Use of uninitialized value at?

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

Hello

I am using the DBI to grab some data from a database. Some of the database table fields are NULL. I am receiving this error

Use of uninitialized value at /test/getform.cgi line 47

Here is the code

43  $sth=$dbh->prepare("select * from names where id=?");
44  $sth->execute($poreq);                                      
45  my @ar = $sth->fetchrow_array();                            
46          foreach $ar (@ar) {                                 
47                  print "$ar \n";                             
48          }                                                   
49  $sth->finish;
[download]

How do I prevent the error without dropping the perl -w option? Or do I need to put in an code to check the value of $ar in the foreach loop?

Many thank yous...

He who laughs last, doesn't get the joke.

Comment on Use of uninitialized value at? Download Code

Replies are listed 'Best First'.
Re: Use of uninitialized value at? by chromatic (Archbishop) on Oct 08, 2002 at 19:15 UTC
In versions 5.6 and later, you can use `no warnings 'uninitialized'` to suppress that error. In prior versions, you can localize a warnings handler (`$SIG{__WARN__}`) to suppress that error. Otherwise, you have several options. Use a map block to set each element in the array to a null string if it's not defined. Skip undefined elements in the loop. Turn undefined elements into blank strings within the loop.	[reply] [d/l] [select]
Re: Re: Use of uninitialized value at? by grantm (Parson) on Oct 09, 2002 at 10:08 UTC
And in versions before 5.6 you can use the $^W global. eg: `{ local($^W) = 0; # suppress warnings ... your code here ... }` [download]	[reply] [d/l]
Re: Use of uninitialized value at? by kabel (Chaplain) on Oct 08, 2002 at 19:15 UTC
one common idiom: `defined $val or $val = "";` then $val is at least defined, and no warning appears. HTH	[reply] [d/l]
Re2: Use of uninitialized value at? by blakem (Monsignor) on Oct 09, 2002 at 04:09 UTC
Or, since we want to apply this rule to a list: `$_ = '' for grep !defined, @arr;` [download] -Blake	[reply] [d/l]
Re: Use of uninitialized value at? by dpuu (Chaplain) on Oct 08, 2002 at 20:42 UTC
Another alternative is to "catch" the warning: `local $SIG{__WARN__} = sub { warn @_ unless $_[0] =~ /uninitialised/; };` [download] --Dave	[reply] [d/l]
Re: Use of uninitialized value at? by BrowserUk (Patriarch) on Oct 08, 2002 at 19:17 UTC
Done better (and correctly) above.	[reply]
Re: Re: Use of uninitialized value at? by Chmrr (Vicar) on Oct 08, 2002 at 19:19 UTC
..as well as prevent seeing any columns that are zero, the empty string, and so on. `print "$ar \n" if defined $ar;` is probably the way to go in this case. perl -pe '"I lo`+$^X$\"$]!$/"=~m%(.)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'	[reply] [d/l]