How to remove duplicate words from a plain text file using linux command

Question

I have a plain text file with words, which are separated by comma, for example:

word1, word2, word3, word2, word4, word5, word 3, word6, word7, word3

i want to delete the duplicates and to become:

word1, word2, word3, word4, word5, word6, word7

Any Ideas? I think, egrep can help me, but i'm not sure, how to use it exactly....

Answer 1

Assuming that the words are one per line, and the file is already sorted:

uniq filename

If the file's not sorted:

sort filename | uniq

If they're not one per line, and you don't mind them being one per line:

tr -s [:space:] \\n < filename | sort | uniq

That doesn't remove punctuation, though, so maybe you want:

tr -s [:space:][:punct:] \\n < filename | sort | uniq

But that removes the hyphen from hyphenated words. "man tr" for more options.