Is there some shell full path function?

Question

Is there some native function(shell, linux command) to merge/compute the full path?

example:

old_path="~/test1/test2/../dir3//file.txt"
new_path=FUN($old_path)

echo "$new_path"   // I want get this "/home/user/test1/dir3/file.txt"    

Answer 1

Use readlink:

$ readlink -m ~/foo.txt
/home/user/foo.txt
$ readlink -m ~/somedir/..foo.txt
/home/user/foo.txt

It also handles symlinks.