I am running a minecraft server in a screen session. I also am using a named pipe in order to send commands to the minecraft server from other scripts.
I can see output from the server in the screen session, however I cannot enter any. I expected this anyway since I am taking input from the named pipe.
Here's the line I run to start everything:
screen -S minecraft sh startup.sh
Here's startup.sh:
#!/bin/bash
rm mct
if [ ! -p mct ]; then
mkfifo mct && chmod 0777 mct
fi
tail -f mct | java -Xincgc -Xmx2048M -jar minecraft_server.jar
I want to be able to enter commands from the screen session and from the named pipe. Is there a way I can accomplish this? I'm just now messing around with bash scripts, been learning a lot about it today. I just can't seem how to do this.
One approach is to run your tail -f mct concurrently with a command that reads from the console and writes to the same anonymous pipe:
( tail -f mct & cat ) | java -Xincgc -Xmx2048M -jar minecraft_server.jar
Related
It seems that when my screen is locked for some period of time, my S.gpg-agent.ssh disappears, and so in order to continue using my key I have to re-initialise it.
Obviously, this is a relatively frequent occurrence, so I've written a function for my shell to kill gpg-agent, restart it, and reset the appropriate environment variables.
This may be a bit of an 'X-Y problem', X being above this line, but I think Y below is more generally useful to know anyway.
How can I automatically run a command when an extant file no longer exists?
The best I've come up with is:
nohup echo "$file" | entr $command &
at login. But entr runs a command when files change, not just deletion, so it's not clear to me how that will behave with a socket.
According to your comment, cron daemon does not fit.
Watch socket file deletion
Try auditd
# auditctl -w /var/run/<your_socket_file> -p wa
$ tail -f /var/log/audit/audit.log | grep 'nametype=DELETE'
Howto run a script if event occurred
If you want to run a script on socketile deletion, you can use while loop, e.g.:
tail -Fn0 /var/log/audit/audit.log | grep 'name=<your_socket_file>' | grep 'nametype=DELETE' \
while IFS= read -r line; do
# your script here
done
thx to Tom Klino and his answer
You don't mention the OS you're using, but if it's linux, you can use inotifywait from the inotify-tools package:
#!/bin/sh
while inotifywait -qq -e delete_self /path/to/S.gpg-agent.ssh; do
echo "Socket was deleted!"
# Recreate it.
done
I want to have one script which starts a services in another server.
I have tested that the script works as expected in the server where the server is going to run.
This is the code which starts the service and monitors the log until it is in the startup process:
pkill -f "$1"
nohup java -jar -Dspring.profiles.active=$PROFILE $1 &
tail -n 0 -f nohup.out | while read LOGLINE
do
echo $LOGLINE
[[ "${LOGLINE}" == *"$L_LOG_STRING"* ]] && pkill -P $$ tail
done
This works fine as long as I execute that from that machine.
Now I want to call that script from another server:
#!/usr/bin/env bash
DESTINATION_SERVER=$1
ssh root#$DESTINATION_SERVER /bin/bash << EOF
echo "Restarting first service..."
/usr/local/starter.sh -s parameter
echo "Restarting second service..."
/usr/local/starter.sh -s parameter2
EOF
Well, everytime I try that the script of the remote server gets stuck in the "while READ" loop. But as I said, when I execute it locally from the server works fine, and in my "not simplified script" I´m not using any system variable or similar.
Update: I just tried to simplify the code even more with the following lines in the first scenario:
pkill -f "$1"
nohup java -jar -Dspring.profiles.active=$PROFILE $1 &
tail -n 0 -f nohup.out | sed "/$L_LOG_STRING/ q"
I'd say the problem is some how in the "|" through ssh, but I still can find why.
it seems that the problem comes from not having an interactive console when you execute the ssh command, therefore the nohup command behaves strangly.
I could solve it in two ways, outputing the code to the file explicitly:
"nohup java -jar -Dspring.profiles.active=test &1 >> nohup.out &"
instead of:
"nohup java -jar -Dspring.profiles.active=test &1&"
Or changing the way I access via ssh adding the tt option (just one did not work):
ssh -tt root#$DESTINATION_SERVER /bin/bash << EOF
But this last solution could lead to other problems with some character, so unless someone suggests another solution that is my patch which makes it work.
I'm trying to redirect stdin to a FIFO with bash. This way, I will be able to use this stdin on an other part of the script.
However, it doesn't seem to work as I want
script.bash
#!/bin/bash
rm /tmp/in -f
mkfifo /tmp/in
cat >/tmp/in &
# I want to be able to reuse /tmp/in from an other process, for example :
xfce4-terminal --hide-menubar --title myotherterm --fullscreen -x bash -i -c "less /tmp/in"
Here I would expect , when I run ls | ./script.bash, to see the output of ls, but it doesn't work (eg the script exits, without outputing anything)
What am I misunderstanding ?
