NB - If there are
any further questions about this answer please comment.
There's nothing wrong with the other answers, this one leverages a system command to convert the text file to a compatible filetype for Preview (i.e. PDF).
Given a sample file you can run:
cupsfilter info.txt > info.pdf
(to hide the debug output use
cupsfilter info.txt > info.pdf 2> /dev/null)
After which one may apply the original answer to open the new
info.pdf file in Preview. You can learn more by running
man cupsfilter. I believe this just exposes the basic Save As PDF functionality that exists in the CUPS print system.
As noted in the comments one can simply pipe the command to open a file directly into Preview. This worked for me:
cupsfilter info.txt 2> /dev/null | open -f -a Preview
To open a supported Preview file from Terminal, such as pdf, png, jpg, gif, tiff, bmp:
open -a Preview <nameOfSupportedFileType>
So for example:
open -a Preview avatarMask@2x.png
Opens the png from the current folder in Preview.