Filters are fun to code and useful, such as the more<\/em> filter in Linux that pages text output. For this month’s Exercise, your task is to write a text reversing filter. This program is a bit more challenging than coding other types of filters. A common filter example is the Caesarian Cypher, which I wrote about<\/a> a dozen years ago. (It was the August 2013 Exercise post.) This filter takes text and rotates the letters 13 positions to encrypt. Re-running the encrypted text through the same filter decrypts, which makes it useful but not a completely foolproof encryption method.<\/p>\n Most filters I’ve written about in this blog are simple I\/O filters. But the task at hand is to reverse all input and generate output. For example, the following text is input:<\/p>\n The filter generates this output:<\/p>\n The rub here is that the input text must be stored so that it can be processed in reverse order. This hurdle is what elevates your task beyond just writing a simple I\/O filter.<\/p>\n No, you can’t cheat by having the filter output a “buffer full” message or something equally snarky. The filter must handle all input, whatever size, then regurgitate the input in reverse order for the output.<\/p>\n Click here<\/a> to view my solution.<\/p>\n","protected":false},"excerpt":{"rendered":" Write a filter to output text in reverse. Continue reading
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\nAs a review, a filter takes standard input, modifies it somehow, then generates standard output. This approach allows for text to be read directly from the terminal, input from a file, or redirected as output from another program. It’s this flexibility that makes filters so useful.<\/p>\nThis is a test<\/code><\/p>\ntset a si sihT<\/code><\/p>\n