The address of, say, 0xbfffffffff can hold its own, separate value in each and every individual process. That's really the point of having processes -- each one gets its own flat memory space, as if it was the only thing running on the computer, but it's actually quite secure and controlled.
This virtual memory space works by dividing real memory into 4096-byte chunks, and keeping a big table of which process gets what real memory at what virtual address. This table is checked in hardware by the processor itself, and configured by the kernel. If a process tries to access a memory location where no real pages have been assigned to it, you get the familiar error "segmentation fault".
What fork() does is it makes an exact copy of the process at the time of the fork(), but gives it its own independent memory space, then twiddles the value of 'pid' so it's different in the child. It uses some tricks like copy-on-write to avoid duplicating too much memory, but that's mostly safe to ignore.
These 2 Users Gave Thanks to Corona688 For This Post:
I don't follow what these are...
this is what my text says...
"When a process is started, a duplicate of that process is created. This new process is called the child and the process that created it is called the parent. The child process then replaces the copy for the code the parent... (1 Reply)
Hello.
I have a global function name func1() that I am sourcing in from script A. I call the function from script B. Is there a way to find out which script called func1() dynamically so that the func1() can report it in the event there are errors?
Thanks (2 Replies)
Hello,
How many child processes are actually created when running this code ?
#include <signal.h>
#include <stdio.h>
int main () {
int i ;
setpgrp () ;
for (i = 0; i < 10; i++) {
if (fork () == 0) {
if ( i & 1 ) setpgrp () ;
printf ("Child id: %2d, group: %2d\n", getpid(),... (0 Replies)
Hello,
How many child processes are actually created when running this code ?
#include <signal.h>
#include <stdio.h>
int main () {
int i ;
setpgrp () ;
for (i = 0; i < 10; i++) {
if (fork () == 0) {
if ( i & 1 ) setpgrp () ;
printf ("Child id: %2d, group: %2d\n",... (1 Reply)
Hello, I'm trying to implement a version of a bucketSort (kinda) server/client, but I'm having a VERY hard time on making the server behave correctly, when talking to the children, after it forks.
The server is kinda big (300+ lines), so I won't post it here, but here's what I'm doing.
1)create a... (8 Replies)
Hi
I am trying to see if there are some options in ps command or if there is a shell script which basically shows you all the processes spawned by a parent process , then all the processes of its child processes and so on down the hierarchy may be like a tree structure. It might be a generic... (6 Replies)
Consider this simple command line
bash -c 'echo $$ ; sleep 10000'This will print the newly created bash PID and sleep for a long time.
If I go to another terminal and do something like
ps -flax | grep leepI'll see something like
501 92418 91910 0 0:00.00 ttys000 0:00.00 bash -c echo $$... (5 Replies)
Hello,
I am trying to create a pipe that will direct stdout to in side of the pipe, and stdin to the out side of the pipe - I created two child processes to handle this. However, my pipe doesn't seem to be working correctly. Did I use execv() correctly? Command1 and command2 represent the two... (3 Replies)
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... (2 Replies)
I am trying to kill PIDs that are tied to a KSH "load_sqlplus" and I am using the below code
LIST_PID=`ps -ef | grep -i "load_sqlplus" | grep -v grep | awk '{print $2}'`
if ; then
echo "Processes killed" "PID : " $LIST_PID
kill -9 $LIST_PID
else
echo "Nothing to Kill"
fi... (4 Replies)
Discussion started by: venky338
4 Replies
LEARN ABOUT BSD
fork
FORK(2) System Calls Manual FORK(2)NAME
fork - create a new process
SYNOPSIS
pid = fork()
int pid;
DESCRIPTION
Fork causes creation of a new process. The new process (child process) is an exact copy of the calling process except for the following:
The child process has a unique process ID.
The child process has a different parent process ID (i.e., the process ID of the parent process).
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.
The child processes resource utilizations are set to 0; see setrlimit(2).
RETURN VALUE
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 one or more of the following are true:
[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.
SEE ALSO execve(2), wait(2)3rd Berkeley Distribution May 22, 1986 FORK(2)