Determine if relative or absolute path in shell program
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As stated in the title, I need to determine when a program is ran if the path is relative or absolute:

    ./program #relative
    dir/dir2/program #relative
    ~User/dir/dir2/program #absolute
    /home/User/dir/dir2/program #absolute
    

This are my test cases. How exactly could I go about doing this in a shell program? 