CYGWIN environment variable and its contents have effect on several aspects of the Cygwin environment. If
Cygwin will warn the first time a user uses an "MS-DOS" style path name rather than a POSIX-style path name
as stated by one of Cygwin FAQ pages.
What is first time? Once a day? Once between computer restarts?
I had set
CYGWIN=nodosfilewarning, but still sometimes Cygwin warns me that I use MS-DOS style paths. If I set it to
dosfilewarning (and restart my shell) I can't trigger the warning no matter what (like
cd C:\\Windows—I assume this is MS-DOS-ish enough).
I don't exactly know if the
CYGWIN variable have to be set at OS level or in my Cygwin shell, however I have tried both without success. By without success I mean, if the variable is set to
dosfilewarning my assumption is that Cygwin should warn me every time I type something like
cd C:\\Windows (which it doesn't do).
How can I verify that I set this stupid variable correctly and my settings are in effect? Cygwin's FAQ gives little help on this particular problem.
Thanks to JdeBP's answer I've managed to come to the following conclusion.
CYGWIN variable can be set either at OS level or in a Cygwin shell.
cd C:\\Windows doesn't trigger the warning at hand, but
ls C:\\Windows does (talk about consistency, huh?).
For now, settings
nodosfilewarning really reports no warning for the previously mentioned command, however I originally wrote this post because even though I told Cygwin not to report these warnings it still did sometimes. Unfortunately I don't know when and under what circumstances (I'll update the question if I further encounter these warnings).