Replacing Source in The Twenty-First Century

In Searching Source in The Twenty-First Century, I introduced the use of regular expressions for searching within a source member. Searching is great, but sometimes you need to replace what the system finds with something else. Here’s how to replace text when using regular expressions.

Let’s begin with a source member.

Notice that there are nine constants named Stat10 through Stat90. Let’s replace Stat with Status_. Obviously we can’t replace Stat with Status everywhere it’s found. That would be disastrous!

Instead, let’s use a regular expression to find the instances where Stat is followed by a digit.

I clicked on the “All” button so that LPEX shows me only the lines that contain the search string.

Now it’s time to replace, but what is the replacement string? If I replace the matched characters with Status_, the digit will be obliterated, and I don’t want that. What I want to do is to replace that digit with itself, and to do that, I use a capturing (or capture) group.

In the Find box, I enclose \d in parentheses to indicate that whatever matches this piece of the search string is to be saved in the first capturing group. In the Replace box, I use the expression $1 to indicate the place where LPEX is to use the first capturing group. This expression replaces Stat with Status_ and the digit that follows Stat with itself.

Using regular expressions to search and replace text is like a multitude of other things you’ve done. Once you do it a few times, you’ll wonder why you ever thought it was hard.

Ted Holt welcomes your comments and questions. Email him through the IT Jungle Contacts page.

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