How do I use sed to change my configuration files, with flexible keys and values?

I want to search a configuration file for this expression: "central.database". I then want to change the setting associated with "central.database" to "SQLTEST".

The layout of the config file would look like this initially:

central.database = SQLFIRSTTEST

This is what i want it to look like after the sed replacement:

central.database = SQLTEST

I am doing this in a bash script, any suggestions, recommendations or alternative solutions are welcome!

(Actually both central.database and SQLTEST come from bash variables here.)

My current code (third attempt):

sshRetValue=$(ssh -p "35903" -i $HOME/sshids/idrsa-1.old ${1} <<EOF
        sed -i "s/^\($CENTRAL_DB_NAME\s*=\s*\).*\$/\1$CENTRAL_DB_VALUE/" /home/testing.txt;
        echo $?
EOF
)

Error message:

Pseudo-terminal will not be allocated because stdin is not a terminal.
sed: -e expression #1, char 58: unknown option to `s'
-bash: line 3: EOF: command not found

Solution

Here's an example expression:

sed -i 's/^\(central\.database\s*=\s*\).*$/\1SQLTEST/' file.cfg

If you want to match stuff with / in it, you can use another delimiter:

sed -i 's#^\(cent/ral\.data/base\s*=\s*\).*$#\1SQL/TEST#' file.cfg

Or with variable expansion:

VAL="SQLTEST"
sed -i "s/^\(central\.database\s*=\s*\).*\$/\1$VAL/" file.cfg

In your example:

sshRetValue=`sed -i "s/^\(\1$CENTRAL_DB_NAME\s*=\s*\).*\$/\1$CENTRAL_DB_VALUE/" /home/testing.txt`;

There's a \1 before $CENTRAL_DB_NAME that's invalid. Also, sed doesn't print it's return value. This is the preferred way to check return values:

sed -i "s/^\($CENTRAL_DB_NAME\s*=\s*\).*\$/\1$CENTRAL_DB_VALUE/" /home/testing.txt;
sed_return_value=$?

And ultimately piping to ssh (not tested):

sed_return_value=$(ssh server <<EOF
    sed -i "s/^\($CENTRAL_DB_NAME\s*=\s*\).*\$/\1$CENTRAL_DB_VALUE/" /home/testing.txt;
    echo $?
EOF
)

The -i is for replacing data in the input file. Otherwise sed writes to stdout.

Regular expressions are a field of their own. It would be impossible to explain them in depth in a stackoverflow answer, unless there is some specific function that's eluding you.