in reply to Re^2: warning: use of uninitialized value
in thread warning: use of uninitialized value

Hello mrityunjaynath,

If you say split(/X/, $string), then $string is split into chunks separated by whatever is matched by X. For example, in this one-liner:

18:05 >perl -MData::Dump -wE "my $s = 'Hello1234world!5678How9012are34
+56you?'; my @w = split /[0-9]{4}/, $s; dd \@w;"
["Hello", "world!", "How", "are", "you?"]

18:06 >

[download]

the string is split on 4-digit groups, and the array @w is populated with the words in $s which come between those digits.

To capture the digit groups, you could try to split on non-digits, but it’s much better (and more straightforward) to use a regular expression with a /g modifier, like this:

open(my $CFILE, '<', 'config.txt') or die "Couldn't open file 'config.
+txt' for reading: $!";
$readline = <$CFILE>;
@words = $readline =~ /([0-9]{4})/g;

[download]

as demonstrated in this one-liner:

18:06 >perl -MData::Dump -wE "my $s = 'Hello1234world!5678How9012are34
+56you?'; my @w = $s =~ /([0-9]{4})/g; dd \@w;"
[1234, 5678, 9012, 3456]

18:18 >

[download]

See split and perlretut.

Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^4: warning: use of uninitialized value
by mrityunjaynath (Acolyte) on Jun 25, 2015 at 09:47 UTC

    hii athanasius i have tried something on the above code . its working but when i have printed $chipID it prints cChipId and $cSubVersId gives 1925 (in last two lines of code ) while the value i have provided through config text ChipId 1925 and SubVersId 0003. so its problemetic output. no warning this time though 

    my @words;
my $readline;
my $cChipId;
my $cSubVersId;
if(open (my $CFILE,"config.txt" ) || die "couldnt open file:", $! ) {
   $readline = <$CFILE>;
    chop($readline);
   if (defined $readline ) {
        @words = split(/ /,$readline);
        $readline = <$CFILE>;
        chop($readline);
      }
   $cChipId = $words[0];
   $cSubVersId = $words[1];
   print "$cChipId \n";
   print "$cSubVersId \n";
}

    [download]
    thanks

[reply]
[d/l]

      Ok, so I understand that the first line of the file “config.txt” is as follows:

      chipid 1925 subversid 0003

      [download]

      It seems you have now chosen to split on whitespace; in which case, it’s safer to use:

      @words = split /\s+/, $readline;

      [download]

      as this will split on one or more consecutive spaces (or tabs, etc.). This will result in the array @words containing four elements: chipid, 1925, subversid, and 0003. The following one-liner demonstrates this:

      23:29 >perl -MData::Dump -wE "my $s = qq[chipid 1925 subversid 0003\n]
+; my @w = split /\s+/, $s; dd \@w;"
["chipid", 1925, "subversid", "0003"]

23:30 >

      [download]

      So, in this case (and remembering that array subscripts begin at zero), the values you want are in $words[1] and $words[3].

      BTW, why do you read the second line from $CFILE into $readline, when that second line is never used?

      Hope that helps,

      Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

[reply]
[d/l]
[select]

        I think the Cookbook recommends an even easier and more reliable method for splitting on white space:

        my @tokenarray = split ' ', $anystring;
[reply]
[d/l]
        hi Athanasius,

        actually the config file read like this ChipId 1925 SubVersid 0001 thats the reason i have read second line... what i want is to take only numeric value but its not happening the code being the same that i have posted you 

        my @words;
my $readline;
my $cChipId;
my $cSubVersId;
if(open (my $CFILE,"config.txt" ) || die "couldnt open file:", $! ) {
   $readline = <$CFILE>;
    chop($readline);
   if (defined $readline ) {
        @words = split(/::/,$readline);
        $readline = <$CFILE>;
      }
   $cChipId = $words[0];
   $cSubVersId = $words[1];
   print "$cChipId \n";
   print "$cSubVersId \n";
}

        [download]
        when i am reading $words[0] and $words1 its giving chipid and 1925...ok .....but when i am reading $words1 and $ words3 it takes nothing for $words3 and shows warning line uninitialized value for $cSubVersId....please help

[reply]
[d/l]

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