Symbol that will show up first in output of `ls`?

^, in ASCII order, follows the uppercase letters. - precedes all the letters and digits, but follows several other punctuation characters.

The ASCII printable characters, in order, are:

 !"#$%&'()*+,-./0123456789:;<=>?
@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_
`abcdefghijklmnopqrstuvwxyz{|}~

But this doesn't necessarily help you, since the order in which ls lists files may be affected by the current locale.

You could start the file name with a space or ! character, but that's going to make it difficult to refer to the file without quoting it -- and again, locale settings could interfere. Most of the other ASCII characters that precede the decimal digits will have similar problems.

Your best bet, assuming you don't have other files with odd characters in their names, might be to start the file name with a string of 0s:

 000_DELETED

(I've used a similar technique to name e-mail folders in Thunderbird and Outlook.)

On GNU systems at least in most locales other than C/POSIX, there are a few characters that are ignored with regards to sorting. That's the case for instance of _, ., space or 0x1.

That's why .a, .c, __b, _d sort as .a, __b, .c, _d for instance.

For strings that consist only of those ignored characters, the sort order is defined in the locale, ASCII SPC comes generally first. So a single space character would be the file that sorts first (even before 0x1 (the first one in C locale), . and ..), then 2 spaces... etc. However, <SPC>DELETED would sort after DELETED, so while a file called ___ would sort before most other files, putting ___ in front of some other string doesn't make it sort sooner.

Among the non-ignored characters, ASCII 0 is generally the character that sorts first in non-C locales.

So a file called 0 would sort before any other file than contains non-ignored characters. Prepending 0 to a file that contains non-ignored characters would make it sort earlier in non-C locales.

So a file called $'\01\01\01_000_DELETED' would sort very early in the C locale (because 0x1 is the first character so sorts first), and also in other locales (because all the 0x1, and _ are ignored, but then the 0s are the non-ignored characters that sort first).

In non-C locales, it would still sort after . or ...

Another option could be to write DELETED with only ignored characters like " ₫€£€₮€₫". Those currency symbols are ignored wrt sorting. SPC also sorts quite early in the C locale, so it should sort before . both in C and non-C locales.

$ touch $'   \u20ab\u20ac\u00a3\u20ac\u20ae\u20ac\u20ab' $'\01' ' ' 0normal-file $'\01\01\01_000_DELETED'
$ ls -1a

   ₫€£€₮€₫
./
../
?
???_000_DELETED
0normal-file
$ LC_ALL=C ls -1a
?
???_000_DELETED

   ????????????????????
./
../
0normal-file
$ LC_COLLATE=C ls -1a
?
???_000_DELETED

   ₫€£€₮€₫
./
../
0normal-file