Solution
This prints the Windows' clipboard to stdout:
powershell.exe Get-Clipboard
Examples
$ echo "hello" | clip.exe
$ powershell.exe Get-Clipboard
hello
$ date +%Y-%m-%d | clip.exe
$ powershell.exe Get-Clipboard
2019-06-13
$ alias paste.exe='powershell.exe Get-Clipboard'
$ echo "world" | clip.exe
$ paste.exe
world
paste() { # Add me to your .bashrc, perhaps.
powershell.exe Get-Clipboard | sed 's/\r\r$//'
# The `sed` will remove the unwelcome carriage-returns
}
source: https://github.com/Microsoft/WSL/issues/1069#issuecomment-391968532