this is a script, the name is test.sh
#!/bin/bash
cleanup(){
echo "Caught SIGINT ..."
exit 1
}
trap 'cleanup' 3
while :;do
echo "a"
sleep 3
done
if I run nohup ./test.sh & in linux bash directly , it can catch kill -3 PID signal ,
but if I write nohup ./test.sh & in a script file that name is go.sh) ,and I run go.sh , an then test.sh can't catch kill -3 PID signal
how can I write the go.sh script to make sure test.sh catch -3 signal ?
kill -3 (SIGQUIT) would not work. According to bash's manual:
When bash is interactive, in the absence of any traps, it ignores SIGTERM (so that kill 0 does not kill an interactive shell), and SIGINT is caught and handled (so that the wait builtin is interruptible). In all cases, bash ignores SIGQUIT. If job control is in effect, bash ignores SIGTTIN, SIGTTOU, and SIGTSTP.
Related
I have a script ./runStart.sh that creates a new xterm and in this xterm launch the script run.log command.
Then, to finish the process I launch a script ./runStop.sh that kills the xterm and do other stuff behind.
The problem I have is that as I kill the process while running, there is no exit call, so the script command does not save the data in the actual file.
Do you know how I could launch a command in the second script ./runStop.sh that makes this exit call instead of the kill <pid> command ?
You can use the bash builtin trap to catch a signal (except KILL and STOP) and do the required cleanup.
For example, here i am catching the pseudo signal EXIT that would cover any signal that would make the shell to exit:
xterm -e '/bin/bash' -c 'trap "echo ok >/tmp/foobar" EXIT; sleep 5'
sleep 5 is my main task and echo ok >/tmp/foobar is cleanup task upon exiting.
Alternately if are sure about the signal to be sent/received e.g. HUP, INT, you can trap those directly.
How can you suppress the Terminated message that comes up after you kill a
process in a bash script?
I tried set +bm, but that doesn't work.
I know another solution involves calling exec 2> /dev/null, but is that
reliable? How do I reset it back so that I can continue to see stderr?
In order to silence the message, you must be redirecting stderr at the time the message is generated. Because the kill command sends a signal and doesn't wait for the target process to respond, redirecting stderr of the kill command does you no good. The bash builtin wait was made specifically for this purpose.
Here is very simple example that kills the most recent background command. (Learn more about $! here.)
kill $!
wait $! 2>/dev/null
Because both kill and wait accept multiple pids, you can also do batch kills. Here is an example that kills all background processes (of the current process/script of course).
kill $(jobs -rp)
wait $(jobs -rp) 2>/dev/null
I was led here from bash: silently kill background function process.
The short answer is that you can't. Bash always prints the status of foreground jobs. The monitoring flag only applies for background jobs, and only for interactive shells, not scripts.
see notify_of_job_status() in jobs.c.
As you say, you can redirect so standard error is pointing to /dev/null but then you miss any other error messages. You can make it temporary by doing the redirection in a subshell which runs the script. This leaves the original environment alone.
(script 2> /dev/null)
which will lose all error messages, but just from that script, not from anything else run in that shell.
You can save and restore standard error, by redirecting a new filedescriptor to point there:
exec 3>&2 # 3 is now a copy of 2
exec 2> /dev/null # 2 now points to /dev/null
script # run script with redirected stderr
exec 2>&3 # restore stderr to saved
exec 3>&- # close saved version
But I wouldn't recommend this -- the only upside from the first one is that it saves a sub-shell invocation, while being more complicated and, possibly even altering the behavior of the script, if the script alters file descriptors.
EDIT:
For more appropriate answer check answer given by Mark Edgar
Solution: use SIGINT (works only in non-interactive shells)
Demo:
cat > silent.sh <<"EOF"
sleep 100 &
kill -INT $!
sleep 1
EOF
sh silent.sh
http://thread.gmane.org/gmane.comp.shells.bash.bugs/15798
Maybe detach the process from the current shell process by calling disown?
