forking and killing parent processes Post: 86644

Sponsored Content

Top Forums UNIX for Dummies Questions & Answers forking and killing parent processes Post 86644 by davewilliams20 on Monday 17th of October 2005 05:40:47 AM

10-17-2005

Registered User

forking and killing parent processes

Hi everybody,

I'm having some problems wiriting a program in UNIX using the "fork" and "kill" system calls.

I have to create a C program P0, which creates 9 other processes
P1, P2, ..., P9, where P0 is the father of P1, P1 the father of P2, and so on.

All the processes contain an infinite loop.

When all the processes are created P9 executes the command "ps".
Then P9 kills P8, execute "ps", then kills P7, executes "ps", and so
on till only the process P0 and P9 remain.

I've created the 9 processes in the following way:

P0 does a fork. The child process executes p1 and the parent process enters and infinite loop.
p1 to p8 do the same thing.
p9 then executes ps.

Up to here there are no problems, ps is executed and everything seems to be working fine, the PID and PPID are correct, and all the processes are marked as running.

The problem I have is how to kill the parents of p9.

I use the kill function, but for this I need the PID of the processes to kill.
How can this be found?

To see at least if the kill process does what's it supposed to do, I use the getppid() system call to retrieve the PID of process p9's father and loop it back from there (not very elegant but should work in theory).

With this pid I then use the kill function with the SIGKILL signal and the pid of the process to be killed.

The problem here is that only p8 gets killed while the rest of the processes keep running!

Therefore the process p9 does something like this:

Code:

int main() {

	execute_ps()

	kill_parents()

}

void execute_ps() {

	pid = fork();

	if (fork != 0)
		wait();

	else
		execl("/bin/ps","",0)

}

void kill_parents() {

	parent = getppid();

	for (i=0; i<8; i++) {

		kill(parent, SIGKILL);
		parent--;
		execute_ps();

	}

	execute_ps();

}

Any help/suggestions are welcome!

Thanks a lot

David

davewilliams20

View Public Profile for davewilliams20

Find all posts by davewilliams20

10 More Discussions You Might Find Interesting

1. Programming

forking n number of processes in a loop and not 2^n

Hi, Am working on linux. while forking in a loop how to avoid the child process from forking..for example int n = 5; pid_t pid; pid_t ch_pid; /*exactly wanted to create n processes and not 2^n processes*/ for(i = 0; i < n;i++) { if(pid = fork()) { /* parent...

2. Shell Programming and Scripting

Killing parent shells from subshells (KSH)

Hi all, I have a shell script which calls other shell scripts, depending on the input. Within a.sh, I have a command which calls b.sh (ie. ksh b.sh) Normally, we use the exit function to terminate a shell. However, if I choose to call exit from b.sh, I will return to the parent shell who...

3. UNIX for Advanced & Expert Users

Monitoring Processes - Killing hung processes

Is there a way to monitor certain processes and if they hang too long to kill them, but certain scripts which are expected to take a long time to let them go? Thank you Richard

4. UNIX for Advanced & Expert Users

Forking a new process without parent dependance

hi, I want my program to fork a new process and then I want to kill the parent process. The parent program before dying will issue a SIGTERM to all its childs. Which eventually kills all Children. I cant handle the SIGTERM at the child level.:( What I was thinking of was the Parent...

5. UNIX for Advanced & Expert Users

Child Killing Parent

Hi all, I am writing a script which calls other third party scripts that perform numerous actions. I have no control over these scripts. My problem is, one of these scripts seems to execute and do what it is meant to do, but my calling / parent script always exits at that point. I need to...

6. Shell Programming and Scripting

Forking a bunch of processes and filling up the process table

I have a bash script that has been used for months here at work for doing an SSH into other machines both Linux and Solaris and running a script on the remote machine. Recently I have started to noticed that things are being left being on the maching doing the SSH. For example.... tivoli ...

