Diagnose watch utility

Question

I have a script that runs in the background which uses watch to monitor a directory for changes. This works just fine. However, I had a need for the script which runs the monitoring script to be run as daemon. The daemon is running as the same user, but now watch is returning "1 Various failures."

I suspect that there is some environment variable that is not set right, but there are too many to use trial and error to diagnose the issue. And unfortunately, "Various failures" is not very helpful. Any ideas how I might diagnose this?

The command is

watch -d -t -g ls -l

I think something like the following can be used as a work-around.

diff <(ls -l) <(sleep 1; ls -l)

Answer 1

I finally discovered the following on stderr.

Error opening terminal: unknown.

It was easily resolved by the answer to error opening terminal. So it did turn out to be an environment variable. I don't see this error message in the code. Perhaps it occurs when making a system call that needs the terminal.