How to check if currently running shell is BusyBox

I tried different variants

echo $0
echo $shell
echo $SHELL
ps -p $$

JavaScript
​x
 
echo $0echo $shellecho $SHELLps -p $$​

but none of them can give a distinctive output. I can do something like this but it’s ugly and hackish:

if ls --help 2>&1 | grep BusyBox; then
    echo "it is BusyBox"
else
    echo "it is NOT BusyBox"
fi

JavaScript
 
if ls --help 2>&1 | grep BusyBox; then    echo "it is BusyBox"else    echo "it is NOT BusyBox"fi​

Answer

Another way requiring Linux and readlink:

#!/bin/ash
exe=`exec 2>/dev/null; readlink "/proc/$$/exe"`
case "$exe" in
*/busybox)
    echo "It's a busybox shell."
    ;;
esac

JavaScript
 
#!/bin/ashexe=`exec 2>/dev/null; readlink "/proc/$$/exe"`case "$exe" in*/busybox)    echo "It's a busybox shell."    ;;esac​