I know that if you have a file one.txt in ~/Documents and you cd ~/Documents then realpath one.txt will print:
~/Documents/one.txt.
However what if you want to print the path of a file in a different directory. For example, cd a/b and there is a file two.txt in directories a2/b2 then how does a person print the absolute path of two.txt by just passing two.txt to a command.
Looking to do something like realpath two.txt that works from a different directory.
Just give realpath the relative path from the current directory:
$ pwd
/home/myself/local/build/shell-toolbox
$ realpath ../../../.profile
/home/myself/.profile
The GNU realpath utility would not be able to find my .profile file, or produce the absolute path for it, without me giving it a hint about where it was located. In your case, you could potentially have any number of files called two.txt, so realpath must at least be given a relative path from the current directory to be able to give an absolute pathname for the file.
In a Unix filesystem, a file is uniquely identified by a pathname (either relative or absolute). A filename can not uniquely identify any file other than one of the files in the current directory.
To locate all regular files called two.txt in or under your home directory, and get their pathnames relative to $HOME:
find "$HOME" -type f -name two.txt
realpath the relative path because the file is in a different branch. For example instead of .profile you wanted to query a file in /etc? Perhaps realpath does not have this functionality because the developers wanted to avoid printing the paths of files with the same name but in practice how many files can be identical in name?
realpath for a file that is on a different branch of the directory tree?