bashquine

Shortest non-null bash quine

The shortest bash quine is the null string:

$ bash -c ''
$

What is the shortest non-null bash script which produces its own source code as output?

Solution

  • 19 characters:

    $echo 'echo $BASH_COMMAND' > quine
$ wc -c quine
19 quine
$ cat quine
echo $BASH_COMMAND
$ bash quine
echo $BASH_COMMAND
$

    The character count includes the newline in the source (because it is produced in the output).

    If you've not heard of $BASH_COMMAND before, the manual says:

    BASH_COMMAND

    The command currently being executed or about to be executed, unless the shell is executing a command as the result of a trap, in which case it is the command executing at the time of the trap.