Programming :: Find Number Of Child Processes (C / POSIX)?

May 26, 2010

I'm in the process of writing a program that is a server- it will accept connections and stuff, and spawn a child process for each. However, i've run into a small problem. I do NOT want to bother with keeping track of the processes unless i need to. So, i set SA_NOCLDWAIT (#ifdef) on a SIG_IGN to the SIGCHLD handler through sigaction interface. The standard says that it the kernel will then keep track of reaping zombie processes for me (a HUGE plus). However, upon receiving a SIGINT signal, i want to stop the server from accepting new connections (done), and then wait for there to be no new connections. I was thinking of just putting a loop like so:

Code:

while((wait(NULL) != (pid_t)-1) && errno != ECHILD);

However, I'm not *sure* that this will work, especially with SIGCHLD still ignored. So how can i tell if there are still child processes? I can't find any call like int getnumchld(pid_t proc); (i wish). Plus it would be inefficient to spin on that function anyway. OTOH, i would rather *NOT* have to do the same thing in a loop with a system("ps |...>file"); read(file); etc. either. Is there a way i can portably implement this feature (I was hoping i could run it on linux and the major BSDs, at least).

TO SUM IT UP:

How can i tell if a process has no child processes if i've SIG_IGN'd SA_NOCLDWAIT'd the SIGCHLD? Is there a _reasonably_ portable way to do so? I *don't* want to manually wait for EVERY process. Maybe only those still active at the time of SIGTERM, but that requires keeping track of the number of connections and whether those have terminated...

EDIT: Does anyone know if the above code *would* work, even with SIGCHLD ignored and the kernel cleaning up zombies *for* me? I checked the manpage and it doesn't say much.

EDIT1: Note that all of the processes are in the same process group and session. SO i can find them through this as well. Perhaps even setting the uid/gid and finding all processes run by that group?

EDIT2: i have an idea if the above isn't feasible. If there is no "elegant" way to do it, i could reduce the complexity by sending a SIGUSR1 to the whole process group. Each process would then set a flag telling it to send a SIGUSR1 in reply and send a SIGUSR2 when it is done executing. Then i could keep a count of signals. Maybe that would be *easier*. Or perhaps a count of all child processes and just a termination signal to decrement the counter.

View 2 Replies


ADVERTISEMENT

General :: Find All Child Processes Of A Parent Process Given To Script As Argument?

Feb 15, 2011

well i have just started with shell scripting...how to find all child processes of a parent process given to script as argument.

View 10 Replies View Related

Programming :: Memory Optimization For Child Processes?

Sep 6, 2010

I work on Linux for ARM processor for cable modem. There is a tool that I have written (as the job demands) that sends/storms customized UDP packets using raw sockets. I form the packet from scratch so that we have the flexibility to play with different options. This tool is mainly for stress testing routers.

The details are here.

I actually have multiple interfaces created. Each interface will obtain IP addresses using DHCP. This is done in order to make the modem behave as virtual customer premises equipment (vcpe).

When the system comes up, I start those processes that are asked to. Every process that I start will continuously send packets. So process 0 will send packets using interface 0 and so on. Each of these processes that send packets would allow configuration (change in UDP parameters and other options at run time). Thats the reason I decide to have separate processes.

I start these processes using fork and excec from the provisioning processes of the modem.

The problem now is that each process takes up a lot of memory. Starting just 3 such processes, causes the system to crash and reboot.

I have tried the following:- 1-I have always assumed that pushing more code to the Shared Libraries will help. So when I tried moving many functions into shared library and keeping minimum code in the processes, it made no difference to my surprise.

2-I also removed all arrays and made them use the heap. However it made no difference. This maybe because the processes runs continuously and it makes no difference if it is stack or heap?

3-I suspect the process from I where I call the fork is huge and that is the reason for the processes that I make result being huge. I am not sure how else I could go about. say process A is huge -> I start process B by forking and excec. B inherits A's memory area. So now I do this -> A starts C which inturn starts B will also not help as C still inherits A?. I used vfork as an alternative which did not help either. I do wonder why.

reduce the memory used by each independent child processes.

View 1 Replies View Related

Programming :: Creating Child Processes In A Script?

