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Full Discussion: PERL annoying scope problem
Top Forums Shell Programming and Scripting PERL annoying scope problem Post 302765893 by yifangt on Sunday 3rd of February 2013 07:01:45 PM
Old 02-03-2013
PERL annoying scope problem
Hello,
I met a problem with following code:
Code:
#!/usr/bin/perl -w
# test.pl

use strict;
use diagnostics;
use DBI;

my $dbh = DBI->connect(
"DBI:mysql:BibleBook","yifangt","password")
    or die("Cannot connect: $DBI::errstr");

    my $sql = qq(SELECT * FROM library WHERE isbn = '1234512345');

    my $sth = $dbh->prepare($sql);

    $sth->execute;

    while(my $record = $sth->fetch){
        for my $field (@$record){
        print "$field\n";
    }
        print "\n\n";
}

which looks fine and was running successfully except an warning message:
Code:
"Use of uninitialized value $field in concatenation (.) or string at test.pl line 20. "

The diagnostics tells me the problem is with line 20 and I googled around and, found it is a very popular scope problem with $field, which actually should be related to @$record. But,
1)$record was declared, so was $field;
2)how the scope change within the while and for loops, or/and outside the while loop? which is what I am not sure about;
3) the interesting thing is not every line of the loop issued the same warning. Why?
Can anybody tell me exactly what was wrong in my case and the correct way to eliminate this warning?
Thanks a lot!
 

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LEARN ABOUT MOJAVE

set_color

set_color(1)							       fish							      set_color(1)

NAME

       set_color - set_color - set the terminal color

set_color - set the terminal color
   Synopsis
       set_color [-v --version] [-h --help] [-b --background COLOR] [COLOR]

   Description
       Change the foreground and/or background color of the terminal. COLOR is one of black, red, green, brown, yellow, blue, magenta, purple,
       cyan, white and normal.

       o -b, --background Set the background color

       o -c, --print-colors Prints a list of all valid color names

       o -h, --help Display help message and exit

       o -o, --bold Set bold or extra bright mode

       o -u, --underline Set underlined mode

       o -v, --version Display version and exit

       Calling set_color normal will set the terminal color to whatever is the default color of the terminal.

       Some terminals use the --bold escape sequence to switch to a brighter color set. On such terminals, set_color white will result in a grey
       font color, while set_color --bold white will result in a white font color.

       Not all terminal emulators support all these features. This is not a bug in set_color but a missing feature in the terminal emulator.

       set_color uses the terminfo database to look up how to change terminal colors on whatever terminal is in use. Some systems have old and
       incomplete terminfo databases, and may lack color information for terminals that support it. Download and install the latest version of
       ncurses and recompile fish against it in order to fix this issue.

Version 1.23.1							  Sun Jan 8 2012						      set_color(1)
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