How can I tell whether I'm in a screen?

Question

When using screen in linux, how can I tell if I\'m in a screen or not? I could do exit and I\'ll exit a screen if I was in one, but if I wasn\'t, then I\'ll end

Answer 1

Since all of the other methods here rely on environment variables (which can simply be overridden) or the command character for screen (which can also be overridden), the most foolproof way to check would be to list all the ancestors of the current process.

pstree --show-parents -p $$ | head -n 1 | sed 's/\(.*\)+.*/\1/' | grep screen | wc -l

If it prints 1, then the current process you're running has an ancestor with the word 'screen' in the executable's name, otherwise there wasn't.

A more facile visible inspection might be obtained from:

pstree --show-parents -p $$ | head -n 1 | sed 's/\(.*\)+.*/\1/' | less