The Terminated is logged by the default signal handler of bash 3.x and 4.x. Just trap the TERM signal at the very first of child process:
#!/bin/sh
## assume script name is test.sh
foo() {
trap 'exit 0' TERM ## here is the key
while true; do sleep 1; done
}
echo before child
ps aux | grep 'test\.s[h]\|slee[p]'
foo &
pid=$!
sleep 1 # wait trap is done
echo before kill
ps aux | grep 'test\.s[h]\|slee[p]'
kill $pid ## no need to redirect stdin/stderr
sleep 1 # wait kill is done
echo after kill
ps aux | grep 'test\.s[h]\|slee[p]'
Is this what we are all looking for?
Not wanted:
$ sleep 3 &
[1] 234
<pressing enter a few times....>
$
$
[1]+ Done sleep 3
$
Wanted:
$ (set +m; sleep 3 &)
<again, pressing enter several times....>
$
$
$
$
$
As you can see, no job end message. Works for me in bash scripts as well, also for killed background processes.
'set +m' disables job control (see 'help set') for the current shell. So if you enter your command in a subshell (as done here in brackets) you will not influence the job control settings of the current shell. Only disadvantage is that you need to get the pid of your background process back to the current shell if you want to check whether it has terminated, or evaluate the return code.
This also works for killall (for those who prefer it):
killall -s SIGINT (yourprogram)
suppresses the message... I was running mpg123 in background mode.
It could only silently be killed by sending a ctrl-c (SIGINT) instead of a SIGTERM (default).
disown did exactly the right thing for me -- the exec 3>&2 is risky for a lot of reasons -- set +bm didn't seem to work inside a script, only at the command prompt
Had success with adding 'jobs 2>&1 >/dev/null' to the script, not certain if it will help anyone else's script, but here is a sample.
while true; do echo $RANDOM; done | while read line
do
echo Random is $line the last jobid is $(jobs -lp)
jobs 2>&1 >/dev/null
sleep 3
done
Another way to disable job notifications is to place your command to be backgrounded in a sh -c 'cmd &' construct.
#!/bin/bash
# ...
pid="`sh -c 'sleep 30 & echo ${!}' | head -1`"
kill "$pid"
# ...
# or put several cmds in sh -c '...' construct
sh -c '
sleep 30 &
pid="${!}"
sleep 5
kill "${pid}"
'
I found that putting the kill command in a function and then backgrounding the function suppresses the termination output
function killCmd() {
kill $1
}
killCmd $somePID &
Simple:
{ kill $! } 2>/dev/null
Advantage? can use any signal
ex:
{ kill -9 $PID } 2>/dev/null
I have the following bash script.
#!/bin/bash
while :
do
sleep 2
infiniteProgramm -someParametrs
sleep 10
#in this line I need to stop my infiniteProgramm with bash command (SIGINT) (like Ctrl+C, but automatic)
clear
done
How can I send a SIGINT signal to my infiniteProgramm?
First: run infiniteProgram in the background:
infiniteProgram -someParameters &
Second: retrieve its PID from $!.
pid=$!
Third: kill it.
sleep 10
kill -2 $pid
2 corresponds to SIGINT, see kill -l for the list of all the signals.
a strange thing to me
a script while.sh,it's content is:
while [ 1 ];do
sleep 1
echo `date`
done
run as $while.sh >& while.log & (without nohup or disown or setsid or double fork())
exit and login again can see this process is still exist，it's ppid is 1 and it's tty is ?
my system is rhel6(rhel5 is the same, bash
in centos5.x it must use nohup or disown or do double fork() in code
what happen in rhel6
Is the huponexit shell option set?
$ shopt
...
huponexit off
Bash will send a SIGHUP signal to its jobs if it receives a SIGHUP itself, but it won't signal them when it exits normally unless you enable this option.
