How do prevent whitespace from appearing in these bash variables?

Question

I'm reading in values from an .ini file, and sometimes may get trailing or leading whitespace.

How do I amend this first line to prevent that?

db=$(sed -n 's/.*DB_USERNAME *= *\([^ ]*.*\)/\1/p' < config.ini);
echo -"$db"-

Result;

-myinivar -

I need;

-myinivar-

Answer 1

You don't need the .* inside the capturing group (or the semicolon at the end of line):

db="$(sed -n 's/.*DB_USERNAME *= *\([^ ]*\).*/\1/p' < config.ini)"

To elaborate:

1. .* matches anything at all
2. DB_USERNAME matches that literal string
3. * (a single space followed by an asterisk) matches any number of spaces
4. = matches that literal string
5. * (a single space followed by an asterisk) matches any number of spaces
6. \( starts the capturing group that is used for \1 later
   1. [^ ] matches anything which is not a space character
   2. * repeats that zero or more times
7. \) ends the capturing group
8. .* matches anything at all

Therefore, the result will be all the characters after DB_USERNAME = and any number of spaces, up to the next space or end of line, whichever comes first.

Answer 2

Use parameter expansion.

echo "=${db% }="

Answer 3

You can use echo to trim whitespace:

db='myinivar '
echo -"$(echo $db)"-
-myinivar-

Answer 4

Use crudini which handles these ini file edge cases transparently

db=$(crudini --get config.ini '' DB_USERNAME)

Answer 5

To get rid of more than one trailing space, use %% which removes the longest matching pattern from the end of the string

echo "=${db%% *}="