How can I sort lines in a text file without changing the original?

First, preview the result without redirecting it into a file. On a system with GNU Coreutils, open a terminal in the file’s folder and run:

sort notes.txt

Replace notes.txt with your file’s name. GNU sort reads the named file and, by default, writes its sorted output to standard output rather than replacing the input file. [S1] That means the command displays a result; it does not, by itself, save that result over the original. This behavior is documented for GNU sort, not every system’s utility, so check which sort your system provides before relying on it.

Suppose notes.txt contains these lines:

pear
Apple
banana

Running sort notes.txt prints an ordered version in the terminal, while the file remains your input. Before saving, compare the displayed lines with what you expect: are all the lines present, and does the order look right for your task? GNU sort compares whole lines by default, and the active locale’s character-collating sequence can affect ordering. [S1] So don’t assume that capitalization, punctuation, accents, or other characters will sort exactly as you expect; verify the preview on your own system.

Write the output to a different filename, for example:

sort notes.txt > notes-sorted.txt

Here, notes.txt is the input and notes-sorted.txt is the separate output. Check that the output name is not the same as the input name: redirecting output to the original path is not a safe way to preserve it. If notes-sorted.txt already exists, choose a new name or decide deliberately whether to replace that separate file. Then inspect the saved copy and, if needed, compare it with the original. This example assumes a shell and GNU sort; other tools may differ.

Yes. You can try a different documented option on a preview, but check what that option means for your particular sort implementation before using it. GNU sort supports options that change keys or ordering, and locale also affects comparison. [S1] The right setting depends on your language, file format, and goal; the behavior described here does not cover every platform’s command. Keep the input path unchanged, preview each variation without redirection, and save only a result you have checked under a different filename. If you need a specialized order, consult your system’s utility documentation.