Removing content from a file

Operations such as copying, renaming, moving, or deleting files are directly provided by the filesystem library. However, when it comes to removing content from a file, you must perform explicit actions.

Regardless of whether you need to do this for text or binary files, you could implement the following pattern:

1. Create a temporary file.
2. Copy only the content that you want from the original file to the temporary file.
3. Delete the original file.
4. Rename/move the temporary file to the name/location of the original file.

In this recipe, we will learn how to implement this pattern for a text file.

Getting ready

For the purpose of this recipe, we will consider removing empty lines, or lines that start with a semicolon (;), from a text file. For this example, we will have an initial file, called sample.dat, that contains the names of Shakespeare’s plays, but also empty lines and lines that start with a semicolon...