Say for example, to open multiple instances of gedit editor I wrote a shell script like this-
gedit&
gedit&
gedit&
gedit&
But after I ran my shell script ./example.sh, I can find only one instance of gedit! I've even used the & operator, so that the shell doesn't wait for one instance to finish. Still I cannot see four instances of gedit.
Also I tried directly from the command prompt. If I just enter gedit& on the command line, it showed 1906 ( this is the PID of the newly created gedit process ), started one new gedit instance and returned to prompt again. When I typed gedit& on the command line, it showed 1909 this time, but no new instance of gedit! And I couldn't find any process with PID 1909 in the System Monitor too. Where did this new process go away?
Is the happening specific to gedit? If so, what is the generic behavior when creating multiple instances of a program?
It is specific to gedit. You are likely looking for gedit --new-window &.
From man gedit:
--new-window
Create a new toplevel window in an existing instance of gedit.
I came here, trying to start multiple instances of audacious.
Allowing only one instance is actually harder to implement, because the program needs to find and communicate with the instance already running. This is done via D-Bus. In order to prevent communication with the already started instance you can run the program in another D-Bus session:
nohup dbus-run-session audacious &
nohup dbus-run-session audacious &
Note: nohup will keep the program running even if the terminal is to be closed.
This method should also work for other programs which do not let the user choose between multiple instance vs. one instance.
Beware that this might introduce bugs, if multiple instances are accessing the same configuration files.
Tested with xfce 4.14.1 and dbus 1.12.20
For Scite:
scite -check.if.already.open=false &
A word of caution:
If you, like me, have your system running for multiple months and have edited some of your shortcuts or aliases to open with this hack, then after a while some programs will not start anymore because there are already too many open D-Bus session. In this case you have to kill the started D-Bus sessions, which do not close when the started program closes. The other way around, killing the D-Bus session, will also kill the opened program, so use with care! For me personally, I have some long running autostarted programs which I want to keep open (firefox), so I kill all but the first 10 D-Bus sessions with this:
for pid in $( ps --sort start_time -aux | grep dbus-daemon | tail +10 | awk '{ print $2; }' ); do kill $pid; done
The cleanest solution would be to write a launcher script which waits for the program to finish and then closes the opened D-Bus sessions. But this is a bit more difficult than it seems because it is hard to find the PID of the corresponding D-Bus session.
P.S.: I also used this hack because there seems to be some program on my system which, after a while, slows down the system's default file open dialog to take multiple minutes if not longer to open! Programs then seem to hang when trying to save or open files. A new D-Bus sessions seems to fix this for some reason. While writing this, I found that pkill gvfsd-trash also works and that it may have been this bug. So until this gets shipped, I guess I'll add pkill gvfsd-trash to my crontab.
This seems specific to gedit, perhaps there's some option to turn off the check for a running instance.
Looks like gedit is first looking for a running instance and simply ignores further start-requests (just a wild guess). But the manual page says, that you can open another window:
--new-window
Create a new toplevel window in an existing instance of gedit.
That wouldn't exactly solve your problem, but maybe that's what you were looking for in the first place.
Good luck,
Alex.
Using this in a script. I've found that it does what I need it to:
#!/bin/bash
xterm -e "gedit; bash" &disown
Related
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 need to open a new terminal from my script but I want to wait for that terminal to exit before continuing with the rest of the script. I know that
gnome-terminal -e 'nano test.txt'
opens a new terminal window with "test.txt" opened in nano, but the calling script does not get blocked. Is there a way to wait for the new terminal to exit, before continuing the original script?
For the benefit of the reader: The answer from #Feiteira used to be the correct answer, but is no more supported by gnome-terminal. Option --disable-factory got removed from gnome-terminal.
To explain the different observation of several people here:
gnome-terminal only blocks, if it is the first instance of it. This single instance then acts as a server for all future invocations of gnome-terminal. Those other gnome-terminal calls then hand everything over to this server and immediately terminate. So you can observe both behavior: "blocking" (when it is the one-and-only single instance) and "nonblocking" (when another instance is already running).
There is a wrapper, for example used by Ubuntu 16.04, which emulates this missing option. However this wrapper is complex. This is done by starting another server (with another service name). And for this server, the same assumption holds (you can attach other gnome-terminals to this server, and those others then come back immediately as well).
