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

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Limiting processes by memory under Linux

We must launch several hungry processes on a Linux system. These processes often need several Go (~5Go) of memory to run (total memory: 16Go RAM + 2Go swap). At first, when the system was running ...
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Why are there so few “running” processes?

On all of BSD/Linux/MacOS and Solaris, I made an observation - no matter how busy the system is, top always reports very few (usually 1-2) running processes. According to my limited understanding, a ...
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Why do top and ps show different PIDs for the same processes?

When I run top -H, I see that my multiple mysql threads all have the same PID. However, in ps -eLf I see each one has a different PID: ps -eLf UID PID PPID LWP C NLWP STIME TTY ...
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How can I allow a user to prioritize a process to negative niceness?

I want a user to run a specific process on the system with a negative nice value. I can't simply fork the process to background as this specific program is a minecraft server and I rely on the command ...
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Which system calls could create a new process?

When executing ps command in my Linux system i see some user processes twice (different PID...). I wonder if they are new processes or threads of the same process. I know some functions in standard C ...
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Using `kill -s 0 $pid` vs `[[ -e /proc/$pid ]]` to detect if PID is running

One of the idioms often used to check if process is running is to use kill -s 0 $pid. My question is, does it have any upsides over using [[ -e /proc/$pid ]] construct? The script I'm writing is ...
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Get the PID of file creation

I am writing a bash script that creates 5 files with the extension ".P" and write a line of "something" into them. "P" represents a number and it's the PID of the process that creates the file. How ...
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Difference between process in background and daemon [duplicate]

What is technically the difference of a process that started in foreground and was manually put into background and a daemon? Do they have different properties?
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What is the rtsbpp-polling process doing?

In Ubuntu 12.04 LTS when I run the top command I see a process called rtsbpp-polling. Googling it gives only just a few hits to the Gentoo Linux forum that does not seem to be relevant (they don't ...
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If computers start counting at 0, why does the init process have a pid of 1?

Not much to put here in the body, the question is self explanatory.
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How to send a running process to jail?

"Go directly to jail; do not pass go, do not collect $200" — Monopoly Is there any way to make a running process's all future file access behave as if it has always been in a chroot environment?
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365 views

Grep Wvdial output while it is running

I want to grep the output from wvdial while wvdial is running. Actually I want to fire a task when the modem is connected. I want to do this in the following way: grep string "IP address", if it is ...
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What information about a process is retrievable after it is terminated? [duplicate]

After a process has been terminated, is it possible to retrieve any information about it, such as when it started and finished, &c. Is it possible to enable logging of this information?
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Can I somehow add a “&& prog2” to an already running prog1?

Most shells provide functions like && and ; to chain the execution of commands in certain ways. But what if a command is already running, can I still somehow add another command to be executed ...
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Is it possible to control xterm (or specifically a process that xterm has started) from another process?

If I start a process with xterm like this (where omxplayer is the process xterm is starting): xterm -fullscreen -fg black -bg black -e omxplayer -o hdmi -r %f Is it possible for me to write to ...
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AIX open() : file descriptor is zero (!?)

A daemon process, on detecting the presence of a text file in a particular directory then launches an executable file which opens the aforementioned text file in order to read and then transmit its ...
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How do I print the process name next to the process ID number in a file?

I'm redirecting results for something into a file and I also need to find the process name and ID number and redirect it to the file as well. I'm guessing the process name is the command in which I'm ...
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Modify 'Soft Limit' of 'Max processes'

I tried ulimit -u 2000 and ulimit -Su 2000 to modify the 'Max processes', and started up my program, but failed. I found file '/proc/pid/limit' is still: Max processes 1024 ...
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accessing stdin/stdout of a process started in another tty

I logged in to my linux physically(say tty1) and started a process that watches stdin for commands and has some stdout-put. How can I access/use this process from a SSH session?
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How to identify a process which has no pid?

I have a process which listen to 2 ports : 45136/tcp and 37208/udp (actually I assume it is the same process). But netstat doesn't return any pid : netstat -antlp | grep 45136 tcp 0 0 ...
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Detecting kernel thread on pre-3.0 kernels

Looking at the proc man page (http://man7.org/linux/man-pages/man5/proc.5.html) it is possible to detect which processes are kernel threads in /proc/<pid>/stat by looking at the flags value ...
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lsof - debug the output information

I was going through the questions of this site. In this particular question, I see the command lsof being used to list the files that are open for a particular user. I ran the below command in my ...
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Bind9 — How to find which programs are making which dns lookups?

Using bind9 on a laptop shows lots of nonsense domains when network connectivity is down: Oct 18 19:56:18 lap3 named[1536]: error (network unreachable) resolving './NS/IN': 128.63.2.53#53 Oct 18 ...
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Processes in Linux

As I understand it, process descriptors are stored in a doubly linked list data structure. But a fork can create multiple children for the same process, so that makes me think that there is a tree ...
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Is there a way to really prioritize processes or make Linux respect their priorities?

