Actually, tail -c counts from the end of the file backwards.
Here is exactly how it works:
1. Simple Counting (Last X Bytes)
When you use a command like tail -c 5, the computer:
- Goes to the very last byte of the file.
- Moves backward 5 bytes.
- Prints everything from that point until the end.
2. Why -c1 vs -c2 matters in your case
As you saw in the lab, tail -c1 showed "nothing" while tail -c2 showed !. Here is the byte-by-byte visual of the end of /tmp/hello:
| Byte Position | Character | Visible? |
|---|---|---|
| Last-1 | ! |
Yes |
| Last (End) | \n (Newline) |
No (it's just a "return" instruction) |
tail -c1: Grabs only the\n. Your terminal moves to a new line, but you see no text.tail -c2: Grabs!AND\n. You see the!.
3. The "Hidden" Offset Mode (+)
Interestingly, tail -c has a "secret" mode. If you put a plus sign before the number, it counts starting from the beginning instead of the end:
tail -c +5: This tells Linux, "Skip the first 4 bytes and show me everything from the 5th byte to the end of the file."
Summary
- Without
+: Count backward from the end (show the last X bytes). - With
+: Count forward from the start (skip the first X-1 bytes).
In most daily tasks, people use it without the + to quickly check the "footer" or trailing metadata of a data file
