Find all words containing characters in UNIX

Question

Given a word W, I want to find all words containing the letters in W from /usr/dict/words. For example, \"bat\" should return \"bat\" and \"tab\" (but not \"table\").

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Answer 1

You want to find words containing only a given set of characters. A regex for that would be:

'^[letters_you_care_about]*$'

So, you could do:

grep "^[$W]*$" /usr/dict/words

The '^' matches the beginning of the line; '$' is for the end of the line. This means we must have an exact match, not just a partial match (e.g. "table").

'[' and ']' are used to define a group of possible characters allowed in one character space of the input file. We use this to find words in /usr/dict/word that only contain the characters in $W.

The '*' repeats the previous character (the '[...]' rule), which says to find a word of any length, where all the characters are in $W.