I know there are process priorities like in other operating systems, going from -20 (most prio) to 19 (less prio) but Linux seems to ignore them. Right now I was building the kernel in the background ...
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How to make processes not die after its parent dies?

I've been messing with forkbombs and noticed that if I just fork() processes repeatedly, killing the initial process will bring down the whole tree. This is not the case for forkbombs written in BASH ...
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process id and killing process - ps commmand

Please see the output of below ps command: abc@smaug:~/Desktop$ ps ax | grep firefox 2213 ? Sl 2:01 /usr/lib/firefox/firefox 2644 pts/0 S+ 0:00 grep --color=auto firefox Please ...
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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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How does a process handle the situation when it finds no memory to use?

What happens when a particular process finds that there is no memory to use? Will that process kill/restart another process to proceed their task ? Or what the process (that requires more memory) ...
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129 views

devilspie detect if application was started with a flag

How can I set devilspie to detect if an application was started with the flag --hello-world from terminal? For example window_name detects the window title. How can transform in devilspie the ...
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150 views

ssh targetHost &; fg - does not work, but why?

I was trying the following combination in order to get the pid of the ssh session (running in the background displays the pid) and than fg to get back to the ssh session and introduce the password: ...
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KDE becomes slow

I experience problems with KDE 4.11.1 on Arch Linux. It suddenly becomes laggy and unresponsive and just as suddenly returns to the normal state after some time. Normal CPU load (KSysGuard): ...
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child process does not inherit the pending signals from the parent after a fork system call, why?

Could anybody please tell me the reason to why pending signals are not inherited by the child process? On the other hand, the child process inherits the signal handlers and signal mask from the ...
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How to monitor top applications using CPU (and IO if possible) in a graph?

I need to find what and when these applications used so much CPU (and IO if possible too). This should be in a graphic timeline like we see in GNOME System Monitor CPU History. I also want to compare ...
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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 ...
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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 ...
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What's the difference between pkill and killall?

I know that pkill has more filtering rules than killall. My question is, what is the difference between: pkill [signal] name and killall [signal] name I've read that killall is more effective ...
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How can I recover suspended processes after restarting X?

I had several instances of Firefox running, which I suspended. I think I used 'the GUI' (KDE's System Activity), which I think is the same as kill -19. Normally this works fine - I can resume the ...
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UNIX- Identify which processes are running more that 6hours

I need to know which processes are running more than 6 hours in UNIX. How can I find those out?
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bash: Run command in background and capture pid [duplicate]

Am writing a bash 4.1 script... Would like run another script (or internal function) in the background... And capture the pid of that background job in a variable in the foreground script... If the ...
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How can I automatically kill the process with the highest CPU load?

Sometimes programs will lock up in the background and cause high CPU usage. Is there any way I can programmatically ascertain which process is causing the highest CPU load at the moment and kill it?
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Wait for background processes to finish with inverse match process ID

I'm looking to run a number of background processes in a loop, but only want to wait for all of those processes to finish, still allowing another background process to continue. After doing some ...
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Why is a user started process running when not logged in?

Following a tutorial on setting up gnupg to manage ssh keys I've managed to get several instances of gpg-agent running: [root@frylock ~]# ps aux | grep agent root 2764 0.0 0.0 4208 432 ? ...
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LD_PRELOAD or similar to prevent network access

I'd like to start a program disconnected from the network (because immediately upon starting it tries to download huge amounts of data, which can be prevented by changing settings as soon as it ...
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495 views

Find PHP process that logs to file

I have started a PHP script via browser and due to a loop error the script continues to be executed even after closing the browser. I am noticing it since the script is logging error messages to my ...
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How to list killable tasks?

As manpage of ps states A process with STATUS with the value "D" means "uninterruptible sleep (usually IO)" Also, I've read: You should use TASK_INTERRUPTIBLE here, otherwise your kernel thread ...
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how to stop kernel threads preempting real time user space processes?

I created some processes in user space and tried to visualize its working in kernelshark with the trace recorded using trace-cmd. But kernel processes like the ones shown below are preempting my ...
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Get return value of process by PID

If I have the PID of a process that was killed, how might I get the return status of the process? I am particularly interested to know if the return status was 143 (kill) or 137 (kill -9) as I don't ...
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How to send keystrokes (F5) from terminal to a process?

I'm using an Raspberry Pi in combination with Chromium (kiosk mode) to show up some stats. The Pi doesn't have an connected keyboard so I searched for a solution to send keystrokes from the terminal ...
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Is there a way to see which process invoked a shell script?

Is there a possibility so see from some unix log file what process have invoked a bash/ksh shell script or is this shell script invoked manually from command line? So is there some log file which ...