Oct 14, 2010

the wrong part of the forum but basically im working on a project and getting no where what so ever and i was wondering if i could get your help. Basically i have to create two scripts do:

The parent script which is going to:
o spawn several child processes.
o keep track of the progress of the child processes.

[code]...

View 1 Replies View Related

Programming :: Ipc Between Parent And Child Processes Using Pipe?

Oct 13, 2010

If a process forks its child and communicate with the child using pipe, do closing the write end of the pipe and terminating the writing process have the same effect?

View 3 Replies View Related

Programming :: Perl - Multiple Child Processes In Parallel?

Sep 3, 2010

I'm looking for a way in Perl to be able to take a list of servers, ssh multiple commands to it and store the results. If I do this process serially, sometimes one server will hang the whole script and if it doesn't, it still takes hours to complete.

I'm thinking what I need to do is make a parent loop that calls out a separate process that passes the server name to the child sub process and then executes all the commands I have defined in its own process. If one server 'hangs', at least that won't stop the script from doing all the other servers in the list.

I'm guessing using the fork() command would serve me best, however, all the online descriptions I have found have been vague at best.

View 4 Replies View Related

Programming :: Perl Child Processes Become Zombie On A Multi-core Processor?

Apr 11, 2011

I have written a simple script which has to find required patterns from a bunch of files ( where each file is around 2 GB each,which contain the output of seq 1 10000000000000) on an 8 core machine.I am current forking 6 child processes which run simultaneously on 6 cores of the processor & have to search for the required pattern in 6 different files & inform the parent process when a pattern is found using a PIPE.

The problem is,when a child process is done reading a text file looking for a pattern,it is becoming a zombie process.It exits cleanly when i put a $SIG{CHLD} = "IGNORE"; in the script.Can any one tell me whats going on & how do i improve the communication between child and parent processes?

Code:
#!/bin/perl
use strict;

[code]...

View 3 Replies View Related

Programming :: Creates A Child Process With Fork And, When The Child Ends, Receives The SIGCHLD Signal And Wait For Its Termination?

May 23, 2011

I have a doubt about signals in C programming. I have done this little program to explain it. It creates a child process with fork and, when the child ends, receives the SIGCHLD signal and wait for its termination.Ok, quite easy, BUT when I execute this code the SIGCHLD signal is received twice, first as an error (returns -1) and the second one to finish the child process.I don't understand the meaning of the first received signal. Why is it generated? Is the code wrong? (if you add the SIGINT and press Ctrl+C during the execution it also receives two signals instead of one)

Code: #include <stdio.h>
#include <unistd.h>
#include <string.h>

[code]....

View 4 Replies View Related

General :: Finding All Attached Child Processes

Nov 17, 2010

I want to check all the child processes attached to a specific process. Say for a example; my process is a java process. Then I wanna know what are the processes attached to that java process. At the moment I use the command # ps aux|grep java; this gives the details about the currently running java process. So I can kill the whole java process using #kill -9 {pid} ...but there are sub processes attached (I guess child processes) to java process. I wanna view all of them & kill whatever the process I like not the whole thing. I'm using Red hat 5 enterprise edition. and currently a weblogic application server is running on that.

View 2 Replies View Related

General :: Memory Optimization For Child Processes?

Sep 6, 2010

I work on Linux for ARM processor for cable modem. There is a tool that I have written (as the job demands) that sends/storms customized UDP packets using raw sockets. I form the packet from scratch so that we have the flexibility to play with different options. This tool is mainly for stress testing routers.I actually have multiple interfaces created. Each interface will obtain IP addresses using DHCP. This is done in order to make the modem behave as virtual customer premises equipment (vcpe).

When the system comes up, I start those processes that are asked to. Every process that I start will continuously send packets. So process 0 will send packets using interface 0 and so on. Each of these processes that send packets would allow configuration (change in UDP parameters and other options at run time). Thats the reason I decide to have separate processes. I start these processes using fork and excec from the provisioning processes of the modem. The problem now is that each process takes up a lot of memory. Starting just 3 such processes, causes the system to crash and reboot.

I have tried the following:-

1-I have always assumed that pushing more code to the Shared Libraries will. when I tried moving many functions into shared library and keeping minimum code in the processes, it made no difference to my surprise.