My suggestion is to stop using gnome-terminal and to switch to something, which works right out of the box. For example xfce4-terminal officially supports all those little absolutely necessary options for a mature terminal window:
xfce4-terminal --disable-server -x nano test.txt
Also xfce4-terminal introduces --hold which allows you to see the output of a command. Sadly --hold has a bug (at least under Ubuntu 16.04), which causes it to (often) truncate the output (the terminal is closed too early if a command terminates, so all still buffered output of the PTY does not make it to the window. This is a very well known common bug if you are not careful enough with PTYs).
The option you want is: --disable-factory
gnome-terminal --disable-factory ...
You could use && for instance (also see What is the purpose of "&&" in a shell command?):
gnome-terminal -e 'nano test.txt' && sleep 5 && echo "Done"
I have to connect to a linux server from my own Ubuntu machine and operate directly on the server.
A dozen of folder names are listed in a LIST file. How to write sth. (like a bash script?) to carry out the following procedures?
for fold_name in LIST {
/******on my own Ubuntu*******/
-- open 2 new tabs of prompt terminal
-- run an ssh command in both
-- then input passwd and log in automatically in both
/******on the linux server*******/
-- cd to directory xxx/fold_name in both
-- run aaa.exe in 1st tab
-- vim sth in the 2nd tab
}
Once the loop of open-tab-login is solved, I guess the second part is routine as simple bash script except that I don't know how to specify between 2 tabs, either.
The point is I want all tabs in the same terminal. To this end, manually, I often Ctrl+Alt+T to create a prompt and Ctrl+Shift+T to open many tabs within it. And ssh...cd...... in each one. You see how annoying and cumbersome it is!
There are a few things you might like to research, which will get you a little closer.
You can run an ssh without a password, if you use an ssh key. Check out ssh-keygen, and the -i option in ssh.
Opening up tabs in gnome-terminal can be done via the method described here: Open a new tab in gnome-terminal using command line
You can run specific commands (e.g. aaa.exe) on a remote box over ssh, by including the command after the ssh: ssh user#remotehost aaa.exe.
If you want multiple commands, try enclosing them in quotes: ssh user#remotehost "cd /xxx; aaa.exe". Vim does not need to be in the directory in question in most cases: ssh user#remotehost vim /xxx/filename"
If you want to do something interactive (like vim), include the -t flag in ssh.
The tabs will be independent of each other - I'd probably run half of the command in one window, the other (e.g. runnning aaa.exe in one window, using one command, and the vim in another window, using another command, that I just happen to run at the same time. This way I can resize the windows, and arrange them relative to each other, and see both at once.
-- open 2 new tabs of prompt terminal
This depends on which desktop you're using. For gnome, gnome-terminal takes the -e option to specify the script to execute in the new terminal window. So, for something like this, you would execute gnome-terminal -e $script &, placing each instance of gnome-terminal in the background.
If you're using a different desktop, other terminal applications typically have a similar option. So, you'd point the terminal application to a script that's going to run in the terminal, and complete the rest of your task for you.
-- run an ssh command in both
-- then input passwd and log in automatically in both
This is going to be more complicated. The classical solution is the expect utility. There might be other similar tools that do similar things, but expect is pretty much the usual way these kinds of things have been done in the past. When it comes to trying to automate an interactive application, expect is really the only way to go. Unfortunately, expect uses a somewhat arkane syntax, that first-time users typically find confusing, and hard to understand. I grumble, every time I see no other alternative but to use expect to automate something, but this is pretty much the only option that's usually available.
Some programs return immediately when launched from the command line, Firefox for example. Most utilities (and all the programs I've written) are tied to the shell that created them. If you control-c the command line, the program's dead.
What do you have to add to a program or a shell script to get the return-immediately behavior? I guess I'm asking two questions there, one for shell scripts and one for general, if they're different. I would be particularly interested to know if there's a way to get an executable jar to do it.
I'm almost embarrassed to ask that one but I can't find the answer myself.
Thanks!
start cmd
on Windows,
cmd &
on *nux
Here substitute
cmd = java -jar JarFile.jar
On *nux the fg and bg commands are your friends as well ...
