Hi Chris!
On Friday 05 Feb 2010 11:56:49 Chris Coggins wrote:
> I posted a question to this list yesterday from the google groups
> interface, asking for help with the following. I have since tried to
> post additional details in replies to that message using the google
> groups site and none of my posts have shown up on the list so let's try
> this again the right way.
>
> I have a datafile with 1 line of data, 30 numbers delimited by tildes.
> (Sample code below only uses 4 numbers to save time)
>
> I need to open this file, grab this line of data, split it into
> individual numbers, perform some simple math (addition) on each
> number, and then put the new values back into the datafile, replacing
> the original data that was there.
>
> I neglected to mention in my original post that I need to access these
> new values elsewhere in the script to perform additional math functions
> with them.
>
> I've tried several variations of the code below, including using arrays,
> and none of them got through without the script failing. The new
> datafile gets written, but it merely contains a ~. The errors I get are
> "use of uninitialized values in such and such line" and "variables needs
> explicit package name". When the script does run, the variables lose
> their values as soon as I close the file after inhaling it, making all
> the rest of the actions in the subroutine futile.
>
> the datafile used below initially contains 30 values that were written
> previously, and this has been verified over and over.
>
Commenting on your code. Also, did you try using the Perl debugger ("perl -d")
to debug the code?
> sub newValues {
> my($file) = shift;
>
1. Your code needs indentation.
2. Either do:
<<
my $file = shift;
>>
Or:
<<
my ($file) = @_;
>>
Otherwise, it is confusing and the meaning may be lost.
> open(FILE, "<$file") or die("Unable to open data file.");
1. Don't use bareword filehandles - use lexicals.
2. Use three args open -
open my $fh, "<", $file or die...;
> while (<FILE>) {
Better do while (my $line = <FILE>) instead of relying on $_.
> my($a,$b,$c,$d) = split(/~/, $_);
Don't call your lexical variables $a and $b - they are special built in
variables. And you probably want an array here.
> $a = $a+$previousarray[4]; # I've tried to perform this math action
> after close(FILE) and get the same result -> failure.
> $b = $b+$previousarray[7];
> $c = $c+$previousarray[0];
You are updating the values of $a, $b, and $c, but they:
1. Will disappear after the loop has exited.
2. Won't be available after the loop's exit.
> }
> close(FILE);
> open(FILE, ">$file") || die ("unable to open file");
Again, see my remarks about open.
> print FILE ("$a~$b~$c \n");
Are you using "strict" and "warnings"?
Regards,
Shlomi Fish
> close(FILE);
> }
> #end sub
>
> Now my datafile just contains a single tilde and no values. I've also
> tried to bring the original data from the datafile into my(@array) and
> get the same errors.
>
> Keep in mind I need other subroutines to be able use these new values,
> but these local variables lose their values once the file is closed.
> I've also tried to declare them as global variables but I'm not doing
> something right because the script won't execute.
>
> I really need some help figuring this out if somebody would be kind
> enough to help a novice.
--
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