I'm working on a GWT application that has a feature to change system's date and time. In order to execute the linux date command (for example: date 052810242012) the following line is executed but after that tomcat freezes:
Runtime.getRuntime().exec(this.command); // where this.command is the date command
I've realized that even if the application is up and running and I change the system date and time in a terminal, it freezes the application anyway.
Could someone explain why ?
Firstly, I think the command that you wanted to execute is a root-only command，so you must make sure that the owner of your application is a sudoer，and it has right to execute that command.
Second, Runtime.getRuntime().exec() offers an interface to execute system command for JAVA but there is a difference between executing directly on the temina because it deals with the input and output itself, and will not print on the screen like teminal so you must deal with the result of the command in the JVM or write the command into a executable shell script with no output and call
Runtime.getRuntime().exec(sudo","./a.sh"};
Finally, the problem you mention when you change the date and time in a teminal leads to freeze the application, I've never seen this before. Could you just explain its detail ？
Related
I have a LiveCode app standalone that needs to know if there is a job waiting in the MacOS print queue before printing. If app user 1 prints the 2 page report and just one page prints (out of paper) then user 2 comes along and prints the report, the first page out is user 1's report and this is causing mixups. I would like to check the MacOS print queue and prevent printing if there is a job already waiting.
It's not something I've ever needed to do, but I suspect that this capability is not included in LiveCode natively. Instead your best bet will probably be to use LiveCode's shell() function to run a unix terminal command. For instance, lpstat is a command line utility that allows you to query various things about printers connected to your Mac. The following command, run in the MacOS terminal, shows which printers are available and their current status.
lpstat -p
In LiveCode you use the shell() function to call this command line utility, like so:
put shell("lpstat -p") into tPrinterStatus
To find out more about lpstat, open the Terminal and look up the man page:
man lpstat
Lots of options for that utility will appear. There should be one that gives you the information you need.
I have a python script that takes some inputs from the user & then executes the code based on the input. The code takes some time to complete; during this code runtime the user can close the terminal(the code is run from a Linux machine)
As soon as the user closes the terminal the script stops as well. I know there are options like nohup but it wouldn't accept any input(where input is required in my script).
How can I fix this?
Requirement is -
Run the script, enter the inputs
Let the code run in the background even if the terminal is closed
Also is there a way to write whatever is being printed in the terminal(during the script runtime) to some file
Linux's screen tmux served my purpose.
There is a work around possible,
you can split your programm into two parts.
And start your background task with:
import os
usr_inp=input("test input: ")
os.popen(f"python3 background_task.py {usr_inp} &")
This should start the other programm in the background, there you can use the input over the sys.argv[1] variable.
(Usually it's not recommended using os.popen)
There's quite a bit of information out there on this topic, but for some reason I just can't get it to work. This is on a raspberry pi running the 'DietPi' flavor over the raspian distro, and is perhaps what separates my question from the others.
So I have a GUI application that I wish to launch at boot, after the LXDE session has begun. So I have utilized the following file here:
/etc/xdg/lxsession/LXDE/autostart
and added the line:
#/myapplication
This works, however, it launches multiple instances of this program, and the first one always crashes. This creates problems because there's some competition for resources (IO, files, etc). So what I did was create script file, /myapplication-autostart.sh instead like so:
if pgrep "myapplication" > /dev/null
then
echo "my application is already running"
else
/myapplication
fi
and then changed /etc/xdg/lxsession/LXDE/autostart to #/myapplication-autostart.sh. Now what I find is the program launches once, but the instance crashes. It crashes when it attempts to create a window (opencv imshow). This is strange because the program will also run headless if an X-session is not available, but for some reason it crashes and I do not know where to check why.
Also, to test it wasn't an issue with the script file, I commented everything out except the /myapplication and I have found the script file runs in a continuous loop and every time I close the application it opens back up. I'm not sure why this is either.
I've tried adding a sleep delay in the script and it does not help. For whatever reason, it seems the LXDE autostart script is ran at least 3 times when booting the pi and the circumstances around the first cause the program to crash. Does anybody understand this sequence and behavior of calling this autostart script?
It is also possible to use the XDG standard Autostart - which is independent of the used desktop environment - by placing desktop files at
$XDG_CONFIG_HOME/autostart (by default ~/.config/autostart)
or for system-wide autostarts at $XDG_CONFIG_DIRS/autostart (by default /etc/xdg/autostart).
