Question

I’m writing an application which will use a log file. What I want to do is when the application starts it will check to see if the log file is above a certain size and if it is it will delete ‘x’ amounts of lines from the top of the log file to shorten it up. What would be a good way of going about doing this? Would it be easier to write the most recent entries to the top of the file and then delete from the bottom when I do delete?

Answer 1

So you have a log file, let’s call it “log.log“

First, move log.log to log.log.bak. Open it for reading. Read line by line until you have read x number of lines. Open a new file, log.log, for writing. Continue reading lines from log.log.bak and for each line write it to log.log. When there are no more lines, close log.log and log.log.bak and then delete log.log.bak.

Some pseudo code:

x = number of lines to delete

move log.log to log.log.bak

open log.log.bak for reading
while i have read < x lines
    read a line and throw it away

open log.log for writing
while there are more lines in log.log.bak
    read a line from log.log.bak
    write the line to log.log

close log.log
close log.log.bak

delete log.log.bak