Scan Text Files for Control Characters

Posted On Tue, 16 Apr 2013

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A large part of programming in Batch is taken up with processing text files. By “text file”, I mean a plain text file with Windows line endings. And “plain text” means no nasty control characters such as Control-Z or the infamous Null Character.

For example, the former is used by copy /a and type as the end-of-file marker, while set and echo interpret the latter as the end of input.

So it’s always a good idea to scan any text files of unknown origin for these troublesome characters before doing anything else. Which is why I wrote the ctrlscan.cmd program described below…

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Generate Any Control Character

ASCII has 33 control characters. Many of them are defunct or are used for purposes for which they were not originally intended. Most of them are unprintable and some can cause problems if not filtered out of input. All the same, a handful of these characters have proven to be indispensible when it comes to performing certain tasks in Batch.

In this post, I’ll show you commonly-used techniques for generating specific control characters, as well as two lesser-known methods for storing almost any control character in a variable. But finding uses for them is an entirely different matter. One which will be covered in an upcoming post.

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