mid file deletion

["John T. Williams" <jtwilliams@vt.edu>]

What is the best way to remove data from the middle of a file. Here is the
Scenario: I have a file that is 20MB in size, about ¼ th way through it is a
1 line I want to remove. I can use lseek to bring me to the beginning of the
section I want to remove, and then lseek again to bring me to the end of
that section. The only thing I can think to do is load everything from the
file after the point I want to delete into memory, remove the part I don't
want from what is stored in memory (or simply don't load it), truncate the
file at the point where the part I wanted to delete began, and re-write the
rest of the file. The alternative (since 20MB is rather big for loading into
memory on a multi-User multi-Media machine) is to load the bits I want to
keep into a temporary file, rather into memory. However, I was thinking that
for removing 20bytes of information, reading and writing 15MB to 30MB is a
lot of work. Is there a better way?




To give this more of a real world perspective. I'm downloading e-mails into
a mbox file and I'm trying to figure out how to delete 1 email from a mbox
file that could potentially store 1,000's of e-mails an any given time.







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