How can I determine the IP address from a bash script?

Question

How do I get the IPaddress of the current machine from Bash in a cross platform compatible way? I need to get the IP address the same way for Windows Linux and Mac OS.

I am currently using docker-compose to create a local version of my full deployment, however I can't access it using localhost or 127.0.0.1, I have to refer to the current machines IP address, for example curl 192.168.0.23:80

Currently I make the user set the IP address manually:

# Return true if we pass in an IPv4 pattern.
not_ip() {
  rx='([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])'

  if [[ $1 =~ ^$rx\.$rx\.$rx\.$rx$ ]]; then
    return 1
  else
    return 0
  fi
}

# Ensure lower case
OPTION=$(echo $1 | tr [:upper:] [:lower:])

case "$OPTION" in
"test")
    LOCAL_IP=${LOCAL_IP:-$2}

    if not_ip "$LOCAL_IP" ; then
      echo The test command couldn\'t resolve your computers Network IP. $LOCAL_IP
      echo
      help_comment
      exit 1
    fi
    python -m webbrowser "http://${LOCAL_IP}:80/" &
    ;;
esac

However I would love to be able to get this without having to have the user set any environment variables, especially when dealing with Windows machines.

Any ideas?

Which is your network interface from which you want to get the IP address ? — mohit, Nov 02 '18 at 09:13
Possible duplicate of [Linux bash script to extract IP address](https://stackoverflow.com/q/21336126/608639) — jww, Nov 02 '18 at 18:04

score 1 · Answer 1 · answered Nov 02 '18 at 09:19

1

You need to detect host before use of the following because of OS specific commands

Windows (Cygwin command line )

LOCAL_IP=${LOCAL_IP:-`ipconfig.exe | grep -im1 'IPv4 Address' | cut -d ':' -f2`}

MacOS

LOCAL_IP=${LOCAL_IP:-`ipconfig getifaddr en0`} #en0 for host and en1 for wireless

Linux

LOCAL_IP=${LOCAL_IP:-`ifconfig | sed -En 's/127.0.0.1//;s/.*inet (addr:)?(([0-9]*\.){3}[0-9]*).*/\2/p'`}

answered Nov 02 '18 at 09:19

ntshetty

1,293
9
20

I like this approach, the only downside is that docker itself creates quite a few virtual devices with their own IPv4 and IPv6 addresses. Unfortunately I will get back multiple address matches on every platform. From experience the MacOS answer will probably work consistently, as long as I know which interface they are actually using. – Andre Lewis Nov 13 '18 at 22:27

How can I determine the IP address from a bash script?

1 Answers1