How comes 'test -n' returns 'true' in bash? -

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I was wondering how it comes 

  test -n  < / Pre> 
 returns 'true', for example:  
  if test -n; Then echo "yes"; Else "No" echo; Fi   
 "Yes" prints, even if the test is given, theoretically, there is an option with an empty-length string with -n option, which checks that String length is 0 false) or something else (true returns).  
 Thanks   
 
 
 This gives the correct  test x for the same reason  Returns correct - string  -n  is non-empty This is not using the  -n  option because  -n  is second Logic is required and you have not provided one.  
  test -n "" || Echo false x = "" test -n $ x & amp; Amp; Test the truth- n "$ x" || False echo   
 Each echo command executes; Note, in particular, in the middle!

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