bash - Why is a file tested with -r not readable by cat? -

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In this I have a cron job with two lines: 

  LOCK = / var / run / dns-check ... if [! -r "$ LOCK" - "$ ADDR_NOW"! = "$ (Cat $ LOCK)"]; Then   
 This is the only use of  cat  in the script. Today I received the following error from the cron:  
 cat: / var / run / Dns-check: there is no such file or directory  
 I wonder what's happened here.  
 I am checking the file with  -r  so that it is legible and not the result. This means that if the file is not readable, the check is successful. Evaluation can stop here because the expression is already true.  cat  will not be called.  
 Otherwise, the  -o  status is evaluated, which means if the file is executed,  cat  is executed.  
 Why the  cat  reports the error, that the file can not be read, although  test -r  is detected that it is readable?   
 
 
 Using conditional form does not evaluate the short circuit instead, instead, try:  
  [! -r "$ LOCK"] || ["$ ADDR_NOW"! = "$ (Cat $ logical)"]   
 Then the second check will only be if first failed.

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