How to extract a marked part of file

In this example we will extract a part of file marked by __BEGIN__ and __END__ labels and save it into another file.

This is the original file:

The edit rules we add:

1. Find regular expression "(\A.*^[[:print:]]*__BEGIN__[[:print:]]*\r\n)(.*)(^[[:print:]]*__END__[[:print:]]*\r\n.*\z)":

By this regular expression we break a file into three parts: "Preceeding text", "Interesting part" and "The rest".

See also the Regular Expressions Syntax.

2. Select the current content of a scratch file (we will use it as a temporary buffer):
Edit rule to select the current content of a scratch file

3. Put the "Interesting part" into scratch file:

4. Now let's prepare the new file name where the file will be saved. First, obtain the current file name:
Edit rule to obtain the file name and path

5. Then compose the new file name using the current path name and extension:

6. Finally, save the scratch file with the new name that we have created:
Edit rule to save the scratch file

Now the the Edit Rules window contains six rules as shown on the first plot.

Click "Apply all rules" to execute all rules and examine the Data View:

You can see the "Interesting part" moved to the scratch file and saved.

You can download the example files here: the original file, edit rules and the output file.

Please note that Mass File Editor becomes quite slow when opening a large files. It took several minutes to run this ruleset over a 15 Mb file:
Text got selected in a large file and saved