Questions tagged [process]

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

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538
votes
14answers
632k views

What if 'kill -9' does not work?

I have a process I can't kill with kill -9 <pid>. What's the problem in such a case, especially since I am the owner of that process. I thought nothing could evade that kill option.
506
votes
6answers
989k views

Finding the PID of the process using a specific port?

I am installing hadoop on my Ubuntu system. When I start it, it reports that port 9000 is busy. I used: netstat -nlp|grep 9000 to see if such a port exists and I got this: tcp 0 0 ...
383
votes
11answers
515k views

How can I run a command which will survive terminal close?

Sometimes I want to start a process and forget about it. If I start it from the command line, like this: redshift I can't close the terminal, or it will kill the process. Can I run a command in such ...
304
votes
4answers
377k views

How to get the pid of the last executed command in shell script?

I want to have a shell script like this: my-app & echo $my-app-pid But I do not know how the get the pid of the just executed command. I know I can just use the jobs -p my-app command to grep ...
281
votes
12answers
439k views

How to view the output of a running process in another bash session?

I have left a script running on a remote machine from when I was locally working at it. I can connect over SSH to the machine as the same user and see the script running in ps. $ ps aux | grep ...
269
votes
10answers
388k views

How to check how long a process has been running?

I would like to avoid doing this by launching the process from a monitoring app.
249
votes
11answers
681k views

How to terminate a background process?

I have started a wget on remote machine in background using &. Suddenly it stops downloading. I want to terminate its process, then re-run the command. How can I terminate it? I haven't closed ...
235
votes
12answers
391k views

How to monitor CPU/memory usage of a single process?

I would like to monitor one process's memory / cpu usage in real time. Similar to top but targeted at only one process, preferably with a history graph of some sort.
222
votes
3answers
108k views

Why does `htop` show more process than `ps`

In ps xf 26395 pts/78 Ss 0:00 \_ bash 27016 pts/78 Sl+ 0:04 | \_ unicorn_rails master -c config/unicorn.rb 27042 pts/78 Sl+ 0:00 | ...
209
votes
5answers
172k views

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.
194
votes
2answers
325k views

There are stopped jobs (on bash exit)

I get the message There are stopped jobs. when I try to exit a bash shell sometimes. Here is a reproducible scenario in python 2.x: ctrl+c is handled by the interpreter as an exception. ctrl+z 'stops'...
154
votes
5answers
138k views

How do I read from /proc/$pid/mem under Linux?

The Linux proc(5) man page tells me that /proc/$pid/mem “can be used to access the pages of a process's memory”. But a straightforward attempt to use it only gives me $ cat /proc/$$/mem /proc/self/...
140
votes
3answers
275k views

Find and remove large files that are open but have been deleted

How does one find large files that have been deleted but are still open in an application? How can one remove such a file, even though a process has it open? The situation is that we are running a ...
135
votes
2answers
387k views

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?
123
votes
5answers
178k views

How do I attach a terminal to a 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 ...
122
votes
10answers
482k views

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 ...
117
votes
3answers
158k 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 ...
114
votes
7answers
59k views

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 ...
104
votes
5answers
197k views

Determining what process is bound to a port

I know that using the command: lsof -i TCP (or some variant of parameters with lsof) I can determine which process is bound to a particular port. This is useful say if I'm trying to start ...
101
votes
9answers
354k 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 :)
94
votes
12answers
226k views

Kill many instances of a running process with one command

Suppose I have a thousand or more instances of any process (for example, vi) running. How do I kill them all in one single shot/one line command/one command?
94
votes
7answers
143k views

How do I find out which processes are preventing unmounting of a device?

Sometimes, I would like to unmount a usb device with umount /run/media/theDrive, but I get a drive is busy error. How do I find out which processes or programs are accessing the device?
94
votes
5answers
30k views

What process created this X11 window?

Given an X11 window ID, is there a way to find the ID of the process that created it? Of course this isn't always possible, for example if the window came over a TCP connection. For that case I'd ...
92
votes
3answers
16k views

How does Linux “kill” a process?

It often baffles me that, although I have been working professionally with computers for several decades and Linux for a decade, I actually treat most of the OS' functionality as a black box, not ...
88
votes
3answers
41k views

What are “session leaders” in `ps`?

What are session leaders, as in ps -d which selects all processes except session leaders?
87
votes
4answers
2k views

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 ...
87
votes
11answers
53k views

Block network access of a process?

