What's Linux test -a command test for?

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http://superuser.com – Please take a look at the following code, snap=snapshot.file touch snapshot.file-1 $ [ -a $snap-1 ] && echo yes yes What does the test -a command tests for here? I tried info coreutils 'test invocation' and searched for -a, but didn't find it in the file characteristic tests section, but rather in the connectives for test section. Is such test -a command an undocumented one? NB, Before jump to any conclusion, please make sure you can duplicate the about result first. My system is Ubuntu 13.10 and my man test says GNU coreutils 8.20 October 2012 TEST(1). (HowTos)