ubuntuのcommand_not_found_handle

ubuntuは入力したcommandが見つからない、かつそのcommandがaptで用意されているときに、apt-getしたら入るよ、と教えてくれる。

$ sl
The program 'sl' is currently not installed.  You can install it by typing:
sudo apt-get install sl
-bash: sl: command not found

どやってるのかな？と思って環境変数とかmanとか見てたら、debianの拡張らしいすね。

• man bash

command_not_found_handle
   The  name  of  a shell function to be called if a command cannot be found.
   The return value of this function should be 0, if the command is available
   after  execution  of  the  function, otherwise 127 (EX_NOTFOUND).  Enabled
   only in interactive, non POSIX mode shells. This is a Debian extension.

$ set
(略)
command_not_found_handle ()
{
    if [ -x /usr/lib/command-not-found ]; then
        /usr/bin/python /usr/lib/command-not-found -- $1;
        return $?;
    else
        return 127;
    fi
}

$ file /usr/lib/command-not-found
/usr/lib/command-not-found: python script text executable