Such a .desktop-file could look like:
[Desktop Entry]
Type=Application
Version=1.0
Name=JDownloader
Exec=/usr/local/bin/my-application.sh
Categories=Utilities
The specification of desktop-files can be found at freedesktop.org.
Here was the final solution...
/etc/xdg/lxsession/LXDE/autostart added the line:
/myapplication-autostart.sh
and /myapplication-autostart.sh was changed to:
#!/bin/bash
if pgrep "myapplication" > /dev/null
then
echo "my application is already running"
else
if [[ "$DISPLAY" = ":0" ]]
then
/myapplication
fi
fi
I had to write the display variable to file in combination with the errors to file to discover the issue. At login 2 X sessions were created, display ":1" and display ":0", in that sequence. Display ":1" crashed because, although not headless, it was not initialized to a particular resolution and there was some resizing code in my program. Display ":0" was the actual display on the HDMI out and the one I wanted. Really, the conditional check to see if the application isn't necessary but I left it in there to be safe. I could have also left the # on the LXDE autostart file but it got annoying in the cases I wanted to close the application because it'd keep re-opening. Possibly I'll put it back later.
Thanks for the help!
First, some comments about opening several instances of the program: when you use "#" at the beginning of the line on the startup file (ex.: #/myapplication), this requests your system to try to launch the program, but if the program fails to open correctly, then the system will try to open it multiple times until it opens correctly -- if you remove "#" from the line beginning, then the system will only try to open the program once.
Now, to find out why the program is failing, I advise you to add
2> /file/log
to the end of every command on your script. Doing so would append any error message to a log (/file/log), and analyzing those error messages would be key to find out why the program is misbehaving.
One important note: if your program needs root privileges to run, then it will fail when called via /etc/xdg/lxsession/LXDE/autostart, as this method calls programs without elevated permissions.
This is an old thread but I was having problems getting autostart to start all the tasks listed. After many days I concluded there were one or more "invisible" characters that autostart didn't like. So I deleted the lines for the tasks that didn't start and retyped them. That solved the problem!
I think I corrupted the lines because I was editing some of the lines on my Windows computer. It was likely inserting CR with LF or some other stuff. I WILL NEVER EDIT TEXT FOR LINUX USING WINDOWS!
Maybe someone else will hit this problem and this may help them. I don't know where else to put this information.
I have a program that needs to start another program. On my mac I did this using system("open path"), but on linux that doesn't work. and using system(./path) is not what I want since than it overtakes the running program.
So is there any way to get the same behaviour as the mac 'open path' command on linux?
(linux noob btw:p)
If you're running the application in a GUI environment, this should be possible but the approach is different. You need to start a new terminal instance explicitly.
Determine the path to your terminal application. This depends on the linux distribution.
Next, check the documentation of that particular terminal application and find out how it can be started to run an application (your application) instead of a shell. This probably involves using some application-specific command line options. Test that in a terminal window, until you have a command line that gives you the desired result. Things could get a little tricky if your application needs command line arguments as well. Use the -- option where necessary.
Then, all you need to do is run that command line from your "parent" application. I would advise however to not use system(). The exec... family functions (using fork and wait) provide better control.
I'm looking for a method to check from within my shell script that script specific completion have been initialized by user using complete -F ...
I want this check to print out an advice on how to initialize the completion like:
Warning: Auto completion is not initialized. Please run : source ....; complete -F ...
The problem is that the script,being run in a sub-shell has no information about "complete" environment of the parent shell where user is working.
So complete -p| grep my-script-name never return any result.
User is expected to run "source" and "complete" commands or add them into his .bashrc manually, because we're working on a server where we have no access to the bash completion system directory.
Alternatively if you know a method of initializing(and not only checking) the auto-complete from within the script, I would happily accept it.
The only way your script can have access to such information for the parent shell is if it is included instead of executed as a sub-shell. Rather than instructing your users they can include some configuration, you can design your script so it works whether it is run or included.
Then you can simply inform your users that if they want completion enabled they need to include your script rather than run it as an executable script (with instuctions to use source or . as you wish).
However, in this case, I would be inclined to either add this information in documentation or add it into a banner which is always displayed (but can be disabled with an option switch like -q), rather than support two modes of running the script (since the gain is so small).
Either you want every user to use bash completion (which I don't think is good, for example I prefer to have it turned off), or let users decide themselves, but having them this message printed out on each TABTAB is a threat, don't you think?
I'd put into /etc/bash.bashrc what you think every user should run.