If your goal is to safely edit a file, without suffering nasty race conditions, the straightforward solution I concocted back in 2003 (and am still happy with) is to simply write a new file on the same file system ... and then use (atomic) rename to clobber the original file - but only after the new file has been successfully written. This is described in detail at:

In reply to Re: Using the file handle created by File::Temp to set specific file permissions by eyepopslikeamosquito
in thread Using the file handle created by File::Temp to set specific file permissions by mldvx4

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