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Comment by sillysaurusx | Hacker News Reader

This script taught me a few things! Since it's kind of impossible to google, what does this construct mean?

   while :; do

It's clearly a while true loop, but why does an ascii crying face produce true?

: is a sort of 'null' function in bash and bourne shells. It also always returns 0 so it's an alternative to 'true'.

    $ type :
    : is a shell builtin

Bash also has the equivalent "true" as a builtin, and Coreutils provides one as well, allowing to write this instead:

  while true; do

true is also a POSIX utility (not builtin), so it can be used in POSIX-y sh scripts as well.

The other common idiom in scripts that uses the : is

  : > $LOGFILE

which creates a zero-length log file, and removes the contents if it already existed.

You can search for this.

You get decent results if you put it on quotes.

What's impossible to google about that? "bash colon" gives tons of results

Including the somewhat unexpected "Bottoms Up Bash - Colon Cancer Prevention Project".