using the command
nohup(1)
+ <verbatim>
+
nohup wget http://www.example.com/ &
+ </verbatim>
-For example:
- nohup wget http://www.example.com/ &
-
will run "
wget" that is not attached to a
terminal (and therefore doesn
't recieve a SIGHUP)
when you disconnect.
This is useful if the file you are downloading
is long, but
you want to logout before the download
is complete.
The "
&" at the end
is used
to put the command into the background.
+will run wget(1) detached from the
terminal, so it won
't recieve a [
SIGHUP]
when you disconnect. This is useful if a download
is so large that
you want to log out instead of waiting until it
is complete. (
The <tt>
&</tt>
is [Shell] lingo
to put the command into the background so that you can do something else, such as, uh, logging out
.)