12-18-2018
Question about global environment variables & fork() exec()
Hello... And thanks in advance for any help anyone can offer me on my question! I've been doing a lot of reading to try and find my answer... But I haven't had any luck
What I'm trying to understand is where a child process inherits global environment variables from? I understand the exec() system call overwrites environment variable created by the fork()... But how does exec() cause global environment variables to be included with a newly created child process if all the environment variables are overwritten? My best guess is that global environment variables are somehow excluded from being overwritten... But I can't confirm this
Also... when does the fork() assign a PID to a child process? Before or after it copies itself into a new region of memory?
Thanks to everyone for any assistance!
Last edited by bodisha; 12-18-2018 at 04:21 PM..
10 More Discussions You Might Find Interesting
1. Programming
Hello!
I am working on a server where I should have 4 (resident)processes, one of them being "the father" of the others, so I do 3 forks. The problem that I have is that I do an accept (for sockets) in the "father" process and I want to transmit the job to one of the processes "child" with... (3 Replies)
Discussion started by: driki
3 Replies
2. UNIX for Dummies Questions & Answers
Hi!
Can someone explain me exactly this technique? Why a process (PARENT) creates a copy of itself with FORK (CHILD)? What's the reason of this behaviour? Sorry, but I cannot understand the logic behind it.
Thanks. (4 Replies)
Discussion started by: marshmallow
4 Replies
3. Solaris
Hi,
I need to find/implement an application that FTPs (puts) all new files in a certain directory to an external storage unit. This application should check for new files every 10 seconds (leaving the FTP connection open in between the 10 seconds).
The easiest way would be if there are... (2 Replies)
Discussion started by: KittyJ
2 Replies
4. Shell Programming and Scripting
I need to ssh to a remote server and run my script there. This is my script.
$ssh = "ssh username@host";
$cmd = "$ssh 'cd <my dir> && < sudo Run_exe>'";
my $pid = fork;
if ($pid == 0){
exec $cmd;
}
When I run this I get:
pccons_getchar: got r == 0 (1 Reply)
Discussion started by: looza
1 Replies
5. Solaris
Hi Guys,
My requirement is I have file called /opt/orahome/.profile in non global zone.
PATH=/usr/bin:/usr/ucb:/etc:/usr/sbin:/usr/local/bin:/usr/openwin/bin:.
export PATH
PS1="\${ORACLE_SID}:`hostname`:\$PWD$ "
export PS1
EDITOR=vi
export EDITOR
ENV=/opt/orahome/.kshrc
export ENV... (1 Reply)
Discussion started by: vijaysachin
1 Replies
6. Programming
Hello World!
I am writing code in C++ which have to launch another application X using exec().
I would like to set some limits on it using setrlimit etc...
My problem is that i don't know how to forbid using fork() and strlimit by application X.
How can i do it? (3 Replies)
Discussion started by: kzi
3 Replies
7. Programming
Hello everybody.I want to make clear that i am not going to ask from anybody to build my asignement but i have a big problem. I can't seem to find anywhere ONE good example on C about what i am trying to do:wall:.I think it is simple. All i ask is one example, even a link is fine.
So, i want to... (1 Reply)
Discussion started by: Cuervo
1 Replies
8. UNIX for Dummies Questions & Answers
What is is difference between 'fork with exec' and 'fork without exec'?
How both are related? (1 Reply)
Discussion started by: kkalyan
1 Replies
9. Shell Programming and Scripting
I have the following bash script lines in a file named test.sh.
#!/bin/bash
#
# Write Date to cron.log
#
echo "Begin SSI Load $(date +%d%b%y_%T)"
#
# Get the latest rates file for processing.
#
d=$(ls -tr /rms/data/ssi | grep -v "processed" | tail -n 1)
filename=$d
export filename... (3 Replies)
Discussion started by: ginowms
3 Replies
10. Shell Programming and Scripting
Hello.
During startup /etc/bash.bashrc.local generates some array
.....
source /.../.../system_common_general_array_env_var
.....
The file system_common_general_array_env_var contains :
LEAP_VERSION='42.3'
ARRAY_MAIN_REPO_LEAP=('zypper_local' 'openSUSE-Leap-'"$LEAP_VERSION"'-Non-Oss' ... (2 Replies)
Discussion started by: jcdole
2 Replies
ENV(3) Library Functions Manual ENV(3)
NAME
env - environment variables
SYNOPSIS
bind #e /env
/env/var1
/env/var2
...
DESCRIPTION
The env device serves a one-level directory containing files with arbitrary names and contents. The intention is that the file name is the
name of an environment variable (see rc(1)), and the content is the variable's current value.
When a fork(2) system call creates a new process, both the parent and the child continue to see exactly the same files in the env device:
changes made in either process can be noticed by the other. In contrast, an rfork system call with the RFENVG bit set (see fork(2)) causes
a split: initially both process groups see the same environment files, but any changes made in one process group cannot be noticed by the
other. An rfork with RFCENVG splits and then clears the environment.
SEE ALSO
rc(1), fork(2)
SOURCE
/sys/src/9/port/devenv.c
BUGS
A write starting at an offset after the current extent of a file yields an error instead of zero filling.
ENV(3)