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

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The TIME field in ps -ef

When I do ps -ef, I see "TIME" field. What does this field mean? From what I understand, this tells the actual CPU time, that the process got (amidst all the context switching). Does the TIME field ...
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How to see complete list of processes in top

When I do 'top', I learn that there are many processes running out of which many are in sleep state. I need to see complete snapshot of all processes at that point. the 'top' is able to show listing ...
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How to know reason of a process going to sleep state and wake it up?

When I do 'top' , I see my perl script process in 'S' state. Is there a way to know, what is making this perl process go in sleep state and ways to wake it up? Any way to debug to give more insights ...
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939 views

Need help with understanding output of ps -ef on linux

When I do ps -ef on my Linux box, I get: UID PID PPID C STIME TTY TIME CMD Please help me with meaning of C,TIME. is the TIME , the actual cpu time allocated to the process?
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144 views

How do you prevent user from opening a program?

I'm trying to write a script which prevents the concerned user from opening programs (mostly internet browsers) from being run during a certain time (like 1000 to 1200 hrs). This is like a ...
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280 views

What's the best strategy to catch mystery process?

I have running processes on my server that get killed every night at midnight. It's at work, I'm not around when it happens and I don't have remote access. The kill occurs very predicably at 23:59 ...
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698 views

Why is there a type for process ids (pid_t), but not for file descriptors (fd)?

I see that pid_t is typedef'd in unistd.h, and file descriptors are defined to be int in fcntl.h. But since they are used in similar ways, wouldn't it make sense to have a typedef for file ...
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192 views

Set a callback for when a certain process is spawned

The script I'm writing launches process A, which after an uncertain amount of time, launches a child process B. I need the script to execute a command C which depends on process B. But B might not be ...
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Kill all process of users in Ubuntu?

How to kill all process of one user? When I make ps aux I obtain a list of process with several users, and I want to kill all process of user name1 for example! What's a command to do that in Ubuntu? ...
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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 an example output: 02:34:36 PM PID minflt/s ...
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137 views

Get process list with logical intersection of selectors?

The Linux ps command allows multiple selectors, such as user and command name, but always returns the logical OR of those selectors (more than I want). Does anyone know of a method or tool already ...
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451 views

Process Migration Scripting

I want to write some shell script which can perform the process migration from one node to another. Is it possible ? Can somebody please help me scripting this. What all should I know before coding ...
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Preventing program from using internet

Is there a way to block certain programs from being able to connect to the internet in Debian (a firewall blocking outgoing connections), so for example, to block a windows program running in wine ...
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465 views

Redirecting/grep'ing an existing shell's STDOUT

I run a lot of long running processes (simulations) that print progress to STDOUT. I occasionally forget to redirect to STDOUT to a file I can grep, and it's usually too far along to restart. ...
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2answers
508 views

Force change of a user's cwd as root

I'm looking to change a user's process such that I can set it's cwd. Related, and secondary to the question, I have a filesystem I want to unmount but a user is sitting on it with a bash process. I ...
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How to kill a ghost process? AIX 6.1

oslevel: 6100-05-01-1016 according to topas: root 1769602 1 93 20 112 0 128 32498:07 87.1 0 0 ldmp_pro according to ps: -bash-4.1# ps -ef | egrep -i "1769602|ldmp" ...
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How is /proc/self implemented in Linux?

I was tinkering around with the /proc filesystem in Linux, and I came across /proc/self, which is a symbolic link to the process directory of the current process. I would like to know how it is ...
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How often is PSS value updated for a given process in /proc/pid/smaps

So if n processes are sharing a library L with size M then the contribution to their PSS is M/n. Now imagine one of the process terminates. So the contribution would be M/(n-1). Q1: My question is ...
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980 views

How to track file change

nsswitch.conf file always corrupts somehow. I do restore from my backup every time it corrupt. When this file corrupts, its time stamp is changing. Now I wonder if there is a way to track that file ? ...
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Write inside a socket open by another process in Linux

Is it possible on Linux for a process to write inside a socket open by another one? Let's say I open a connection to google.com using netcat: myuser@linux:~$ nc google.com 80 Now I can lookup for ...
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Is there a way to identify which process turns into Zombie process

One of the ubuntu server has 82 zombie processes. All processes shows '[sh] defunct' as process command. Is there a way to find out which process is becoming a zombie process? I tried checking the ...
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98 views

Command to list in real time all the actions of a process

I cannot remember this command (and googling was unsuccessful), but there is a way to get the list of actions performed by a process, that outputs something like # listprocessactions -p 1234 ...
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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 ...
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Graceful way to kill process

After my bash script is done with the selenium server, the script kills it like this: kill `ps -ef | grep selenium | awk '{ print $2 }'` While this works and it does kill the selenium script, it ...
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Is the sum of all PIDs “utime” the total system utime?

