Parsing a config file in bash

Question

Here's my config file (dansguardian-config):

banned-phrase duck

banned-site allaboutbirds.org

I want to write a bash script that will read this config file and create some other files for me. Here's what I have so far, it's mostly pseudo-code:

while read line
do
    # if line starts with "banned-phrase"
        # add rest of line to file bannedphraselist
    # fi

    # if line starts with "banned-site"
        # add rest of line to file bannedsitelist
    # fi
done < dansguardian-config

I'm not sure if I need to use grep, sed, awk, or what.

Hope that makes sense. I just really hate DansGuardian lists.

Answer 1

With awk:

$ cat config
banned-phrase duck frog bird
banned-phrase horse
banned-site allaboutbirds.org duckduckgoose.net
banned-site froggingbirds.gov

$ awk '$1=="banned-phrase"{for(i=2;i<=NF;i++)print $i >"bannedphraselist"}
       $1=="banned-site"{for(i=2;i<=NF;i++)print $i >"bannedsitelist"}' config

$ cat bannedphraselist 
duck
frog
bird
horse

$ cat bannedsitelist 
allaboutbirds.org
duckduckgoose.net
froggingbirds.gov

Explanation:

In awk by default each line is separated into fields by whitespace and each field is handled by $i where i is the i^th field i.e. the first field on each line is $1, the second field on each line is $2 upto $NF where NF is the variable that contains the number of fields on the given line.

So the script is simple:

• Check the first field against our required strings $1=="banned-phrase"

• If the first field matched then loop over all the other fields for(i=2;i<=NF;i++) and print each field print $i and redirect the output to the file >"bannedphraselist".

Answer 2

You could do

sed -n 's/^banned-phrase *//p' dansguardian-config > bannedphraselist
sed -n 's/^banned-site *//p' dansguardian-config > bannedsitelist

Although that means reading the file twice. I doubt that the possible performance loss matters though.