Re: FileHandle: undef vs close

[Crackers2]

They're not 100% identical, as the following code shows:

use warnings;
use FileHandle;

$fh = new FileHandle "file", "r";
if (defined $fh) {
  print <$fh>;
  undef $fh;       # automatically closes the file
}

$fh2 = new FileHandle "file", "r";
if (defined $fh2) {
  print <$fh2>;
  close $fh2;       # automatically closes the file
}

print <$fh>;
print <$fh2>;

Output:

Use of uninitialized value in <HANDLE> at t line 16.
readline() on unopened filehandle at t line 16.
readline() on closed filehandle GEN1 at t line 17.

Doing a close seems to maintain some information about the filehandle, and the variable stays defined. Doing an undef unsurprisingly undefs the variable, so you get a slightly different warning, and an extra one about it being udnefined.