A process is an instance of a computer program that is being executed.

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How to stop a background process?

I have started a wget on remote machine in background using &. Suddenly it stops downloading. I want to stop its process, then start it again. How can I stop it? I haven't close its shell window. ...
29
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1answer
27k views

Getting information about a process' memory usage from /proc/pid/smaps

For a given process in /proc/<pid>/smaps, for a given mapping entry what are: Shared_Clean Shared_Dirty Private_Clean Private_Dirty Is Shared_Clean + Shared_Dirty the amount of memory that ...
36
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4answers
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How to attach terminal to detached process?

I have detached a process from my terminal, like this: $ process & That terminal is now long closed, but process is still running and I want to send some commands to that process's stdin. Is ...
51
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3answers
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Find out current working directory of a running process?

What command(s) can one use to find out the current working directory (CWD) of a running process? These would be commands you could use externally from the process.
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4answers
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Why do we need to fork to create new processes?

In Unix whenever we want to create a new process, we fork the current process, creating a new child process which is exactly the same as the parent process; then we do an exec system call to replace ...
33
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7answers
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Is there a way to see details of all the threads that a process has in Linux?

For Windows, I think Process Explorer shows you all the threads under a process. Is there a similar command line utility for Linux that can show me details about all the threads a particular process ...
24
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7answers
12k views

Is there a way to limit the amount of memory a particular process can use in Unix? [duplicate]

I need to test a process for memory management. I do not have the source, so I need to do all the testing from the OS side. I want to be able to say something like limitmemory 400k -p <pid> ...
12
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2answers
4k views

how to find out namespace of a particular process?

I already asked a question about how to list all namespaces in Linux, but there wasn't any correct and exact answers, so I want to find out a method which can help me to find out the namespace of PID ...
16
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1answer
26k views

What does this process STAT indicates?

If you check the STAT column in above image you will see Ss S S< SN and R+ What does this indicates ? Process states. If yes,Then what is the significance of 'Ss S< SN and R+'?
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1answer
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How to see process created by specific user in Unix/linux

I want to see list of process created by specific user or group of user in Linux Can I do it using ps command or is there any other command to achieve this?
21
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2answers
4k views

What happens when we type a simple command on shell? [duplicate]

I have a simple doubt on execution of a simple command. As per my understanding, when we type a command such as ls on interactive shell, Shell interpretes the command. Shell creates a child process ...
13
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2answers
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Linux: Writing a watchdog to monitor multiple processes

A few years ago, a coworker came up with an elegant solution for a watchdog program. The program ran on Windows and used Windows Event objects to monitor the process handles (PID’s) of several ...
21
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Use & (ampersand) in single line bash loop

I have been using this command successfully, which changes a variable in a config file then executes a Python script within a loop: for((i=114;i<=255;i+=1)); do echo $i > numbers.txt;python ...
6
votes
3answers
85k views

How can I see what processes are running?

I use Ubuntu Server 10.10 and I would like to see what processes are running. I know that PostgreSQL is running on my machine but I can not see it with the top or ps commands, so I assume that they ...
4
votes
1answer
1k views

Difference between process group and job?

What's the difference between a process group and a job? If I type pr * | lpr then is it both a process group as well a job? What exactly is the difference between a process group ID and a job ID? ...
16
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3answers
4k views

Can I limit a process to a certain amount of time / CPU cycles?

We have a script which runs on our web servers, triggered by customer action, which initiates a unix process to generate some cache files. Because this process acts upon files supplied by our ...
14
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3answers
8k views

If you ^Z from a process, it gets “stopped”. How do you switch back in?

I accidentally "stopped" my telnet process. Now I can neither "switch back" into it, nor can I kill it (it won't respond to kill 92929, where 92929 is the processid.) So, my question is, if you have ...
9
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2answers
4k views

How to kill both process and subprocess?

I asked a question to know how to get multiple lines of message from Python's subprocess module. The problem is that in the course of testing, I had to kill the python process that runs gnuchess ...
6
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3answers
6k views

How to check how long a process ran after it finished?

Currently I'm using the following to check how long a process is actually running: ps -eo uid,pid,etime | egrep '^ *MY_ID' | egrep 'PID_OF_PROCESS' And that outputs the following: MY_ID ...
3
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3answers
2k views

Discrepancy between reported used memory and sum of application memory usage

I'm running a desktop system that quite regularly suffers from lack of memory, this prompted me to investigate what causes the issue in the first place. Problem is, there's no single process that ...
8
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1answer
417 views

What three files are always opened by a process?

Someone mentioned that there are three different files that a process always opens. What does this mean? What files are they?
6
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2answers
3k views

Why Process/program becomes zombie?

If script is running fine from command line then, why the same script becomes zombie state after running through cron and How you will troubleshoot the same ? Here following real example : [root@abc ...
6
votes
1answer
6k views

Find processes using a network interface

I'm trying to find a way to safely shutdown a network interface, i.e. without disturbing any processes. For this I need to find out what processes are currently using that interface. Tools like ss, ...
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2answers
176 views

Absolute path to currently-running zsh?

Sometimes the output of ps -p $$ shows the absolute path to the currently-running zsh, % ps -p $$ PID TTY TIME CMD 1027 ttys005 0:00.11 /usr/local/bin/zsh but not always: % ps -p ...
2
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1answer
774 views

Check for process already running in webfaction?