2-I also removed all arrays and made them use the heap. However it made no difference. This maybe because the processes runs continuously and it makes no difference if it is stack or heap?

3-I suspect the process from I where I call the fork is huge and that is the reason for the processes that I make result being huge. I am not sure how else I could go about. say process A is huge -> I start process B by forking and excec. B inherits A's memory area. So now I do this -> A starts C which inturn starts B will also not help as C still inherits A?. I used vfork as an alternative which did not help either. I do wonder why.

View 1 Replies View Related

Server :: Finding Child Processes Spawned From Screen?

Aug 25, 2010

I have a situation where I have several screen (/usr/bin/screen) sessions running. 2 of the screen sessions (ps1 and ps2) run a script that launched SipP with specific parameters. 1 script starts SipP and has it make 50 calls where the other makes only 20 calls. However The script is configured where we can change how many calls it makes if needed.

So the problem is, due to issues with SipP, we must restart everything every 12 hours (at maximum). So I am trying to work out scripts to stop the SipP processes cleanly. In order to do so I need to figure out which SipP process is spawned by which screen. i.e. which sipp was started by screen session ps1, and which one was started by screen session ps2.

Now I can do ps -ef | grep <number of calls configured> to find out but then I would have to change my stop script every time we reconfigure how many calls are made, and have a separate stop script for each screen session. I would much rather be able to send the screen name as a parameter to the stop script and have it work no matter how many calls SipP is configured to make.Also your standard kill -1 <PID> does not shutdown SipP cleanly. So working out those details is a bit more tricky. Anyone know how I can determine what processes are spawned from a specific screen session?

View 2 Replies View Related

Software :: Protect Environment Variables To Be Changed By Child Processes?

Jul 20, 2010

Im wondering if there is a simple way to protect environment variables to be changed by child processes?

View 1 Replies View Related

General :: Child Processes Of A Parent Process Occupying Socket Memory?

Jul 22, 2010

I am facing an issue where the process starts hanging. When I closely look at the logs I come to know that some of the child processes that are forked by the parent process are not finished.

1) Is it possible that the child processes that are not finished occupy the socket memory of the parent process and ultimately a point is reached where no socket memory is available to fork new child processes.

2) What is the standard limit of socket memory in linux?

3) What is the fate of such child processes (as I have mentioned above)?

4) How to debug such cases so that the exact problematic area is identified?

View 2 Replies View Related

Programming :: Find Number Of Threads In The Process In C Language?

Dec 23, 2009

I need to find how many threads are alive with respect to the current process for my further processing. Is there any means to trace this number ?[URL]I referred the above link. But sys/pstat.h is not in my system. Don't know which library gives this header.

View 14 Replies View Related

Programming :: Under Which Circumstances A Child Process Creates Another Child Process Using Fork

Dec 7, 2009

Consider the following code:

Code:

int main()
{
int i=0;
pid_t pid;
for(i=0;i<2;i++)

[code]....

I get the following output:

Parent: chid_pid=4356 i=0 parent's pid=4355
This is child 4356 i=0
This is child 4357 i=1

[code]....

I can observe instead of two children(as I expect) processes there are three. This is because child process 4356 creates its own child. Why all the messages of the type "This is child X i=Y" are concentrated one under another? How exactly fork works? Is affected by the fact that I have a dual-core processor?

View 3 Replies View Related

Programming :: Synchronize 2 Posix Threads ?

Mar 15, 2011

I have 2 threads and both of them are deleting memory at the end nedded by both.

My problem is that maybe it can happen that a thread start and finish before the other one starts and so it deletes the memory nedded by the other thread. How can I synchronize them so that this can't happend.

As a design my threads look like this:

Code:

The other thread looks the same, but this isn't unoff to stop thread1 to finish before thread2 starts.

View 4 Replies View Related

Ubuntu :: Ssh Banner With The Number Of Currently Running Processes?

