What is the meaning of !#:* !#:1- in a bash command?

Question

In the following Bash command, what is the meaning of: !#:* !#:1

echo "This is a sentence." !#:* !#:1- >text3

Answer 1

It's using bash's history substitution mechanism.

Specifically, !# refers to the current line (up to but not including the location of the !# itself). !#:* is the part of that line after the command name (so, in this case, "This is a sentence."). !#:1- is the same as !#:* except that it omits the last word (so it doesn't include the second copy of "This is a sentence" that we just added via the !#:*).

The end result is a line with three copies of This is a sentence. echoed into a file named text3.