Make awk print a specific segment of a single line

Question

I have a file called LogsDocker that contains

export DOCKER_TLS_VERIFY="1"
export DOCKER_HOST="tcp://192.168.99.100:2376"
export DOCKER_CERT_PATH="/root/.docker/machine/machines/Main-hola"
export DOCKER_MACHINE_NAME="Main-hola"
# Run this command to configure your shell: 
# eval $(docker-machine env Main-hola)

and i want to print only the ip

192.168.99.100

Just discovered Awk and with the command

 awk 'BEGIN { FS = "//"} ; { print $2}' LogsDocker

made it print (with a bunch of empty lines)

192.168.99.100:2376"

What would be the correct way to print ONLY the ip without empty lines

Answer 1

Could you please try following.

awk '/DOCKER_HOST/ && match($0,/[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/){print substr($0,RSTART,RLENGTH)}' Input_file

Explanation: Adding explanation for above code.

awk '                                                             ##Starting awk program from here.
/DOCKER_HOST/ && match($0,/[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/){      ##Checking condition if string DOCKER_HOST is found in line AND match is having a mentioned regex matched in it.
  print substr($0,RSTART,RLENGTH)                                 ##If above conditions are TRUE then printing substring whose starting index is RSTART and ending index is RLENGTH.
}
' Input_file                                                      ##Mentioning Input_file name here.

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2nd solution: Considering that your Input_file will always be same then try following.

awk -F'[/:]' '/DOCKER_HOST/{print $4}' Input_file

Explanation: Adding explanation for above code.

awk -F'[/:]' '      ##Starting awk program from here and setting field separator as /or colon here.
/DOCKER_HOST/{      ##Checking condition if a line has string DOCKER_HOST then do following.
  print $4          ##Printing 4th field of current line.
}
' Input_file        ##Mentioning Input_file name here.

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3rd solution: A sed solution.

sed -n '/DOCKER_HOST/s/.*\///;s/:.*//p'  Input_file

Explanation: Following is only for explanation purposes.

sed -n '          ##Starting sed program from here and making printing off for all lines until specifically mentioned.
/DOCKER_HOST/     ##Searching string DOCKER_HOST in lines if present then do following.
s/                ##s means perform substitution operation here.
.*\/              ##mentioning regex which covers everything till / in line, if matched this regex
//                ##Then substitute it with NULL here.
;                 ##semi colon denotes to segregate another substitute operation after this one.
s/                ##Doing substitution from here.
:.*               ##Match everything from : to till last of line.
//                ##Substitute above matched values with NULL in current line.
p                 ##p means only print this line.
'  Input_file     ##Mentioning Input_file name here.

Answer 2

Assuming given your existing code that the IP address is the only place you have // :

$ awk 'sub(/.*\/\//,""){sub(/:.*/,""); print}' file
192.168.99.100

or making other assumptions...:

$ awk -F'//|:' 'NF>2{print $3}' file
192.168.99.100

or:

$ awk -F'//|:' '/DOCKER_HOST=/{print $3}' file
192.168.99.100

or ....

It really just depends what else is in that file and how robust you want it to be.