sed удалить часть строки

$ echo link= foo test bar test baz | sed -re 's:^link=.*test\s*(.*):\1:'
baz

$ echo link= foo test bar test baz | perl -npe 's:^link=.*?test\s*(.*):\1:'
bar test baz

$ echo "link=this is url and test rest of string" | sed 's/\(^link=\)\(.*\)test\s*\(.*\)/\1\3/'
link=rest of string

$ echo "link=this is url and test rest of string" | sed 's/\(^link=\)\(.*\)\(test.*\)/\1\3/'
link=test rest of string

$ echo "link=this_is_url_and_test_rest_of_string" | sed 's/\(^link=\)\(.*\)\(test.*\)/\1\3/'
link=test_rest_of_string

% echo "link=this_is _url/and/test_rest_of_string" | sed -e '/link=/ s:=.*\(test_\):=\1:'
link=test_rest_of_string

$ echo "link=link=this_is _url/and/test_rest_of_string" | sed 's#\(^link=\)\(.*\)\(test.*\)#\1\3#'
link=test_rest_of_string