Is it possible to block the (outgoing) network access of a single process?
87
votes
9answers
36k views

How can I check what signals a process is listening to?

How can I verify whether a running process will catch a signal, or ignore it, or block it? Ideally I'd like to see a list of signals, or at least not have to actually send the signal to check.
87
votes
5answers
52k views

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 ...
86
votes
5answers
149k views

Kill all descendant processes [duplicate]

I'm writing an application. It has the ability to spawn various external processes. When the application closes, I want any processes it has spawned to be killed. Sounds easy enough, right? Look up ...
84
votes
6answers
139k views

How to get whole command line from a process?

How can I get the command arguments or the whole command line from a running process using its process name? For example this process: # ps PID USER TIME COMMAND 1452 root 0:00 /sbin/...
80
votes
3answers
41k views

What does `kill -0` do?

I recently came across this in a shell script. if ! kill -0 $(cat /path/to/file.pid); then ... do something ... fi What does kill -0 ... do?
79
votes
2answers
96k views

How to limit a process to one CPU core in Linux? [duplicate]

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 ...
77
votes
9answers
211k views

How to view a specific process in top

Are there any relatively strightforward options with top to track a specific process? Ideally by identifying the process by a human readable value? e.g. chrome or java. In other words, I want to view ...
76
votes
4answers
39k views

Use & (ampersand) in single line bash loop

I have been using this command successfully, which changes a variable in a config file and then executes a Python script within a loop: for((i=114;i<=255;i+=1)); do echo $i > numbers.txt; python ...
75
votes
5answers
57k views

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: [user@...
74
votes
2answers
19k views

Process with weird random name consuming significant network and CPU resources. Is someone hacking me?

In a VM on a cloud provider, I'm seeing a process with weird random name. It consumes significant network and CPU resources. Here's how the process looks like from pstree view: systemd(1)───...
73
votes
7answers
28k views

Are threads implemented as processes on Linux?

I'm going through this book, Advanced Linux Programming by Mark Mitchell, Jeffrey Oldham, and Alex Samuel. It's from 2001, so a bit old. But I find it quite good anyhow. However, I got to a point ...
71
votes
5answers
125k views

How to determine which process is creating a file? [duplicate]

Given file path, how can I determine which process creates it (and/or reads/writes to it)?
70
votes
2answers
85k views

Need explanation on Resident Set Size/Virtual Size

I found that pidstat would be a good tool to monitor processes. I want to calculate the average memory usage of a particular process. Here is some example output: 02:34:36 PM PID minflt/s ...
69
votes
4answers
203k views

How to list processes locking file?

Using flock, several processes can have a shared lock at the same time, or be waiting to acquire a write lock. How do I get a list of these processes? That is, for a given file X, ideally to find the ...
69
votes
4answers
32k views

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 and ...
69
votes
3answers
137k views

Which process has PID 0?

I'm looking for the process started in Linux which has process ID 0. I know init has PID 1 , which is the first process in Linux, is there any process with PID 0?
68
votes
2answers
38k views

What do the brackets around processes mean?

$ ps -Awwo pid,comm,args PID COMMAND COMMAND 1 init /sbin/init 2 kthreadd [kthreadd] 3 ksoftirqd/0 [ksoftirqd/0] 5 kworker/u:0 [kworker/u:0] 6 ...
66
votes
5answers
49k views

Run multiple commands and kill them as one in bash

I want to run multiple commands (processes) on a single shell. All of them have own continuous output and don't stop. Running them in the background breaks Ctrl-C. I would like to run them as a single ...
65
votes
8answers
42k views

Who's got the other end of this unix socketpair?

I want to determine which process has the other end of a UNIX socket. Specifically, I'm asking about one that was created with socketpair(), though the problem is the same for any UNIX socket. I ...
59
votes
5answers
181k views

How can I get a full process list in solaris, without truncated lines?

Is there a way to generate a full process listing in solaris, without truncated lines? I've tried the ps command, with the following arguments: -f Generates a full listing. (...
58
votes
2answers
71k views

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 0.0....
58
votes
4answers
25k views

Save entire process for continuation after reboot

I developed an algorithm for a fairly hard problem in mathematics which is likely to need several months to finish. As I have limited resources only, I started this on my Ubuntu 12.04 (x86) laptop. ...
57
votes
3answers
14k views

Why can't I crash my system with a fork bomb?

Recently I've been digging up information about processes in GNU/Linux and I met the infamous fork bomb : :(){ : | :& }; : Theoretically, it is supposed to duplicate itself infinitely until the ...

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