In order to measure a user's total CPU time, I'm using the "utime" field out of /proc/[pid]/stat: utime %lu Amount of time that this process has been scheduled in user mode, measured in ...
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How can I send data to the STDIN of a background process?

I'm trying to: Launch several ssh sessions (processes) through a script (Python) Communicate with the sessions by sending them commands via STDIN (even though they aren't open in my current ...
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Apache cannot fork: cannot allocate memory

I am running apache on Fedora with mod_perl. The server forks a process to send an email frequently - and the fork exits. Suddenly, I got: Cannot fork: Cannot allocate memory. There was plenty of ...
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How to stop a program running as daemon

I have launched iperf in daemon mode with iperf -s -D and now I want to stop the service. I tried to use sudo kill pid but it neither work nor complain. The daemon is still running when I check ...
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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 ...
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727 views

Cross-platform (Linux, BSD, Solaris) way to check if pid exists

I am looking for a reliable cross-platform way to check if a process with a specific pid is running. Two possible solutions came up: kill -0 $PID — exit status is 0 if it the process exists and 1 ...
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Are kernel threads really kernel processes?

I've read in many places that Linux creates a kernel thread for each user thread in a Java VM. (I see the term "kernel thread" used in two different ways: a thread created to do core OS work and a ...
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How does forking affect a process's memory layout?

Please see the following figure showing the memory layout of a process: : When someone forks(), and a new task_struct is assigned, what happens to the addresses of the process? In more or less other ...
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Why is my C++ program killed by OS

I've compiled small C++ application for school project on my virtual ubuntu 11.04. However when I attempt to run it over some larger data set after ~20 sec the program is killed by OS. Killed ...
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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 ...
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Unkillable apache2 processes

After upgrading from debian lenny to squeeze (apache2 2.2.16-6+squeeze4 and php 5.3.10-1~dotdeb.1), my apache processes started to exit with segmentation fault. It happens every 5-30 minutes (for 1 ...
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Maintain 100 instances of a program running

I'm currently using supervisord to maintain 100 instances of a script running at once. If any die then it starts up a new one. However it seems to be struggling maintaining larger numbers (>300 ...
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Detecting whether a server is loaded

I have to start some performance test on a Rhel 6 box, but before starting the test, i have to make sure there are no other java processes running. The manual way of doing it would be to use "ps -ef ...
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1answer
758 views

How can I manage jobs after I disconnect from my tty/ssh session?

If I ssh to a box and start a task that will take some time to complete I usually press control+z to pause the process, and then immediately type bg 1 to put run it in the background. I can then type ...
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How to read environment variables of a process

Linux's /proc/<pid>/environ does not update (as I understand it, the file contain the initial environment of the process). How can I read a process's current environment?
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killing processes automatically

I need to kill all processs in a certain shell excluding certain processes. Like sh which is my shell. And the comand. This is what currently in my shell right now. rcihp146 :/home/msingh2> ps ...
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When you try to terminate a process for good, which option for “kill” should you use?

I am getting a lot of mixed messages from people, and was wondering if it there really is not much of a difference in what you use. kill 'x' killall 'x' kill -9 'x' These are some options I've been ...
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Is it the process that cleans itself on termination or the kernel?

Recently I found this in a powerpoint presentation: When a program is compiled and linked, the linker inserts some extra code in the program. It is this code that calls the main function about the ...
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What is meant with terminating a process normally?

In an examination it is stated: Give 2 different ways that a process can terminate normally. Describe the differences. What is meant with terminate normally?
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How to kill a daemon with its name gracefully?

I usually kill a process with killall. killall markdoc But I am not sure if this command terminates the process gracefully. Does this command achieve graceful termination? If it does not, how can ...
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3answers
5k views

If I see a process running using ps, how can I find the executable?

If I can see a process running using ps -e, how can I find the file which launched it?
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1answer
240 views

Why is the following command killing a system?

Anyone understand the following code , running in bash ? :(){ :|:& };: It seems to be a "fork" bomb on Linux.
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173 views

Alert when a process exits

I often download files using wget and cURL. Is there anyway I can make my Linux box give a visual alert when either of those processes exit (i.e: the download completes) PS : I am using Ubuntu ...
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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.: ...
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Finding the ID of a process and killing it

When ever I need to kill a background process I do ps -e | grep <process_name> Which prints something like this 1766 ? 00:00:13 conky , Then I use the process ID to kill it like so kill 1766 . ...
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Limit process resource consumption in CentOS 5 (2.6.18 kernel)

I would like to limit the resource (CPU, Memory, and network bandwidth) consumption of processes on the same server. And it will be good if I can migrate processes from one server to another. I ...