is_dir_on_path.sh

# Returns true (0) if $1 is on $PATH, false (1) otherwise
# Handles path expansions as expected
# Example: is_dir_on_path ~/bin

is_dir_on_path()
{
    local path
    local dir
    
    # convert $PATH to array
    IFS=':' read -r -a path <<<$PATH
    
    for dir in ${path[@]}; do
        eval dir=${dir} #expands ~
        [ "${dir}" == "${1}" ] && return 0
    done
    
    return 1
}