May 18, 2010

I would like to do the following: Create a banner for any user logging in through ssh which warns him/her about the number of processors being used already by other users (or conversely the number of free processors). For example, if a user logged in he would then see a message like: Warning! 7 out of 8 processors are in use.I already figured out how to do a banner and with ps -e -o pcpu I can get all processes' %CPU usage. I think I would like to count the number of processes which have more than 90% CPU usage and output this number ("7" in the example) in the banner

View 7 Replies View Related

General :: Optimum Number Of Processes For Process?

Oct 24, 2009

Optimum number of processes for procesor In Linux based os are there a optimum number of process for a processor that gives 'maximum performance' for system(or process range depend on cpu speed,cache etc...)? By 'maximum performance' I mean better performance?

View 5 Replies View Related

Programming :: Proper Implementation Of POSIX Threads

Apr 6, 2011

I've implemented a program URL... which reads digital IF data from a radio receiver through a named pipe, measures power levels, and sends the result to stdout. The program is interactive; there is a thread that reads from stdin to watch for commands, a thread that constantly either reads data from the named pipe or throws data away, and an array of processing threads. The program uses GTK+extra to plot the signals. The IF data stream bandwidth exists at the limits of today's technology (is very very fast).

Problem Statement:The program works fine with a few bugs. I've learned since I've made it that using global state variables to coordinate threads isn't a good way of doing it. I also only had knowledge of mutexes and polled the state variable instead of using other methods.My reimplementation will use the following:

- One "Stdin Command Monitoring" thread
- One "Get data from named pipe" thread
- One post-processor thread
- N Processing threads

All threads are alive during the life of main()There are N buffers. Data will come in from the named pipe, and the "Get data" thread will write the data to an "available" buffer. When the buffer is full it will be marked as "full". There will be N processing threads, one for each buffer. When a processing threads' buffer is full, it will process the buffer and save the result to a final buffer. At the end of a number of averages, the post-processor thread will perform a final process on the final buffer and send the results to stdout.

View 2 Replies View Related

Server :: Increase Number Of Url_rewriter Processes In Squid?

Feb 28, 2009

Code...

I don't know how to increase the number of url_rewriter processes.

View 2 Replies View Related

Programming :: Closing / Unlinking POSIX Message Queues?

Apr 15, 2011

I have a pthread waiting forever on a POSIX message queue and then call mq_close and mq_unlink on the POSIX message queue. I've found that the pthread never wakes up from it's call to mq_receive and remains blocked indefinitely. Is there a way to wakeup all pthreads blocked on a POSIX message queue after calling mq_close/mq_unlink? The goal is to include error handling during message queue deletion to avoid leaving any pthreads blocked forever.

View 2 Replies View Related

Programming :: Posix Message Queues - Communicate Between Two Threads?

Jan 3, 2011

I want to communicate between two threads, each belonging to a different process. Iam using message queues for this. I use mq_open()call. I created the queues with the same queue name starting with a '/'. But when I open the queue, the queue ID is different in both the process. What should I do so that both the process have the same queue ID?

View 1 Replies View Related

Programming :: Related To Pthreads And Timers In POSIX Standard

Feb 17, 2010

I have created two threads:
Thread 1 and thread 2

In the main thread, i have put up a timer which generates a signal periodically when it expires, which reults in execution going to signal catcher function.when this function is invoked, under certain condition it goes to thread 1 and under another condition it goes to thread 2. The problem lies here that when it goes to thread2,i have a loop to process but it doesnt come out of the loop and hence from thread2, even though timer has expired.

View 2 Replies View Related

General :: Print The Number Of Processes That Each User Is Currently Running In Unix?

Mar 6, 2011

I'm trying to get the end result to have the same format as this as well:

1 bin
2 daemon
67 erozner

[code]....

Where the numbers are the number of processes being run by the user (the name right next to it).if I input the command egrep myFile into the terminal, it should look for every line with the letter x in myFile, right?

View 5 Replies View Related

Server :: Controlling Memory/number Of Processes For LDAP Users?

Jun 29, 2009

I know of /etc/security/limits.conf and that can be used to limit all sorts of good things, but I haven't found anything that talks about using this when the users come from LDAP. Would I be able to do something like

@"Domain Users" soft nproc 25
@"Domain Users" hard nproc 40

where Domain Users is the group all users belong to in our system.

