process interview questions
Top process frequently asked interview questions
I'm working on a linux machine through SSH (Putty).
I need to leave a process running during the night, so I thought I could do that by starting the process in background (with an ampersand at the end of the command) and redirecting stdout to a file.
To my surprise, that doesn't work. As soon as I close the Putty window, the process is stopped.
How can I prevent that from happening??
Source: (StackOverflow)
I've recently heard a few people say that in Linux, it is almost always better to use processes instead of threads, since Linux is very efficient in handling processes, and because there are so many problems (such as locking) associated with threads. However, I am suspicious, because it seems like threads could give a pretty big performance gain in some situations.
So my question is, when faced with a situation that threads and processes could both handle pretty well, should I use processes or threads? For example, if I were writing a web server, should I use processes or threads (or a combination)?
Source: (StackOverflow)
Does any one know how do I get the current open windows or process of a local machine using Java?
What I'm trying to do is: list the current open task, windows or process open, like in Windows Taskmanager, but using a multi-platform approach - using only Java if it's possible.
Source: (StackOverflow)
How do I find processes that listens to/uses my tcp ports? I'm on mac os x.
Sometimes, after a crash or some bug, my rails app is locking port 3000. I can't find it using ps -ef... How do I find the stupid thing and kill it, brutally... ?
When doing rails server I get
Address already in use - bind(2) (Errno::EADDRINUSE)
2014 update:
To complete some of the answers below: After executing the kill commands, deleting the pid file might be necessary rm ~/mypath/myrailsapp/tmp/pids/server.pid
Source: (StackOverflow)
I have a problem with some zombie-like processes on a certain server that need to be killed every now and then. How can I best identify the ones that have run for longer than an hour or so?
Source: (StackOverflow)
What is the technical difference between a process and a thread? I get the feeling a word like 'process' is over used and there is also hardware and software threads. How about light-weight processes in languages like Erlang? Is there a definitive reason to use one term over the other?
Source: (StackOverflow)
I am running a program and want to see what its return code is (since it returns different codes based on different errors).
I know in Bash I can do this by running
echo $?
What do I do when using cmd.exe on Windows?
Source: (StackOverflow)
I'm creating new processes using System.Diagnostics.Process class from my application.
I want this processes to be killed when/if my application has crashed. But if I kill my application from Task Manager, child processes are not killed.
Is there any way to make child processes dependent on parent process?
Source: (StackOverflow)
This question is covered here in great detail.
How do you measure the memory usage of an application or process in Linux?
From the blog article of Understanding memory usage on Linux, "ps" is not an accurate tool to use for this intent.
Why ps is "wrong"
Depending on how you look at it, ps is not reporting the real memory usage of processes. What it is really doing is showing how much real memory each process would take up if it were the only process running. Of course, a typical Linux machine has several dozen processes running at any given time, which means that the VSZ and RSS numbers reported by ps are almost definitely "wrong".
Source: (StackOverflow)
My application runs as a background process on Linux. It is currently started at the command line in a Terminal window.
Recently a user was executing the application for a while and it died mysteriously. The text:
Killed
was on the terminal. This happened two times. I asked if someone at a different Terminal used the kill command to kill the process? No.
Under what conditions would Linux decide to kill my process? I believe the shell displayed "Killed" because the process died after receiving the kill(9) signal. If Linux sent the kill signal should there be a message in a system log somewhere that explains why it was killed?
Source: (StackOverflow)
I want to make a pause between two lines of code, Let me explain a bit:
-> the user clicks a button (a card in fact) and I show it by changing the background of this button:
thisbutton.setBackgroundResource(R.drawable.icon);
-> after let's say 1 second, I need to go back to the previous state of the button by changing back its background:
thisbutton.setBackgroundResource(R.drawable.defaultcard);
-> I've tried to pause the thread between these two lines of code with:
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
However, this does not work. Maybe it's the process and not the Thread that I need to pause?
I've also tried (but it doesn't work):
new Reminder(5);
With this:
public class Reminder {
Timer timer;
public Reminder(int seconds) {
timer = new Timer();
timer.schedule(new RemindTask(), seconds*1000);
}
class RemindTask extends TimerTask {
public void run() {
System.out.format("Time's up!%n");
timer.cancel(); //Terminate the timer thread
}
}
}
How can I pause/sleep the thread or process?
Source: (StackOverflow)
UPDATE: Since this post has gotten a lot of attention over the years, I've listed the top solutions per platform at the bottom of this post.
Original post:
I want my node.js server to run in the background, i.e.: when I close my terminal I want my server to keep running. I've googled this and came up with this tutorial, however it doesn't work as intended. So instead of using that daemon script, I thought I just used the output redirection (the 2>&1 >> file part), but this too does not exit - I get a blank line in my terminal, like it's waiting for output/errors.
I've also tried to put the process in the background, but as soon as I close my terminal the process is killed as well.
So how can I leave it running when I shut down my local computer?
Top solutions:
Source: (StackOverflow)
I keep getting this error during the build of my VS2012 C# project
Error 41 Could not copy "obj\Debug\WeinGartner.WeinCad.exe" to
"bin\Debug\WeinGartner.WeinCad.exe".
Exceeded retry count of 10. Failed.
Error 42 Unable to copy file "obj\Debug\WeinGartner.WeinCad.exe" to
"bin\Debug\WeinGartner.WeinCad.exe". The process cannot access the file
'bin\Debug\WeinGartner.WeinCad.exe' because it is being used by another
process.
Now I've figured out that killing the process
Weingartner.WeinCad.vhost.exe
works (sometimes ) but this is getting on my nerves. Any way to stop this happening at all?
My debugger settings are
Source: (StackOverflow)
I'm trying to port a shell script to the much more readable python version. The original shell script starts several processes (utilities, monitors, etc.) in the background with "&". How can I achieve the same effect in python? I'd like these processes not to die when the python scripts complete. I am sure it's related to the concept of a daemon somehow, but I couldn't find how to do this easily.
Source: (StackOverflow)