How to find the main process PID without `master` identification?

Question

How to find the main process PID without master identification?

In this case:

[root@4d62e42f3cde conf.d]# ps -ef | grep demosoft
root      1700     1  0 08:34 pts/0    00:00:00 grep --color=auto demosoft
root     26814     1  0 Apr12 ?        00:00:00 demosoft --config=/etc/demosoft/demosoft.conf
demosoft    26815 26814  0 Apr12 ?        00:01:33 demosoft --config=/etc/demosoft/demosoft.conf
demosoft    26816 26814  0 Apr12 ?        00:01:36 demosoft --config=/etc/demosoft/demosoft.conf
demosoft    26817 26814  0 Apr12 ?        00:01:35 demosoft --config=/etc/demosoft/demosoft.conf
demosoft    26818 26814  0 Apr12 ?        00:01:32 demosoft --config=/etc/demosoft/demosoft.conf
demosoft    26819 26814  0 Apr12 ?        00:01:30 demosoft --config=/etc/demosoft/demosoft.conf
demosoft    26820 26814  0 Apr12 ?        00:01:29 demosoft --config=/etc/demosoft/demosoft.conf
demosoft    26821 26814  0 Apr12 ?        00:01:29 demosoft --config=/etc/demosoft/demosoft.conf
demosoft    26822 26814  0 Apr12 ?        00:01:30 demosoft --config=/etc/demosoft/demosoft.conf
demosoft    26823 26814  0 Apr12 ?        00:01:44 demosoft --config=/etc/demosoft/demosoft.conf

I only know use command: ps -ef | grep demosoft | awk '{print $2}' ps -ef | grep demosoft | awk '{print $2}' ps -ef | grep demosoft | awk '{print $2}' get the PIDs:

1710
26814
26815
26816
26817
26818
26819
26820
26821
26822
26823

I want to send SIGHUP signal to main process. but how?

you know if it is a Nginx process, I can send SIGHUP signal by:

kill -HUP $(ps -ef | grep nginx | grep master | awk '{print $2}')

but demosoft do not have the master identification.

Answer 1

You could install then use the pstree(1) command after having read its documentation.

You could also use the top(1) , pgrep(1) and pkill(1) commands after having read their documentation.

You could use signal(7) (see also proc(5) and signal-safety(7) ) and several syscalls(2) in your C program (maybe also with nftw(3) ...) after having read more documentation and Advanced Linux Programming

On most Linux systems, you may access /proc/ - read carefully proc(5)

You probably want to read documentation related to systemd(1) and credentials(7) .

I also recommend reading the documentation of Nginx . Since it is open source software, you are allowed to download its source code then improve it.

You could even (but there is a cybersecurity risk in doing so) write some FastCGI thing to remotely kill(2) processes (or use killpg(2) ) thru a web interface, or use libonion to write some webservice doing so, or contribute (in spring or summer 2021) to the RefPerSys project to do so more cleverly