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Accepted
icelizard
Asked: 2010-05-22 01:15:01 +0800 CST

Bash edit file and keep last 500 lines

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I am looking to create a cron job that opens a directory loops through all the logs i have created and deletes all lines but keep the last 500 for example.

I was thinking of something along the lines of

tail -n 500 filename > filename

Would this work?

I also not sure how to loop through a directory in bash

Thanks in advance.

logging bash tail

2 Answers

  1. Have you heard about logrotate? I think it's not good to erase logs.

    • 5
  2. Best Answer
    for file in *; do tail -n 500 filename > filename2 && mv filename2 filename ; done

    Writing to the file you're reading is not a good idea. My solution is also not good as you may lost log between tail and mv command.
    But anyway 

    for file in *;

    is a way to loop over files of a directory.

    But why don't you use logrotate ??

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