one-line self-executing c header and expanded explanation

expanded.md

//

Since we don't want this visible in C, we put it in a comment.

&>/dev/null

Unfortunately // is interpreted as an invalid shell command and produces an error message, so we need to redirect that to /dev/null to get rid of it.

;x="${0%.*}"

This determines what our compiled filename will be by using string replacement to get rid of any extensions on the current filename.

;[ ! "$x" -ot "$0" ]||

This check if there already is a compiled version newer than the source file. If not...

(rm -f "$x";cc -o "$x" "$0")

...we delete any existing version and then compile our code, using our chosen compiled filename.

&&exec "$x" "$@"

If the compile was successful or unnecessary, pass execution to the compiled code, passing on the arguments given to this script.

original.bash

//&>/dev/null;x="${0%.*}";[ ! "$x" -ot "$0" ]||(rm -f "$x";cc -o "$x" "$0")&&exec "$x" "$@"