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I`m trying to delete old files from directory and leave only 3 newest files.

cd /home/user1/test

while [ `ls -lAR | grep ^- | wc -l` < 3 ] ; do

    rm `ls -t1 /home/user/test | tail -1`
    echo " - - - "

done

something is wrong with conditional statement, can someone help me correct it?

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7 Answers 7

If you want to loop over files, never use ls*. tl;dr There are lots of situations where you'd end up deleting the wrong file, or even all files.

That said, unfortunately this is a tricky thing to do right in Bash. There's a working answer over at a duplicate question my even older find_date_sorted which you can use with small modifications:

counter=0
while IFS= read -r -d '' -u 9
do
    let ++counter
    if [[ counter -gt 3 ]]
    then
        path="${REPLY#* }" # Remove the modification time
        echo -e "$path" # Test
        # rm -v -- "$path" # Uncomment when you're sure it works
    fi
done 9< <(find . -mindepth 1 -type f -printf '%TY-%Tm-%TdT%TH:%TM:%TS %p\0' | sort -rz) # Find and sort by date, newest first

* No offense guys - I also used ls before. But it really isn't safe.

Edit: New find_date_sorted with unit tests.

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I second the part about not parsing ls. Also the script is neat but I think it could be done in a one liner, let me check ... –  rahmu Apr 5 '12 at 12:10
    
Well, you can always compact Bash code into a one-liner, but the issue is whether it'll be readable :) –  l0b0 Apr 5 '12 at 12:59
1  
If I may mercilessly steal an idea from @Peter.O, try ((++counter>3)) as your test. It's nicely succinct. As for oneliners: If brevity is a concern wrap the code in a function, then don't worry about it. –  Sorpigal Apr 5 '12 at 13:38
    
@Sorpigal Neat shortcut –  l0b0 Apr 5 '12 at 13:39

By far the easiest method is to use zsh and its glob qualifiers: Om to sort by decreasing age (i.e. oldest first) and [1,3] to retain only the first three matches.

rm *(Om[1,3])

See also How do I filter a glob in zsh for more examples.

And do heed l0b0's advice: your code will break horribly if you have file names that contain shell special characters.

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Woa woa hold the train, is this really a complete solution in 1 line? –  ioSamurai May 15 '12 at 16:34
    
@Ryan That's zsh for you. –  Gilles May 15 '12 at 18:28

You can use the following function to get the newest file in a directory:

newest_in() 
{ 
    local newest=$1

    for f;do [[ $f -nt $newest ]] && newest="$f"; done;

    printf '%s\n' "$newest"
}

Give it a different set of files by exculding the newest file after each iteration.

Tip: If you hold the initial set of files in an array called "${files[@]}", then save the index of the newest file found, and unset 'files[index]' before the next iteration.

Usage: newest_in [set of files/directories]

Sample output:

[rany$] newest_in ./*
foo.txt
[rany$]
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First, the -R option is for recursion, which is probably not what you want - that will search in all subdirectories as well. Second, the < operator (when not being seen as redirection) is for string comparison. You probably want -lt. Try:

while [ `ls -1A | grep ^- | wc -l` -lt 3 ]

But I would use find here:

while [ `find . -maxdepth 1 -type f -print | wc -l` -lt 3 ]
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Both will fail if one or more of the file names contain a '$\n'. –  Rany Albeg Wein Apr 28 '13 at 8:15

I know it's a sin to parse ls, but what about this:

find . -type f -maxdepth 1 | xargs ls -ltr | sed '1,3d' | awk '{print $9}' | xargs rm

A quick test with 5 empty files:

$ >1
$ >2
$ >3
$ >4
$ >5
$ find . -type f -maxdepth 1 | xargs ls -lt | sed '1,3d' | awk '{print $9}' | xargs rm
$ ls -1
3
4
5
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This one will fail for two reasons - Parsing ls output and using find and xargs together in the wrong way. If you combine find and xargs I recommend you to use finds -print0 and accordingly xargss -O options. Read about Using Find for more information about the subject. You might also want to take a look and read about why Parsing ls is very bad. –  Rany Albeg Wein Apr 28 '13 at 8:32

This one-liner does it all I think:

ls -t1 /home/user/test | tail -n +4 | xargs -I{} rm -- "{}"
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ls is a tool for interactively looking at file information. Its output is formatted for humans and will cause bugs in scripts. Use globs or find instead. Understand why: mywiki.wooledge.org/ParsingLs –  Rany Albeg Wein Apr 28 '13 at 8:34

Here's one solution:

rm /appserver/webapplogs/$(ls -t1 /appserver/webapplogs/|tail -1)
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@bakbak ls is a tool for interactively looking at file information. Its output is formatted for humans and will cause bugs in scripts. Look here to understand why. Specificaly speaking about your answer - this one will break if one or more of the files contain a $'\n' character. Also, the Command Substitution ( i.e. $(...) ) lacks double-quotes which brings up another important subject - Word Splitting! –  Rany Albeg Wein Apr 28 '13 at 8:23

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