in reply to Re^4: warning: use of uninitialized value
in thread warning: use of uninitialized value

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

chipid 1925 subversid 0003

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

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

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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 >

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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,

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Re^6: warning: use of uninitialized value
by u65 (Chaplain) on Jun 25, 2015 at 17:14 UTC

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

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

      You don't even need to go as far as the cookbook for that, it's right there in the documentation for split:

      As another special case, split emulates the default behavior of the command line tool awk when the PATTERN is either omitted or a literal string composed of a single space character (such as ' ' or "\x20" , but not e.g. / / ). In this case, any leading whitespace in EXPR is removed before splitting occurs, and the PATTERN is instead treated as if it were /\s+/ ; in particular, this means that any contiguous whitespace (not just a single space character) is used as a separator. However, this special treatment can be avoided by specifying the pattern / / instead of the string " " , thereby allowing only a single space character to be a separator. In earlier Perls this special case was restricted to the use of a plain " " as the pattern argument to split, in Perl 5.18.0 and later this special case is triggered by any expression which evaluates as the simple string " " .
[reply]

        Right you are! And that special behavior from split ' ' is why early on I made that my standard ws splitting idiom except in unusual cases.

[reply]
[d/l]
Re^6: warning: use of uninitialized value
by mrityunjaynath (Acolyte) on Jun 26, 2015 at 04:00 UTC
    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]
      Hello mrityunjaynath,

      Athanasius gave you the right advice about picking the correct values off split. What you need to realize is, arrays are indexed from zero: if you have an array @myarray with 3 elements, it will have elements at: $myarray[0], $myarray[1] and $myarray[2]. Also, why are you splitting on :: when you have specified the config file to be delimited by spaces? 

      $ cat pm_1132055.pl
#!perl

while(my $line = <DATA>) {
    chomp $line;
    my @words = split /\s+/, $line;
    print join(", ", @words), "\n";
    print qq{\$words[1] --> $words[1] and \$words[3] --> $words[3]}, "
+\n";
}



__DATA__
ChipId 1925 SubVersid 0001

$ perl pm_1132055.pl
ChipId, 1925, SubVersid, 0001
$words[1] --> 1925 and $words[3] --> 0001

      [download]
      Now, consider what you have done: 
      $ cat pm_1132055.pl
#!perl

while(my $line = <DATA>) {
    chomp $line;
    my @words = split /::/, $line;
    print join(", ", @words), "\n";
    print qq{\$words[1] --> $words[1] and \$words[3] --> $words[3]}, "
+\n";
}



__DATA__
ChipId 1925 SubVersid 0001

$ perl pm_1132055.pl
ChipId 1925 SubVersid 0001
$words[1] -->  and $words[3] -->

      [download]
[reply]
[d/l]
[select]

        my fault...i have less knowledge of html so not able to write properly..what i want to say is my config file reads like this,
        chipId::1925
        subversid::0001
        now this is creating the above stated problem

[reply]

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