How to locate and display a file
xdg-open doesn't read from stdin. Use
locate X | xargs -L1 xdg-open
You need to use:
xdg-open "$(locate X)"
If your file contains spaces/special characters you need to use:
xdg-open "$(locate "X")"
Note: This command must be directly used in terminal. Use of this command in shell scripting need to be avoided as it may generate errors or inconsistent outputs.