Remove files except latest one by numeric order

Question

I am trying to remove files within a bash script.

I can list the latest file with:

ls | grep core | tail -n 1

and rename it like keep-core-2994-xyz.bin, then remove the rest with:

rm -f core-*

and then rename the latest to the original. In this way, I can keep the latest file and remove the rest. This works fine for this scenario:

-rw-------  1 root root  47M Sep  3  2017 core-2994-xyz.bin
-rw-------  1 root root  47M Sep  3  2017 core-3012-xyz.bin
-rw-------  1 root root  79M Sep  3  2017 core-3106-xyz.bin

However, this one: core-10000-xyz.bin causes trouble:

-rw-r--r--  1 root root  55M Sep  3  2017 core-10000-xyz.bin
-rw-------  1 root root  47M Sep  3  2017 core-3012-xyz.bin
-rw-------  1 root root  79M Sep  3  2017 core-3106-xyz.bin

... because this time, I need to keep the one I want with head, not with tail.

Is there any effective way to remove files except the latest one which were created by this order? (Here, core-3012-xyz.bin)

The file timestamps are unreliable; this is an embedded device and timestamps can change due to the internet connection, so I can't list them by timestamp.

This is an embedded device and I don't want to compile it with zsh; I'd like a bash-only solution, please.

Answer 1

With zsh:

rm -f -- *core*(n[1,-2])

Where the n glob qualifier turns on numericglobsort for that one glob expansion and [1,-2] selects the first to second last.

Or:

rm -f core-<1-4294967295>-xyz.bin(n.[1,-2])

If you want to make it more specific, where <1-2147483647> matches on sequences of digits that represent numbers in the range of valid pid numbers and the . qualifier restricts the expansion to regular files only.

Note that core-bar-123 would sort before core-bar-1000 but also before core-foo-1. The numeric sort is used when it comes to comparing numbers when the part leading up to them is the same. Here core-bar sorts before core-foo. Adding numbers to either won't change that.

To only consider the numbers when sorting, you could do something like:

extract_numbers() {
  set -o localoptions -o extendedglob
  REPLY=${${${REPLY//[^0-9]##/-}#-}%-}
}

rm -f --  *<->*(.no+extract_numbers[1,-2])

Where extract_numbers converts some123file5123with3numbers to 123-5123-3 which is then used for numeric ordering.

Answer 2

Oh i found the solution.

ls -v | grep core | tail -n 1

will do the trick.

Reference:

List files sorted numerically