You need to basically need to fork a process or create a new thread (or pretend to)
in *nux you can do this with an & after the command like this /long/script & or in windows you can create a BATCH file that executes your processes then exits (it does this naturally).
NOTE: there's no particularly good way to reference this process after you're forked it, basically only ps for the process list. if you want to be able to see what the process is doing, check out using screen (another linux command) that will start a session for you and let you "re-attach" to the screen.
to do this, install screen (sudo apt-get install screen or yum install screen). then type screen to create a new session (note, it will look like you didn't do anything). then, run your /long/command (without the &), then press CTRL + A + D (at the same time) to detach from it (it's still running!). then, when you want to re-attach, type screen -r.
Additionally, look for flags in any help message that allow you do this without using the above options (for instance in synergy you can say synergy --background)
A wrapper script consisting of nothing but:
your_prog_or_script &
Will launch the target and exit immediately. You can add nohup to the beginning of that line so it will continue running if the shell is exited.
For an executable program (as opposed to a shell script), on Linux/Unix use fork() and exec() and then exit the parent process, which will return to the shell. For details see the man pages, or some page like http://www.yolinux.com/TUTORIALS/ForkExecProcesses.html.
I am using Putty to connect to a remote server. What I want to know is if there is any way to write my commands and allow them to keep running after I close the session with Putty. The reason for this is that I do not want to keep the computer ON all the time. Is there any way to do this?.
Update with the solution
For my question as it is presented the best solution is use one of the commands provided such as nohup, because you do not have to install any additional software. But if you are in the same problem use screen, install it and use it. It is amazing.
I have selected the answer of Norman Ramsey as favourite because propose several solutions using commands and screen. But please check the other answers specially the one of PEZ, then you get an insight of what screen is able todo.
screen! It's the best thing since sliced bread. (Yeah, I know others have already suggested it, but it's so good the whole world should join in and suggest it too.)
screen is like, like, ummmm ... like using VNC or the like to connect to a GUI destop, but for command shell windows. You can have several shell "windows" open at once in the same screen session. You can do stuff like:
Start a screens session using "screen -dR" (get used to using -dR)
run some commands in one window
press CTRL-A,C to create a new window open a file there in vim
press CTRL-A,0 to go back to the first window and issue some command on the file you just edited
CTRL-A, 1 to go back to your vim session
CTRL-A, C for yet another window and maybe do "sudo - su" (because you just happen to need a full root shell)
CTRL-A, 0 and start a background process
CTRL-A, C to create yet a new window, "tail -f" the log for that background process
CTRL-A, d to disconnect your screen then CTRL-D to disconnect from the server
Go on vacation for three weeks
Log on to the server again and issue "screen -dR" to connect to your existing screen session
check the log in the the fourth window with CTRL-A, 3 (it's like you've been there watching it all the time)
CTRL-A, 1 to pick up that vim session again
I guess you're starting to get the picture now? =)
It's like magic. I've been using screen for longer than I can remember and I'm still totally amazed with how bloody great it is.
EDIT: Just want to mention there's now also tmux. Very much like screen, but has some unique features, splitting the windows being the most prominent one.
nohup, disown, and screen are all good but screen is the best because unlike the other two, screen allows you to disconnect from the remote server, keep everything running, and then reconnect later to see what is happening. With nohup and disown you can't resume interacting.
Try using GNU Screen. It allows you to have several shells open at once. And you can disconnect from those running shells (i.e. close session with Putty) and they will keep doing their thing.
What you are looking for is nohup.
See the wiki link for how to use it.
screen is the best.
Try:
screen -dmS "MyTail" tail -f /var/log/syslog
This start command in background.
Use screen -r to list, and or screen -r Mytail to enter session.
If more users need access same session, use: screen -rx MyTail, and both or more users share the session.
If you can't use screen (because, for instance, your SSH session is being programmatically driven), you can also use daemonize to run the program as a daemon.
One way that works well for me is at.
at works like cron, but for a one-time job. I used it today to download a large file without having to keep my session alive.
for example:
$ at 23:55
at> wget http://file.to.download.com/bigfile.iso
at> ^D
You pass at a time (in the future) and it gives you a prompt. You enter the commands you want to run at that time and hit ctrl+d. You can exit out of your session and it will run the commands at the specified time.
Wikipedia has more info on at.
./command & disown
ssh localhost && ./command && exit