du -sh and ls -l

In short, du (disk usage), list the size actually that file occupied, system use block to store data, each block is 4k, so even if you have a 10 bytes file, it will still use 4k disk usage, so du file shows 4k. But if you use ls -l, it shows 10 bytes.
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Create file

 ~/Learning/Programming/C_Cpp  on main +1 !1 ?5                 at 04:40:25 PM ─╮
❯ dd if=/dev/zero of=./test bs=1040 count=1                                       ─╯
1+0 records in
1+0 records out
1040 bytes (1.0 kB, 1.0 KiB) copied, 0.00037525 s, 2.8 MB/s

ls -l

 ~/Learning/Programming/C_Cpp  on main +1 !1 ?5                 at 04:40:42 PM ─╮
❯ ls -l test                                                                      ─╯
.rw-r--r-- 1.0k coolder  8 Oct 16:40 test

du -sh

 ~/Learning/Programming/C_Cpp  on main +1 !1 ?5                 at 04:41:22 PM ─╮
❯ du -sh test                                                                     ─╯
4.0K    test