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Want to remove all lines but not latest 50 lines from a file

 
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Top Forums UNIX for Dummies Questions & Answers Want to remove all lines but not latest 50 lines from a file
# 29  
Old 10-29-2013
Hi.

As alister said.

This behavior has been discussed in the forum, for example, I mentioned sponge / absorb for pipelines and re-writing-in-place in post #8 of https://www.unix.com/shell-programming-and-scripting/221749-run-command-without-over-writing.html -- that approach either keeps data in memory (say a perl array), or writes it to a scratch file first, both of which can preserve the inode if that is important. The sponge approach looks like the tee solution, but the internal logic differs by sponge collecting all the data until the end, then writing to the file argument, whereas tee streams the data to the file(s) as it comes in.

We cannot use the scratch file approach here because there is no additional disk space, so suggestions like the shell and dd above seemed appropriate. Both were validated on a file of 14M lines (~ 1 GB) with 50,000 lines being kept.

Best wishes ... cheers, drl
Last edited by drl; 10-30-2013 at 11:53 AM.. Reason: Minor typo.
 
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