tr -s '\n'
@end example
+@item
+Find doubled occurrences of words in a document.
+For example, people often write ``the the'' with the duplicated words
+separated by a newline. The bourne shell script below works first
+by converting each sequence of punctuation and blank characters to a
+single newline. That puts each ``word'' on a line by itself.
+Next it maps all uppercase characters to lower case, and finally it
+runs @code{uniq} with the @samp{-d} option to print out only the words
+that were adjacent duplicates.
+
+@example
+#!/bin/sh
+cat "$@@" \
+ | tr -s '[:punct:][:blank:]' '\n' \
+ | tr '[:upper:]' '[:lower:]' \
+ | uniq -d
+@end example
+
@end itemize