How to get bash variables from txt file?

Question

linux

I have a text file which contains 3 lines of text.

db
db_pass
db_pass

And there is a bash script that performs actions with these lines.

sudo mysqldump -u$username -p$password $database > $database.sql

Now I have to manually enter variables, it's not convenient.
Is there any way to get them out of the file?

Answer 1

You write variables to a file, as in a normal sh script - VAR1=foo, VAR2=bar, etc., and at the beginning of your script, say "source /path/to/varsfile", and all variables are pulled from there.

Answer 2

getlineno()
{
    sed -n "$2{p;q}" "$1"
}

username=`getlineno datafile.txt 2`
password=`getlineno datafile.txt 3`
database=`getlineno datafile.txt 1`

sudo mysqldump -u$username -p$password $database > $database.sql

unset password username database