sudo service nginx restart 
Redirecting to /bin/systemctl restart nginx.service
Job for nginx.service failed because the control process exited with error code. See "systemctl status nginx.service" and "journalctl -xe" for details.

systemctl status nginx.service               

● nginx.service - The nginx HTTP and reverse proxy server
   Loaded: loaded (/usr/lib/systemd/system/nginx.service; disabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Mon 2019-05-13 17:15:38 CST; 7min ago
  Process: 24060 ExecStart=/usr/sbin/nginx (code=exited, status=1/FAILURE)
  Process: 24056 ExecStartPre=/usr/sbin/nginx -t (code=exited, status=0/SUCCESS)
  Process: 24054 ExecStartPre=/usr/bin/rm -f /run/nginx.pid (code=exited, status=0/SUCCESS)

ps aux | grep nginx                                                                                                    
root     23885  0.0  0.0 125100  2164 ?        Ss   16:57   0:00 nginx: master process /usr/sbin/nginx
nginx    23886  0.0  0.0 125620  3636 ?        S    16:57   0:00 nginx: worker process
nginx    23887  0.0  0.0 125620  3636 ?        S    16:57   0:00 nginx: worker process
yak      24099  0.0  0.0 112708   976 pts/7    S+   17:26   0:00 grep --color=auto nginx

sudo /usr/sbin/nginx
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to [::]:80 failed (98: Address already in use)
nginx: [emerg] still could not bind()