CODEWITHSUNDEEP
unixgrep
ldehart
ldehart

Reputation: 5

Learning GREP, command does not work as I've been reading

So I've been given an assignment and the question is:

What command would you enter to see 5-letter words that begin with 'd' (upper or lower-case), followed by a lower-case vowel, and ending in 's'?

grep '^[Dd][aeiouy]..[s]' /usr/share/dict/words

^[Dd] Means that the first letter is D or d. Perfect.

[aeiouy] Means that the next letter will be one of those. Perfect.

Two dots means that the next two characters can be anything that they want. Perfect.

And s because it ends in an s. Perfect.

But when I hit enter, I'm getting things like debasements and debases. Not only are my parameters for grep being ignored, but it is reaching for too many words already, and I can't figure out what I've done wrong.

Upvotes: 0

Views: 970

Answers (2)

Daniel Liberman
Daniel Liberman

Reputation: 3

I believe ^ and $ are string terminators, so unless the line contains ONLY the word you're looking for, you won't find it. It only works on the dictionary file but not in general files, if you try. You should use \b on both sides as they're word boundaries.

\b[Dd][aeiouy]..[s]\b

But, grep will not return you only these words. It will return you the whole line that matches the expression, for example:

~$ grep "\b[Dd][aeiouy]..[s]\b" test
aacd danis daniel danis Dunns daniedanilsanielfk

In this case, just use the parameter -o, to print only matching words, one each line.

~$ grep -o "\b[Dd][aeiouy]..[s]\b" test
danis
danis
Dunns

Upvotes: 0

Christopher Helck
Christopher Helck

Reputation: 1140

You need to anchor the end. Like this:

grep '^[Dd][aeiouy]..[s]$' /usr/share/dict/words

Otherwise you're matching all words that start with '[Dd][aeiouy]..s' which is why you get things like "dumpster"

Upvotes: 1

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