GDB pid changes when connected automatically and quit - c

Question

I am trying to attach an existing process, run some commands and print the required information. However, when I do it, I see that the PID of the process is changed (with killed) command being displayed.
Code
1 #include <iostream>
2 #include <unistd.h>
3 using namespace std;
4
5
6 int main()
7 {
8 do
9 {
10 static int s = 100;
11 s = s+1;
12 sleep (3);
13 } while(1);
14 return 0;
15 }
16
GDB commands
> cat /tmp/command.txt
set pagination off
set logging file /home/testgrp/gdb.txt
set logging on
b sample.cc:11
commands 1
p s
end
run 1
quit
Output
root#198.18.81.198:/desktop/user1/workspace# ps -eaf | grep out
root 16724 8877 0 08:25 pts/1 00:00:00 grep --color=auto out
root#198.18.81.198:/desktop/user1/workspace# cat /home/testgrp/gdb.txt
cat: /home/testgrp/gdb.txt: No such file or directory
root#198.18.81.198:/desktop/user1/workspace# ./a.out &
[1] 16762
root#198.18.81.198:/desktop/user1/workspace# gdb --batch-silent -x=/tmp/command.txt -p 16762
[1]+ Killed ./a.out
root#198.18.81.198:/desktop/user1/workspace# ps -eaf | grep out
root 16805 1 0 08:25 pts/1 00:00:00 /desktop/user1/workspace/a.out 1
root 16823 8877 0 08:25 pts/1 00:00:00 grep --color=auto out
root#198.18.81.198:/desktop/user1/workspace# cat /home/testgrp/gdb.txt
Breakpoint 1 at 0x400711: file sample.cc, line 11.
$1 = 100
A debugging session is active.
Inferior 1 [process 16805] will be detached.
Quit anyway? (y or n) [answered Y; input not from terminal]
Question
How do I get the required information without changing the PID of the process?
More importantly, why does the pid change and previous PID is killed
Appendix
GDB version
GNU gdb (Ubuntu 7.7.1-0ubuntu5~14.04.2aka8.0.1) 7.7.1
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".

Answer 1

in the last two lines of your gdb scripts
run 1
quit
"run 1" will restart the program it is debugging with argument "1". by default, it should ask you to confirm restart or not.But you have an argument "--batch-silent" when you starting gdb. so your process restart without message.
delete "--batch-silent" and last 2 lines of your gdb script then you can break and debug.
"b sample.cc:11" will stop in system function sleep, you can change it to other line if you feel confuse . (I recommend you to read some simpler demos before using gdb,so many cmd will let beginner feel confuse)