This is a pretty basic question, but I can't get my head around
it. I'm learning Linux and one of the questions i've been given
is; *The word sentimentalment includes the same three characters
(e.g. "ent") which appear three times. The word "blayblapblam"
also contains the same three characters repeated three time
(e.g. "bla"). How many words can you find which contain any
three characters repeated three times, like the examples
"sentimentalment" and "blayblapblam", but which also begin with
lower case "d". Use /usr/share/dict/words as your list of
possible words and grep to find the answer. The "d" is not one
of the characters considered when detecting the three-character
strings.* So far, I can return instances where the same three
letters appear twice; grep -E '^d(...).*\1'
/usr/share/dict/words > output Which to me reads, look for a
word beginning with 'd', then combination of three letters, 0 or
more characters before the same group (1) appearing again. I've
tried the following; grep -E '^d(...).*\1.*\1'