Bash – Will ls Always List Files That rm Will Remove?

18.04bashhidden-fileslsrm

Something I feel I ought to know for sure: if I ls <something>, will rm <something> remove exactly the same files that ls displayed? Are there any circumstances where rm could remove files that ls did not show? (This is in the 18.04 bash)

Edit: thank you to everyone who answered. I think the full answer is a combination of all the answers, so I have accepted the most up-voted answer as "the answer".

Unexpected things I have learned along the way:

ls is not as straightforward as you might think in its handling of its arguments
In a simple un-fiddled-with installation of Ubuntu, .bashrc aliases ls
Don't name your files beginning with a dash as they can look like command arguments, and naming one -r is asking for it!

Best Answer

Well, both ls and rm operate on the arguments which are passed to them.

These arguments can be a simple file, so ls file.ext and rm file.ext operate on the same file and the outcome is clear (list the file / delete the file).

If instead argument is a directory, ls directory lists the content of the directory while rm directory won't work as is (i.e. rm without flags cannot remove directories, while if you do rm -r directory, it recursively deletes all files under directory and the directory itself).

But keep in mind that command line arguments can be subjected to shell expansion, so it's not always guaranteed that the same arguments are passed to both commands if they contain wildcards, variables, output from other commands, etc.

As an extreme example think ls $(rand).txt and rm $(rand).txt, the arguments are "the same" but the results are quite different!

Related Solutions

Ubuntu – List all files that do not have extensions

shopt -s extglob ## enables extended globbing
ls !(*.*) ## matches every file except those containing a dot

You will find that doing this will show you the contents of every directory in the working directory. If you don't want this, use:

ls -d !(*.*)

You can put shopt -s extglob in your ~/.bashrc to have it activated whenever you open a terminal. There is already a line in the default Ubuntu ~/.bashrc (line 29 for me on 13.04) that you can uncomment to enable this (and globstar).

See Greg's wiki for more information on the shell's various globbing options. Note that this is a property of the bash shell rather than the ls command, so you can use it with other commands.

Alternatively, you can use

ls --ignore='*.*'

ls -I '*.*'

...which is an internal ls option, but extglob can be applied to any arbitrary command & so is more useful in my opinion.

Ubuntu – how to remove files in a list of paths easily

What's your input? A file? A command? Either way, xargs should be helpful:

cat file | xargs rm

... will delete every path for every line in the file. If it's just a command that's outputting a path on each line, pipe it through xargs and it should work well.

Alternatively, use xargs --arg-file="file.txt" rm. This saves on pipe and unnecessary cat.

If you're looking to do more with each line, you could use a traditional bash while loop:

# uses echo for testing
# remove # before rm for actual deletion
while read -r path; do
    echo "deleting $path"
    # rm "$path"
done < file

If your list is the output of find, you have another couple of options, including a -delete option or using -exec rm {} \+. There are almost certainly a few dozen other viable routes to success. If you're doing automated deletion with find, just check the output before you delete. It won't forgive you your mistakes.

Spaces can be a problem with piping things into xargs. This might not be an issue for you and your locate but both locate and xargs have a way of getting around that. They can both choose to use the \0 null character as a delimiter instead of return lines. Yay. In short, your command becomes:

locate -0b libavfilter.so | xargs -0 rm

Best Answer

Related Solutions

Ubuntu – List all files that do not have extensions

Ubuntu – how to remove files in a list of paths easily

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