Shell – How to get only the PID, without any extra information, of a process running on port 3000

linuxportprocessshell-script

I'm using CentOS 7. I want to get the PID (if one exists) of the process running on port 3000. I would like to get this PID for the purposes of saving it to a variable in a shell script. So far I have

[rails@server proddir]$ sudo ss -lptn 'sport = :3000'
State      Recv-Q Send-Q                           Local Address:Port                                          Peer Address:Port
Cannot open netlink socket: Protocol not supported
LISTEN     0      0                                            *:3000                                                     *:*                   users:(("ruby",pid=4861,fd=7),("ruby",pid=4857,fd=7),("ruby",pid=4855,fd=7),("ruby",pid=4851,fd=7),("ruby",pid=4843,fd=7))

but I can't figure out how to isolate the PID all by itself without all this extra information.

Best Answer

Another possible solution:

lsof -t -i :<port> -s <PROTO>:LISTEN

For example:

# lsof -i :22 -s TCP:LISTEN
COMMAND  PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
sshd    1392 root    3u  IPv4  19944      0t0  TCP *:ssh (LISTEN)
sshd    1392 root    4u  IPv6  19946      0t0  TCP *:ssh (LISTEN)
# lsof -t -i :22 -s TCP:LISTEN
1392

Related Solutions

Linux Process – Finding the PID of the Process Using a Specific Port

Your existing command doesn't work because Linux requires you to either be root or the owner of the process to get the information you desire.

On modern systems, ss is the appropriate tool to use to get this information:

$ sudo ss -lptn 'sport = :80'
State   Local Address:Port  Peer Address:Port              
LISTEN  127.0.0.1:80        *:*                users:(("nginx",pid=125004,fd=12))
LISTEN  ::1:80              :::*               users:(("nginx",pid=125004,fd=11))

You can also use the same invocation you're currently using, but you must first elevate with sudo:

$ sudo netstat -nlp | grep :80
tcp  0  0  0.0.0.0:80  0.0.0.0:*  LISTEN  125004/nginx

You can also use lsof:

$ sudo lsof -n -i :80 | grep LISTEN
nginx   125004 nginx    3u  IPv4   6645      0t0  TCP 0.0.0.0:80 (LISTEN)

Shell – How to get the PID of a sub process across to the parent process in a bash shell script

Since you tagged this as Linux: pgrep / pkill to the rescue:

PID_OF_SUB_PROCESS1=$( pgrep -P $PID_OF_PROCESS1 )
pkill -P $PID_OF_PROCESS1

Best Answer

Related Solutions

Linux Process – Finding the PID of the Process Using a Specific Port

Shell – How to get the PID of a sub process across to the parent process in a bash shell script

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