[GRASS5] 5.7 how to merge polygons with same attribute ?

[Moritz Lennert]

Hello,

How do I merge polygons with the same value for a given attribute in the
attribute table ?

For example: if I have a map of the world by countries, and for each country
an attribute "continent" in the database table with values such as "Europe",
"North America", etc, how could I create a map showing only the outlines of
the continents ?

Moritz