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Wondering how would one go about writing a script that:

Counts the number of files in a directory.

If that number is greater than a specified number N, delete the oldest file in the directory.

For bonus feelings of good will: Only included .zip files in the count/delete.

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This feels a little like we may be doing school or real work for @Ryan. Perhaps you can demonstrate what you have come up with so far. –  uther May 14 '12 at 20:53
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It's not that I don't want to help, otherwise I wouldn't spend time here. What you are asking for is fairly trivial. It would go a long way to see you make an effort to write a script first and ask for critique/improvements instead of asking someone to write the script for you from scratch. I want you to learn something. –  uther May 14 '12 at 20:58
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man find, man wc, man ls –  Nils May 14 '12 at 21:00
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Why all the down-votes? BTW, possibly relevant reading. –  jw013 May 14 '12 at 21:28
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When you mouse over the downvote button it says: "This question does not show any research effort". If that doesn't apply here, when does it apply? –  Mikel May 14 '12 at 22:52
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2 Answers 2

N=50
[[ $( ls | wc -l ) -gt $N ]] && ls -tr | tail -n1 | xargs echo rm

Barely tested, but I think this comes close. If you are happy with the text output, you can remove the echo to set it live.

  • ls list files
  • wc count them
  • [[ ... -gt ... ]] if
  • && then
  • ls -tr list files in reverse age
  • tail -n1 show only last line
  • xargs echo rm append every argument found to echo rm
  • echo rm give you the opportunity to check if the result is really what you want
  • rm remove file
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This will break on filenames containing newlines. –  Chris Down May 14 '12 at 21:46
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This will break on filenames containing any kind of whitespace or \'". –  Gilles May 14 '12 at 23:11
    
Schoolbook assignments don't have newlines and quotes in filenames. ;o) –  jippie May 15 '12 at 6:28
    
@jippie this is for my minecraft server backups :) –  ioSamurai May 15 '12 at 15:44
    
Same for minecraft server backups ;o) (just guessing) –  jippie May 15 '12 at 19:07
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For example, to only perform the actions if there are more than 50 files in the folder:

shopt -s dotglob nullglob
for file in *; do
    [[ -f $file ]] && files+=( "$file" )
done
if (( ${#files[@]} > 50 )); then
    IFS= read -r -d $'\0' line < <(find . -maxdepth 1 -type f -printf '%T@ %p\0' 2>/dev/null | sort -z -n)
    rm "${line#* }"
fi
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