For what it's worth this is disabled on both RHEL6 and RHEL5, at least on the systems I just tested. I tried this command:
$ sleep 1000 &
It was not killed when I logged out and logged back in unless I deliberately enabled shopt -s huponexit.
I current have a script that looks like this.
# code
mplayer "$vid"
# more code
The problem is that if this script is killed the mplayer process lives. I wondering how I could make it so that killing the script would kill mplayer as well.
I can't use exec because I need to run commands after mplayer.
exec mplayer "$vid"
The only possible solution I can think of is to spawn it in the background and wait until it finishes manually. That way I can get it's PID and kill it when the script gets killed, not exactly elegant. I was wondering what the "proper" or best way of doing this is.
I was able to test the prctl idea I posted about in a comment and it seems to work. You will need to compile this:
#include "sys/prctl.h"
#include "stdlib.h"
#include "string.h"
#include "unistd.h"
int main(int argc, char ** argv){
prctl(PR_SET_PDEATHSIG, atoi(argv[1]),0,0,0);
char * argv0 = strdup(argv[2]);
char * slashptr = strrchr(argv0, '/');
if(slashptr){
argv0 = slashptr + 1;
}
return execvp(argv0, &(argv[2]));
}
Let's say you have compiled the above to an executable named "prun" and it is in your path. Let's say your script is called "foo.sh" and it is also in your path. Make a wrapper script that calls
prun 15 foo.sh
foo.sh should get SIGTERM when the wrapper script is terminated for any reason, even SIGKILL.
Note: this is a linux only solution and the c source code presented is without detailed checking of arguments
Thanks to Mux for the lead. It appears that there is no way to do this in bash except for manually catching signals. Here is a final working (overly commented) version.
trap : SIGTERM SIGINT # Trap these two (killing) signals. These will cause wait
# to return a value greater than 128 immediately after received.
mplayer "$vid" & # Start in background (PID gets put in `$!`)
pid=$!
wait $pid # Wait for mplayer to finish.
[ $? -gt 128 ] && { kill $pid ; exit 128; } ; # If a signal was recieved
# kill mplayer and exit.
Refrences:
- traps: http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_12_02.html
(Updated) I think I understand what you are looking for now:
You can accomplish this by spawning a new terminal to run your script:
gnome-terminal -x /path_to_dir_of_your_script/your_script_name
(or use xterm -e or konsole -e instead of gnome-terminal -x, depending on what system you are on)
So now whenever your script ends / exits (I assume you have exit 0 or exit 1 in certain parts of the script), the newly spawned terminal will also exit since the script is finished - this will in turn also kill any applications spawned under that new terminal.
For example, I just tested the above command with this script:
#!/bin/bash
gedit &
pid=$!
echo "$pid"
sleep 5
exit 0
As you can see, there are no explicit calls to kill the new gedit process, but the application (gedit) closes as soon as the script exits anyway.
(Previous answer: alternatively, if you were simply asking about how to kill a process) Here's a short example of how you can accomplish that with kill.
#!/bin/bash
gedit &
pid=$!
echo "$pid"
sleep 5
kill -s SIGKILL $pid
Unless I misunderstood your question, you can get the PID of the spawned process right away instead of waiting until it finishes.
Well, you can simply kill the process group instead, this way the whole process tree will be killed, first find out the group id
ps x -o "%p %r %c" | grep <name>
And then use kill like so:
kill -TERM -<gid>
Note the dash before the process group id. Or a one-liner:
kill -TERM -$(pgrep <name>)
Perhaps use command substitution to run mplayer "$vid" in a subshell:
$(mplayer "$vid")
I tested it this way:
tesh.sh:
#!/bin/sh
$vid = "..."
$(mplayer "$vid")
% test.sh
In a separate terminal:
% pkill test.sh
In the orginal terminal, mplayer stops, printing to stderr
Terminated
MPlayer interrupted by signal 13 in module: av_sync