7. Shell Programming and Scripting

Finding the age of a unix process, killing old processes, killing zombie processes

I had issues with processes locking up. This script checks for processes and kills them if they are older than a certain time. Its uses some functions you'll need to define or remove, like slog() which I use for logging, and is_running() which checks if this script is already running so you can...

8. Programming

Parent forking

My question is, how do you fork only the parent processes in unix? For example how would I use the fork function to fork the parent process more than once and leave the children processes alone. This way I do not have children of children. The way I have it set up now it the parent process forks 3...

9. Shell Programming and Scripting

forking a child process and kill its parent to show that child process has init() as its parent

Hi everyone i am very new to linux , working on bash shell. I am trying to solve the given problem 1. Create a process and then create children using fork 2. Check the Status of the application for successful running. 3. Kill all the process(threads) except parent and first child...

10. Solaris

Child killing parent process and how to set up SMF

Hello, A little background on what we are doing first. We are running several applications from a CLI, and not all of them are fully functional. They do on occasion core dump, not a problem. We are running a service that takes a screen scrape of those apps and displays them in a more user...

LEARN ABOUT MOJAVE

fork

FORK(2) 						      BSD System Calls Manual							   FORK(2)

NAME

     fork -- create a new process

SYNOPSIS

     #include <unistd.h>

     pid_t
     fork(void);

DESCRIPTION

     fork() causes creation of a new process.  The new process (child process) is an exact copy of the calling process (parent process) except for
     the following:

	   o   The child process has a unique process ID.

	   o   The child process has a different parent process ID (i.e., the process ID of the parent process).

	   o   The child process has its own copy of the parent's descriptors.	These descriptors reference the same underlying objects, so that,
	       for instance, file pointers in file objects are shared between the child and the parent, so that an lseek(2) on a descriptor in the
	       child process can affect a subsequent read or write by the parent.  This descriptor copying is also used by the shell to establish
	       standard input and output for newly created processes as well as to set up pipes.

	   o   The child processes resource utilizations are set to 0; see setrlimit(2).

RETURN VALUES

     Upon successful completion, fork() returns a value of 0 to the child process and returns the process ID of the child process to the parent
     process.  Otherwise, a value of -1 is returned to the parent process, no child process is created, and the global variable errno is set to
     indicate the error.

ERRORS

     fork() will fail and no child process will be created if:

     [EAGAIN]		The system-imposed limit on the total number of processes under execution would be exceeded.  This limit is configuration-
			dependent.

     [EAGAIN]		The system-imposed limit MAXUPRC (<sys/param.h>) on the total number of processes under execution by a single user would
			be exceeded.

     [ENOMEM]		There is insufficient swap space for the new process.

LEGACY SYNOPSIS

     #include <sys/types.h>
     #include <unistd.h>

     The include file <sys/types.h> is necessary.

SEE ALSO

     execve(2), sigaction(2), wait(2), compat(5)

HISTORY

     A fork() function call appeared in Version 6 AT&T UNIX.

CAVEATS

     There are limits to what you can do in the child process.	To be totally safe you should restrict yourself to only executing async-signal
     safe operations until such time as one of the exec functions is called.  All APIs, including global data symbols, in any framework or library
     should be assumed to be unsafe after a fork() unless explicitly documented to be safe or async-signal safe.  If you need to use these frame-
     works in the child process, you must exec.  In this situation it is reasonable to exec yourself.

4th Berkeley Distribution					   June 4, 1993 					 4th Berkeley Distribution

10 More Discussions You Might Find Interesting

1. Programming

forking n number of processes in a loop and not 2^n

Discussion started by: rvan

2. Shell Programming and Scripting

Killing parent shells from subshells (KSH)

Discussion started by: rockysfr

3. UNIX for Advanced & Expert Users

Monitoring Processes - Killing hung processes

Discussion started by: ukndoit

4. UNIX for Advanced & Expert Users

Forking a new process without parent dependance

Discussion started by: tyler_durden