Linux

Oneliner functions count too, right?

binexist() {
	##: lookup input in PATH, returns bool true/false
#	IFS=:; find $PATH -executable -name "$1" 2>/dev/null |grep -q "/$1$" # slower
	command -v "$1" >/dev/null 2>&1
}
contains() {
	##: finds term in string, returns true/false
	##: $ contains <search term> <string>
	case "$1" in *${2}*) return 0;; *) return 1;; esac
}

error() {
       ##: complain to STDERR and exit if given code 
        printf '%s\n' "$1" >&2; [ -n "$2" ] && exit "$2"
}

random() {
	##: generate random number of <input> length
	test "$1" -gt 1 && shuf -i 0-9 -n"$1" |tr -d '\n'
}

nfoview() {
	##: view nfo files like intended
	iconv -f CP866 <"$1" |less
}

mod_preset() {
	##: print a nicely formatted preset of module options
	modinfo -p "$1" |awk \
		-F':' \
		-v 'module="$1"' \
		'{first=$1; $1="";print "\n#"$0"\n#options module "first"="}'
}

dpv() {
	##: flash image to stick with progress bar, workaround for pv's flash bug #oflag=direct is fastest
	##: https://askubuntu.com/questions/901481/writing-to-disk-using-pv-seems-to-be-fast-at-first-and-slow-at-the-end/961659#961659
	pv "$1" |pkexec dd of="$2" bs=4M oflag=direct iflag=fullblock
}

Not oneliners but still something i want to show off:

functions() {
	##: prints code of function files
	function_s="$(sed '/^$/d;/##[^:]/d' "$SHELL_HOME"/functions)"
	if [ -n "$1" ]
		then echo "$function_s" |sed -n -e "/$1.*{/,/^}/ p" |highlight --line-numbers -qs candy --out-format=xterm256 --syntax=sh --stdout
		else echo "$function_s" |highlight -qs candy --out-format=xterm256 --syntax=sh --stdout
	fi
}

readconf() {
	# reads parameters from config file in param=value note, where '=' is set with $separator
	# format: conf_read <parameter> <replacement> where replacement get's used if parameter is empty
	if [ -f "$cfg_file" ]
		then parm="$(cut -d'#' -f1 "$cfg_file" |grep "$1" |cut -d${separator} -f2- |tr -d '"')"
		else unset parm; fi
	[ "$separator" = "=" ] && printf '%s\n' "${parm:-"$2"}"
}

The readconf function is used like this:

config content:
# this a comment
apple=red
banana=yellow # this too

config=/path/to/config.conf
$ color_apple="$(readconf apple green)"
$ color_banan="$(readconf banana)"

And the 'functions' function looks like this: