I have a Sky wireless sensor node and a script which prints the output from the node.
sudo ./serialdump-linux -b115200 /dev/tmotesky1
If I start this script before my pc detects the node, I get the following error:
/dev/tmotesky1: No such file or directory
But if I wait for example 20 seconds, I miss the initial prints (which are important).
Is there a way to detect if the /dev/tmotesky1 exists?
Something like
while [ ! -f /dev/tmotesky1 ] ; do sleep 1; print 'Waiting...'; done
Thanks in advance!
Your code indicates that you are using Linux where you can use the hotplugging mechanism.
On generic systems, you can write an udev rule (--> see with udevadmin monitor -e what happens when you attach the device) which starts e.g. a program or writes something into a pipe. When systemd is used, you can start a service (see man systemd.device).
On small/embedded systems it is possible to write a custom /sbin/hotplug program (set in /proc/sys/kernel/hotplug) instead of using udev.
Related
I have a very limited list of software that I can install on an (IOT edge) device. I have minicom and chat commands (in addition to standard commands like echo and cat), and need to write to a serial device a command and read the response.
The device in question is a modem, and I need to run AT commands on it. If using minicom and setting up the menu etc. I can run these commands normally, and get the output. The problem is that I have around a thousand of these devices, so setup and data logging needs to be automated.
So within these parameters is there a way to run minicom and capture the output without any interactive elements? I have tried
minicom -S scriptfile -C outfile
where scriptfile (for now) contains following:
sleep 1
send "AT"
This seems to ignore the sleep command, and outfile is created, but is left empty. Also what would I need to add to the command that it wouldn't open a session or interactive element?
I use GMediaRenderer to send audio via UPNP from a Raspberry Pi. Occasionally, for reasons unknown, I have to SSH into my Pi and send the command sudo service gmediarenderer restart to get it to work properly. I'd like to add a command to crontab or similar that periodically checks whether the service is running properly. I already have a crontab entry that checks whether the service is running, and starts if it isn't. The trouble I'm having is that sometimes, even though the service is running, it doesn't appear to be communicating with UPNP control points. Executing the restart command brings it back, so I assume it is simply the case that the service has crashed but not closed down.
Does anyone know how to programmatically check (preferably using a bash script) whether the GMediaRenderer service is up and running?
I have found a solution to this. The command gssdp-discover returns a list of active renderers. I setup a sudo crontab job to run a bash script every minute that checks whether or not a particular renderer is running, and to restart gmediarenderer if it isn't found.
The following command will list your active renderers:
gssdp-discover -i wlan0 --timeout=3
Change wlan0 above depending on your specific network connection. In my case, the renderer that I'm interested in is listed as urn:av-openhome-org:service:Info:1 (run the command with and without the renderer active, and look for the one that only appears when running). So, my bash script contains the following:
gssdp-discover -i wlan0 --timeout=3 --target=urn:av-openhome-org:service:Info:1 | grep available &> /dev/null
if [ $? == 0 ]; then
echo "OpenHome renderer is already running"
else
echo "restarting gmediarenderer"
/etc/init.d/gmediarenderer stop
/etc/init.d/gmediarenderer start
fi
I'm trying to use gammu and gammu-smsd to send and receive sms with my raspberry pi using a Huawei intrnet key.
My problem is that when I send an sms from my phone to raspberry pi, it read the sms, it try to start the program linked at RunOnReceive = in /etc/gammu-smsdrcn file but then, it says: Process failed with exit status 1.
I tried any kind of solution but I'm not capable to solve this problem by my self; I've set each permission on the script.
Can someone help me?
Thank you a lot.
You no doubt have this sorted by now, but I have just been through the same trip, tore out a lot of hair and finally made it out the back .... :-)
I'm using a ZTE stick with wvdial for internet connection. The stick appears as modems on /dev/USBtty0, 1 and 2. wvdial uses USBtty2, so gammu (I think) has to use a different one.
So I installed gammu/gammu-smsd on USBtty1 in gammu-config and /etc/gammu-smsdrc. The receive daemon gammu-smsd fires up automatically on boot.
