CETX_var_log

Indeed, *most* material I've read also shows the example with the dash, but never explains its purpose. Usually what happens is you learn you don't need the dash, so start omitting it, unaware that you're not pulling in that user's environment variables when you do so.

This is mostly an issue when you su from a regular user to root, a la "su -", on a system that doesn't include /sbin/ and /usr/sbin in a regular user's PATH by default. Just using a plain "su" becomes an exercise in frustration when you're switching to root to be able to run some sys admin commands typically located in one of these two directories.

Why did the creators of "su" decide to use an oddball switch like "-" for this purpose? I haven't a clue. With most other commands, supplying a "-" explicitly tells that command to read from STDIN. This is useful for supplying arguments to a switch on one command with the output from another (ex: "find . -name 'expressions.txt' | grep -f - file.txt" - which means search for a file called expressions.txt, and have the grep command use it as a list of regular expressions to execute on the file file.txt).

thanks for the info. very cool.