Question

I’m noticing weird behavior in Bash regarding redirection and can’t explain it. When I type

ls <>a

the current directory’s files print to stdout (Bash shell), the file a is created and is left empty. I would expect an error because no input file was ever specified.
When I type

ls >< a

I get an error (unexpected token ‘<‘). Seems to me that, if the first thing happens, this should attempt to use file a as input to ls. This feels inconsistent.
Doing

ls <>

gives me an error (unexpected token ‘newline’)

 ls ><

gives me a different error (unexpected token ‘<‘)

Can anybody explain what’s happening here?

Answer 1

<> is a valid bash operator, not consecutive < and > operators. >< isn’t a valid operator, so it does get interpreted as consecutive > and < operators. Check the man page:

The redirection operator

[n]<>word 

causes the file whose name is the
expansion of word to be opened for both reading and writing on file
descriptor n, or on file descriptor 0 if n is not specified. If the
file does not exist, it is created.