View 3 Replies View Related

Programming :: Program Hang Stuck There Signal Handling On POSIX Message Queue UNIX C Pr

Jun 14, 2011

In a single main() function,so need signal handling. Use Posix Message Queue IPC mechanism , can ignore the priority and other linked list message,to implement the scenario:

View 1 Replies View Related

General :: Command To Find Parent And Child Process?

Apr 21, 2011

I have a script that calls other scripts/commands which may or may not spawn other process. From my understanding, when I do a ps -ef, the highest numbered process ID is supposed to be the parent ID of all the other related child processes, is this correct? In most or all circumstances, I do a ps -ef | grep <processid> of my script and anything that spawns off that process IDs I assumed are the child processes of my script. If I want to terminate my script and all other child processes, then I kill the parent ID which is the highest numbered PID and this will subsequently kill all other child process IDs, is this correct?

Now, my question is whether there is any quick way of showing what are the child processes of a parent ID instead of what am currently doing now which is visually checking which one is the parent ID and "assuming" that the highest numbered PID is the parent ID of all the other processes. Below is a sample output of running ps -ef | grep exp | grep -v grep. I assume from the output below that the parent process/ID is PID 11322, is that correct?

Code:

oracle 11154 11153 0 21:20 ? 00:00:00 /bin/sh -c (. ~oracle/.profile; /bin/ksh /usr/local/oracle/scripts/expdp_o
oracle 11155 11154 0 21:20 ? 00:00:00 /bin/sh -c (. ~oracle/.profile; /bin/ksh /usr/local/oracle/scripts/expdp_o
oracle 11190 11155 0 21:20 ? 00:00:00 /bin/ksh /usr/local/oracle/scripts/expdp_schema.ksh dev01
oracle 11322 11190 0 21:20 ? 00:00:00 expdp

View 2 Replies View Related

General :: Difference Between Child THREAD And Child PROCESS?

Jul 30, 2009

I am troubleshooting something and I got this problem.

If I do "pstree -p"

It shows,

Code:

[code]....

However, it does NOT show up in "ps -elf"

Code:

ps -elf | grep soffi
0 S whho 7734 1 0 80 0 - 36435 - 11:14 pts/2 00:00:03 /usr/lib/openoffice/program/soffice.bin -splash-pipe=5
0 S whho 7833 7759 0 80 0 - 751 - 11:21 pts/3 00:00:00 grep soffi

I was wondering if 7735, 7736, 7737, 7743 were really processes. Then I checked /proc, I could cd to /proc/7735, /proc/7736, etc, but I could not ls them out. I looked at the man page of "pstree", it says,

Code:

Child threads of a process are found under the parent process and are shown with the process name in curly braces, e.g.

icecast2---13*[{icecast2}]

So, what does all this mean? Does it mean that 7735, 7736, 7737, 7743 are just threads but not processes? If so, why could I cd to /proc/<id> but not see them in "ps -elf".

View 10 Replies View Related

Programming :: Can't Run Second Child In C (Fork)

Apr 10, 2011

Now,I created one parent and two children. I must create some value as random in child1 and child1 has to send these values to child2.Child2 must read them.. now,I cant create some random values and i can send them.But child2 doesnt work. I have two functions. One them is writing, another one is reading. Child2 uses reading function,but it doesnt work (child2 cant call it, because writing function in endless loop) What i must do? I used wait,usleep... No way.. I attached my file and also there is code..

PHP Code: #include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <stdarg.h>
#include <sys/types.h>
[Code].....

View 2 Replies View Related

Programming :: SetUID On Different PID Or Child Process

Aug 18, 2010

I have a root process (on linux) that forks a child and the child process then drops privileges by doing a setuid() to a normal user. After the child setuid()'s, it is of course impossible for it to gain root again by itself. But since the main process is still running as root, i was wondering if there was a simple/smart way of getting the root-master-process to elevate the child back to root (or maybe just to another non-privi uid). Is there some way to do a setuid() on another pid? or maybe something can be done through /proc/<pid>/? Killing the child is not an option (because its what it does today and im trying to find a smarter way). (The program is apache2's mpm-itk worker and the "child" is the actual apache2 process serving a page.)

View 11 Replies View Related







Copyrights 2005-15 www.BigResource.com, All rights reserved