First trap for young players - if you want to send an SMS with
echo "whatever" | gammu sendsms TEXT xxxyyyzzzz (where the last is the phone no) - you need to kill the receive daemon for that to work ie
service gammu-smsd stop # kill receive daemon
echo etc etc gammu etc etc # send the SMS
service gammu-smsd start # revive the receive daemon
Now for the RunOnReceive thing ...
start with sudovi - gives some config file to edit. There's a line in there about pi BLAH-BLAH-BLAH as a sudoer. Duplicate it with gammu BLAH-BLAH-BLAH. Same BLAHs. Save it.
It's something to do with permissions - I'm not an expert here :-)
So my RunOnReceive line is { sudo /home/pi/procSMS.sh $SMS_1_TEXT }
The script didn't seem to know what $SMS_1_TEXT was, so I passed it through as a parameter - inside the script it's treated as $1. It works.
While testing I ran a process in another window - just tail -f /var/log/syslog which lets you watch it all in real time ...
I was getting the same error on Raspberry Pi in combination with Huawei E3131 (Process failed with exit status 1) but I solved it.
make sure you have file permissions set well. Gammu runs deamon under "gammu" user by default. So you can change it (/etc/init.d/gammu-smsd) to user who is already located in your system and has rights for executing the script. Or change script permissions by following: chmod 755 script.sh. It means you give execute rights to other users too.
In fact there is additional option. Run gammu deamon with parameter -U username. Unfortunatelly it did not work for me when I used root user.
PS: I would recommend to not to place the script inside /etc directory. Use /home directory instead.
turn on debuging in /etc/gammu-smsdrc. Use parameters: logformat and debuglevel in section smsd. Default log is located in /var/log/syslog. May be it helps you deeply localize the problem.
And the best at the end... I found that gammu returns the error even if it runs the script well! You have to write exit code inside you bash script. If you do not specify an exit code, gammu represents it as error 1. Add exit 0 in case of success in the end of the script and error message disappears.
I'm running a Bukkit (Minecraft) server on a Linux machine and I want to have the server gracefully shut down using the server's stop command and the computer suspend at a certain time using pm-suspend from the command line. Here's what I've got:
me#comp~/dir$ perl -e 'sleep [time]; print "stop\\n";' | ./server && sudo pm-suspend
(I've edited by /etc/sudoers so I don't have to enter my password when I suspend.)
The thing is, while the perl -e is sleeping, the server is expecting a constant stream of bytes, (That's my guess. I could be misunderstanding something.) so it prints out all of the nothings it receives, taking up precious resources:
me#comp~/dir$ ...
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>...
Is there any such thing as a buffered pipe? If not, are there any ways to send delayed input to a script?
You may want to have a look at Bukkit's wiki, which recommends an init script for permanently running servers.
This init script uses rather unconventional approach to communicate with running server. The server is started in screen session, then all commands are send to the server console via screen, e.g.
screen -p 0 -S $SCREEN -X eval 'stuff \"stop\"\015'
See https://github.com/Ahtenus/minecraft-init/blob/master/minecraft
This approach suggest that bukkit may be expecting standard input to be attached to a terminal, thus requiring screen wrapper (which is itself terminal emulator) for unattended runs.
I have a program that runs as a daemon, using the C command fork(). It creates a new instance that runs in the background. The main instance exists after that.
What would be the best option to check if the service is running? I'm considering:
Create a file with the process id of the program and check if it's running with a script.
Use ps | grep to find the program in the running proccess list.
Thanks.
I think it will be better to manage your process with supervisord, or other process control system.
Create a cron job that runs every few minutes (or whatever you're comfortable with) and does something like this:
/path/to/is_script_stopped.sh && /path/to/script.sh
Write is_script_stopped.sh using any of the methods that you suggest. If your script is stopped cron will evaluate your script, if not, it won't.
To the question, you gave in the headline:
This simple endless loop will restart yourProgram as soon as it fails:
#!/bin/bash
for ((;;))
do
yourProgram
done
If your program depends on a resource, which might fail, it would be wise to insert a short pause, to avoid, that it will catch all system resources when failing million times per second:
#!/bin/bash
for ((;;))
do
yourProgram
sleep 1
done
To the question from the body of your post:
What would be the best option to check if the service is running?
If your ps has a -C option (like the Linux ps) you would prefer that over a ps ax | grep combination.
ps -C yourProgram