In order to start gui-programs with parameters, I often find myself opening a terminal (in my case urxvt): starting the corresponding program with 'nohup' or 'disown', and then exiting the terminal. This keeps the program running as desired, but is not too comfortable. I do not use any multiplexer like tmux or screen, this would circumvent this problem. I would like to be able to start a terminal, which would automatically disown and exit after one command was issued. Any ideas how this can be achieved?
Thanks in advance
There are more elegant ways of solving this problem, but here's a solution based on what you've described:
$ (xclock &); exit
Replace xclock with the GUI program you want to run.
Related
I have this node.js server which, once spawned, expects some input from stdin. The inputs shouldn't be given straight away: I need to wait for some event before giving them (e.g. a connection from somebody). If I give the commands and close the shell, the server shuts itself down. I would like to give the input to the server and close my shell (effectively leaving the server running).
I know that to run a process in background I need to do for example node my_server.js &, but this prevents the input from the command line. I would like to give this input AND then put it in background. Modules like forever puts it in the background automatically without letting me giving the inputs through stdin.
Moreover putting the script in background kills anyways the server when closing the shell.
Any suggestion?
Thanks
I did a quick test just using gedit in Ubuntu 12.04, and it worked.
Start your node app like so "node app.js arg1 arg2" however you want to and hit enter to start the program. Then hit CTRL-z once your program has started running. This gives you the terminal back but stops the process in the background. To let it run in the background now, simply "bg" and hit enter. This will let the process keep running now but in the background.
You can confirm you are still up with the command "ps -ef | grep node" which should show your program still running.
However, this does still leave the node process attached to the terminal window so when you close the terminal window it will close the process. But I think this will get you most of what you seem to be looking for quick and easy.
You asked for any suggestion, so here it is: make your server able to start without user interaction. The simplest way to do it is probably to create a file containing exactly the input needed by the server, then starting it like this:
node my_server.js < my_input.txt &
If the input needed depends on what the server outputs (ouch), use expect(1). If possible, subvert the whole thing and use a module like commander to get your inputs from the command line instead of stdin.
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
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.
Besides using top, is there a more precise way of identifying if the last executed command has finished if I had to check in a separate session over Putty?
pgrep
How about getting it to run another command immediately after that sets a flag.
$ do_command ; touch I_FINISHED
then when the command finishes it'll create a file called I_FINISHED that you
can look for.
or something more sophisticated that writes to a log file if you're doing it
multiple times.
I agree that it may be a faster option in the long run to have your program write to a log file or create a notification. Just put it at the end of the executed code, past the part that you suspect may cause it to hang.
ps -eo cmd
Lists all processes, and displays the command line, as 'typed' when the command started, so you will be able to tell your script apart from anything else running written in Perl.
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