This shows an example of low level operating system programming that I use for instructional purposes.

There are two options:

• Output the last N lines of a file.
• Continuously output the content of a file that is growing.

1. Position to the end of the file (without reading anything)
2. Start reading backwards, counting newline characters
3. When enough lines have been read, output the lines

The key is not reading all the contents of the file, which yields a large performance gain which increases as the file size grows.

1. Read and output the contents of the file until the end is reached
2. Sleep for a while
3. Reset the end-of-file indication so that Step 1 can resume