"Use of uninitialized value" due to empty elements in an array

michaelp has asked for the wisdom of the Perl Monks concerning the following question:

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Re: "Use of uninitialized value" due to empty elements in an array by chuckbutler (Monsignor) on Mar 31, 2010 at 14:14 UTC
The defined function is what you need. It returns true if the value being tested IS NOT the special undef value. So something like: `unless (defined($line_split[0])) {...} ...` [download] ahead of your other tests should get the job done. Update: Fixed typo.. Good luck. -c	[reply] [d/l]
Re: "Use of uninitialized value" due to empty elements in an array by roboticus (Chancellor) on Mar 31, 2010 at 14:32 UTC
michaelp: If you simply want to turn undefined elements into an empty string, you could add a step to perform the conversion immediately after the split, like so: `@line_split = map { defined($_) ? $_ : '' } split (/\t/, $line);` [download] ...roboticus	[reply] [d/l]
Re: "Use of uninitialized value" due to empty elements in an array by ikegami (Patriarch) on Mar 31, 2010 at 15:27 UTC
Tell `split` not to remove empty trailing fields. `my @line_split = split(/\t/, $line, -1);` [download] And if you want, you can check if you got enough fields `if (@line_split != 3) { die("Not enough fields in line $.\n"); }` [download]	[reply] [d/l] [select]
Re^2: "Use of uninitialized value" due to empty elements in an array by michaelp (Initiate) on Mar 31, 2010 at 17:28 UTC
Thanks for all the help!	[reply]
Re: "Use of uninitialized value" due to empty elements in an array by JavaFan (Canon) on Mar 31, 2010 at 15:06 UTC
`$line_split[0]` will only be undefined if `$line` doesn't contain any other character than `\t` (including being empty). And the fact it's undefined stems from `@line_split` not having any entries. So, you may do something like: `if (@line_split && $line_split[0] eq "") { # Has empty leading fields }` [download] or `if (!@line_split \|\| $line_split[0] eq "") { # Has empty leading fields, or no fields at all }` [download] depending on what you want to do if there are no fields at all.	[reply] [d/l] [select]
Re: "Use of uninitialized value" due to empty elements in an array by GrandFather (Saint) on Mar 31, 2010 at 19:57 UTC
'tab-delimited file' translates to CSV file (comma separated files are common) and there are standard ways to handle such beasts. It may well be that your files are trivial and split will work fine, but in the general case there are many nasty edge cases to take care of with such files. Take a look at Text::CSV and Text::xSV. True laziness is hard work	[reply]