I use Django framework on webfaction and have 5 different cron jobs. One of them lasts much longer than others and sometimes gets stuck (30-120 seconds or more). I have already set that cron job to ...
2
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2answers
1k views

How can I make a process I start during an SSH session run after the session has ended? [duplicate]

Possible Duplicate: Keep SSH Sessions running after disconnection. I have a process which is basically a web-server, I start it during an SSH session. However, when I leave the session (by ...
8
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5answers
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Drop Process Privileges

I have a process that gets started by a damon running as root, now I want to "downgrade" this process's privileges to those of your average user. Is this possible? If yes how? PS: Running unix on a ...
7
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4answers
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monitoring file changes + process access to files

I would like to see what's happening in my app server folders, which files are changed by process x or which *.war files has been changed (replaced/created) in last x minutes. I am software developer ...
5
votes
2answers
76 views

Suspend process without killing it

So I've got a persistent program running in the background. Killing it just causes it to restart with a different PID. I'd like to suspend it (put it to sleep without actually killing it). Does kill ...
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2answers
1k views

Removing zombie process from the process table

Can somebody please explain when parent process receives the exit status of a dead child process via wait, who actually reallocates the memory of the child process and removes it from the process ...
3
votes
3answers
6k views

Cron job to check if PHP script is running, if not then run

I am wondering if someone might point me in the right direction. I've got little experience working with the Linux command line and recently due to various factors in work I've been required to gain ...
3
votes
2answers
189 views

How to find out the reason a command/code was executed on Linux?

I have a complex embedded Linux software running on a gentoo derivative, on which a certain piece of code gets executed regularly every ~84 minutes. Sweeping through the main code to find places where ...
3
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2answers
3k views

Why doesn't stopping the nginx server kill the processes associated with it?

When I stop nginx like this on ubuntu 12.04, I get the following errors: $ sudo service nginx stop Stopping nginx: nginx. $sudo service nginx start Starting nginx: nginx: [emerg] bind() to 0.0.0.0:80 ...
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5answers
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How to get a process uptime under different OS?

Under Linux I can get a process's uptime in seconds with: echo $(($(cut -d "." -f1 /proc/uptime) - $(($(cut -d " " -f22 /proc/$PID/stat)/100)))) But how can I get it under different OS? ex.: ...
2
votes
1answer
212 views

iotop showing 1.5 MB/s of disk write, but all programs have 0.00 B/s

I don't understand iotop output: it shows ~1.5 MB/s of disk write (top right), but all programs have 0.00 B/s. Why? The video was taken as I was deleting the content of a folder with a few millions ...
2
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3answers
3k views

Why does Firefox refuse to die despite killing it with pkill -9?

I am issuing the following command to kill Firefox on my Red Hat Linux box: [subhrcho@slc04lyo ~]$ pkill -9 -f firefox [subhrcho@slc04lyo ~]$ However, when I try to invoke Firefox through ...
2
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2answers
2k views

How to pass data outside process for zenity progress?

Usually this would be a question about how to pass data from a subprocess to a main process, but maybe zenity has some extra quirks so please focus on zenity. Example: #!/bin/sh ( echo "10" ; sleep ...
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2answers
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what is a background process?

Here is a common definition of a background process: "A background process is a program that is running without user input. A number of background processes can be running on a multitasking operating ...
38
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2answers
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Limit process to one cpu core

How to limit process to one cpu core ? Something similar to ulimit or cpulimit would be nice. (Just to ensure: I do NOT want to limit percentage usage or time of execution. I want to force app (with ...
30
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6answers
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Is there a program that can send me a notification e-mail when a process finishes?

I am a computational scientist, and I run a lot of lengthy calculations on Linux. Specifically, I run molecular dynamics (MD) simulations using the GROMACS package. These simulations can take days ...
21
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6answers
8k views

Can ps display only non kernel processes on Linux?

How can I ask ps to display only user processes and not kernel threads? See this question to see what I mean...
33
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2answers
4k views

Why is the default process creation mechanism fork?

The UNIX system call for process creation, fork(), creates a child process by copying the parent process. My understanding is that this is almost always followed by a call to exec() to replace the ...
24
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3answers
3k views

How can I see the exact command line being executed inside some bash instance?

I have a long running bash instance (inside a screen session) that is executing a complex set of commands inside a loop (with each loop doing pipes, redirects, etc). The long command line was ...
46
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6answers
125k views

How to find which processes are taking all the memory?

I'm looking for somthing like top is to CPU usage. Is there a command line argument for top that does this? Currently, my memory is so full that even 'man top' fails with out of memory :)
20
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8answers
40k views

Kill many instances of a running process with one command

This is one of the questions that has troubled me often. Suppose I have thousand or more instances of any process(for e.g. say the process vi) running. How do I kill them all in one single shot/one ...
24
votes
2answers
9k views

When was a process started

To know when was a process started, my first guess was to check the time when /proc/<pid>/cmdline was written/modified the last time. ps also shows a START field. I thought both of these ...
21
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3answers
27k views

Where can I see a list of kernel killed processes?

Is there some way I can check which of my processes the kernel has killed? Sometimes I log onto my server and find that something that should've run all night just stopped 8 hours in and I'm unsure if ...
18
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1answer
8k views

init process: ancestor of all processes?

I have always learned that the init process is the ancestor of all processes. Why does process 2 have a PPID of 0? $ ps -ef | head -n 3 UID PID PPID C STIME TTY TIME CMD root ...
16
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4answers
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Why is SIGINT not propagated to child process when sent to its parent process?

Given a shell process (e.g. sh) and its child process (e.g. cat), how can I simulate the behavior of Ctrl+C using the shell's process ID? This is what I've tried: Running sh and then cat: ...
26
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3answers
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If processes inherit the parent's environment, why do we need export?

I read here that the purpose of export in a shell is to make the variable available to sub-processes started from the shell. However, I have also read here and here that "Processes inherit their ...