I am pretty sure that less need additional -f flag when reading from pipe.
test_pipe is not a regular file (use -f to see it)
If that does not help I would also recommend to change order between last two lines of your script:
#!/bin/bash
rm /tmp/in -f
mkfifo /tmp/in
xfce4-terminal --hide-menubar --title myotherterm --fullscreen -x bash -i -c "less -f /tmp/in" &
cat /dev/stdin >/tmp/in
In general, I avoid the use of /dev/stdin, because I get a lot of surprises from what is exactly /dev/stdin, especially when using redirects.
However, what I think that you're seeing is that less finishes before your terminal is completely started. When the less ends, so will the terminal and you won't get any output.
As an example:
xterm -e ls
will also not really display a terminal.
A solution might be tail -f, as in, for example,
#!/bin/bash
rm -f /tmp/in
mkfifo /tmp/in
xterm -e "tail -f /tmp/in" &
while :; do
date > /tmp/in
sleep 1
done
because the tail -f remains alive.
i have a script that fires remote commands on several different machines through ssh connection. Script goes something like:
for server in list; do
echo "output from $server"
ssh to server execute some command
done
The problem with this is evidently the time, as it needs to establish ssh connection, fire command, wait for answer, print it. What i would like is to have script that would try to establish connections all at once and return echo "output from $server" and output of command as soon as it gets it, so not necessary in the list order.
I've been googling this for a while but didn't find an answer. I cannot cancel ssh session after command run as one thread suggested, because i need an output and i cannot use parallel gnu suggested in other threads. Also i cannot use any other tool, i cannot bring/install anything on this machine, only useable tool is GNU bash, version 4.1.2(1)-release.
Another question is how are ssh sessions like this limited? If i simply paste 5+ or so lines of "ssh connect, do some command" it actually doesn't do anything, or execute only on first from list. (it works if i paste 3-4 lines). Thank you
Have you tried this?
for server in list; do
ssh user#server "command" &
done
wait
echo finished
Update: Start subshells:
for server in list; do
(echo "output from $server"; ssh user#server "command"; echo End $server) &
done
wait
echo All subshells finished
There are several parallel SSH tools that can handle that for you:
http://code.google.com/p/pdsh/
http://sourceforge.net/projects/clusterssh/
http://code.google.com/p/sshpt/
http://code.google.com/p/parallel-ssh/
Also, you could be interested in configuration deployment solutions such as Chef, Puppet, Ansible, Fabric, etc (see this summary ).
A third option is to use a terminal broadcast such as pconsole
If you only can use GNU commands, you can write your script like this:
for server in $servers ; do
( { echo "output from $server" ; ssh user#$server "command" ; } | \
sed -e "s/^/$server:/" ) &
done
wait
and then sort the output to reconcile the lines.
I started with the shell hacks mentionned in this thread, then proceeded to something somewhat more robust : https://github.com/bearstech/pussh
It's my daily workhorse, and I basically run anything against 250 servers in 20 seconds (it's actually rate limited otherwise the connection rate kills my ssh-agent). I've been using this for years.
See for yourself from the man page (clone it and run 'man ./pussh.1') : https://github.com/bearstech/pussh/blob/master/pussh.1
Examples
Show all servers rootfs usage in descending order :
pussh -f servers df -h / |grep /dev |sort -rn -k5
Count the number of processors in a cluster :
pussh -f servers grep ^processor /proc/cpuinfo |wc -l
Show the processor models, sorted by occurence :
pussh -f servers sed -ne "s/^model name.*: //p" /proc/cpuinfo |sort |uniq -c
Fetch a list of installed package in one file per host :
pussh -f servers -o packages-for-%h dpkg --get-selections
Mass copy a file tree (broadcast) :
tar czf files.tar.gz ... && pussh -f servers -i files.tar.gz tar -xzC /to/dest
Mass copy several remote file trees (gather) :
pussh -f servers -o '|(mkdir -p %h && tar -xzC %h)' tar -czC /src/path .
Note that the pussh -u feature (upload and execute) was the main reason why I programmed this, no tools seemed to be able to do this. I still wonder if that's the case today.
You may like the parallel-ssh project with the pssh command:
pssh -h servers.txt -l user command
It will output one line per server when the command is successfully executed. With the -P option you can also see the output of the command.
I have a start server script
startserver.sh
It will run as background task startserver.sh &
the script need to run for sometime until it can really run in running state.
The running state could write into log file server.log when it is ready.
So I need to know when the server is really run by executing a bash cmd. If not, I need to wait until the Running state is shown in the server.log.
Can i achieve this in bash?
try something like this
mkfifo my_fifo
tail -f server.log >my_fifo &
tail_pid=$!
perl -ne '/pattern/&&exit' <my_fifo
kill $tail_pid
rm my_fifo
EDIT : perl command can be replaced with
grep -l 'pattern' <my_fifo >/dev/null
or if grep support this option
grep -q 'pattern' <my_fifo