Perl close() is not POSIX close(). Some less-bizarre reasons that Perl close() might fail include:

ENOSPC
A previous write to disk failed because the disk partition ran out of space (and you had not cleared errors for that handle by seek()ing since then).
EPIPE
You had unflushed data and close() tried to flush it and all of the readers at the other end of your pipe/socket have already closed/shutdown their end. Or a previous write to that handle failed for that reason (and you probably got a SIGPIPE earlier).
EIO
Your device has decided to fail. This is more specific than "something is wrong". You should arrange to remember what you had opened so that you can mention that in the "close() failed" error message so the user (or their admin) can determine which device to check.
ECONNRESET
Your socket connection got reset (since the last time you cleared errors by seek()ing).
ENOMEM
The system wanted to allocate more buffer space but the call to allocate that failed (possible at least for sockets).

Plus there are errors that can originate from some I/O layer. You'd have to consult the documentation and/or code for whatever layers you might use for more information on that. Perhaps you can use an encoding layer configured to complain about untranslatable characters via an error return. Or a "decompress" layer might complain about invalid input.

It can be useful to check for close failing because it may be important to not continue on after close() failed because the data you were writing or reading is incomplete and so you shouldn't submit it or shouldn't mark the data source as "done" or whatever.

It is usually easier to check for close() failing than to check every single I/O operation for failure. If using buffered I/O, then checking every single I/O operation wouldn't be sufficient anyway.

If I have no logical recovery step for "incomplete data", then I will just warn when close fails.

- tye        

In reply to Re^5: Scoping question - will file handle be closed? (close errors) by tye
in thread Scoping question - will file handle be closed? by Monk::Thomas

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