parsing data in a file

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

Script

1 #!/usr/bin/perl -w
  2 
  3 use strict;
  4 
 16 while (my $input = <DATA>){
 17 chomp($input);
 18 my ($name,$num,$addr,$date,$n) = split(":", $input);
 19 my ($fname,$lname) = split(" ",$name);
 20 print "$lname\n" if $lname =~ /^ker/;
 21 }
 22 print "\n";
 23 
 24 
 25 __DATA__
 26 Tommy Savage: 408–72 4–0140: 12 2 2 Oxbow Court, Sunnyvale, CA 940
+87: 5/19/66: 34200
 27 Lesle Kerstin: 408–456–1234: 4 Harvard Square, Boston, MA 02133: 4
+/22/62: 52600
 28 JonDeLoach: 408–253–3 122: 12 3 Park St. , San Jose, CA 94086: 7/2
+5/53: 85100
 29 Ephram Hardy: 293–259–5395: 2 3 5 Carlton Lane, Joliet, IL 73858: 
+8/12/20: 56700
 30 Betty Boop: 245–836–83 57: 63 5 Cutesy Lane, Hollywood, CA 91464: 
+6/23/23: 14500
 31 William Kopf: 846–83 6–2837: 693 7 Ware Road, Milton, PA 93756: 9/
+21/46: 43500
 32 Norma Corder: 397–857–2735: 74 Pine Street, Dearborn, MI 23874: 3/
+28/45: 245700
 33 James Ikeda: 834–938–8376: 2 3 445 Aster Ave. , Allentown, NJ 8374
+5: 12/1/38: 45000
 34 Lori Gortz: 327–832–5728: 3465 Mirlo Street, Peabody, MA 34756: 10
+/2/65: 35200
 35 Barbara Kerz: 385–57 3 –8326: 83 2 Ponce Drive, Gary, IN 83756: 12
+/15/46: 268500
[download]

Result


:~/pbe/chap8$ ./exer1.pl 
Use of uninitialized value $lname in pattern match (m//) at ./exer1.pl
+ line 20, <DATA> line 3.
Use of uninitialized value $name in split at ./exer1.pl line 19, <DATA
+> line 11.
Use of uninitialized value $lname in pattern match (m//) at ./exer1.pl
+ line 20, <DATA> line 11.
Use of uninitialized value $name in split at ./exer1.pl line 19, <DATA
+> line 12.
Use of uninitialized value $lname in pattern match (m//) at ./exer1.pl
+ line 20, <DATA> line 12.
Use of uninitialized value $name in split at ./exer1.pl line 19, <DATA
+> line 13.
Use of uninitialized value $lname in pattern match (m//) at ./exer1.pl
+ line 20, <DATA> line 13.
Use of uninitialized value $name in split at ./exer1.pl line 19, <DATA
+> line 14.
Use of uninitialized value $lname in pattern match (m//) at ./exer1.pl
+ line 20, <DATA> line 14.
Use of uninitialized value $name in split at ./exer1.pl line 19, <DATA
+> line 15.
Use of uninitialized value $lname in pattern match (m//) at ./exer1.pl
+ line 20, <DATA> line 15.
[download]

Question

I am very confused with uninitialized errors, can anyone explain how to fix it. thanks!!

Comment on parsing data in a file Select or Download Code

Replies are listed 'Best First'.
Re: parsing data in a file by tirwhan (Abbot) on Nov 02, 2010 at 14:12 UTC
Take a close look at the error messages and the lines in your data the error messages correspond to. You'll see that on line 3 of your data the name is JonDeLoach, so there is no whitespace for your second split to split on, and hence no data in $lname. As for lines 11 and subsequent of your data...well, I'm sure you can easily see what's wrong with them. All dogma is stupid.	[reply] [d/l]
Re: parsing data in a file by johngg (Canon) on Nov 02, 2010 at 15:06 UTC
Note also that you are trying to print a last name if it matches the regex `/^ker/` but regexen are case-sensitive. Unless you either supply the `i` flag (`/^ker/i`) to ignore case or make your pattern more accurate (`/^Ker/`) you will never get a match as your last names start with an upper-case letter. Cheers, JohnGG	[reply] [d/l] [select]
Re: parsing data in a file by talexb (Chancellor) on Nov 02, 2010 at 16:46 UTC
You should be programming defensively here: `my ($fname,$lname) = split(" ",$name);` Instead of that, I'd recommend `# If there are two names separated by a space .. my ($fname,$lname); if ( $name =~ /\w+\s\w+/ ) { # Separate them into first and last names. ($fname,$lname) = split(" ",$name); } else { # Otherwise, decide what to do with just a single name. # Use the name as a last name? Die? Ignore? }` [download] Don't assume that your input's always going to be clean. Alex / talexb / Toronto "Groklaw is the open-source mentality applied to legal research" ~ Linus Torvalds	[reply] [d/l] [select]
Re: parsing data in a file by kcott (Archbishop) on Nov 02, 2010 at 14:54 UTC
Take a look at split - the first argument is actually a regular expression. Looking at your data, `split(":", $input)` should probably be `split(/: /, $input)` (i.e. a colon followed by a space). -- Ken	[reply] [d/l] [select]
Re^2: parsing data in a file by CountZero (Bishop) on Nov 02, 2010 at 15:36 UTC
And as sometimes TAB characters hide themselves as whitespace, I usually write such regexen as `/:\s+/` CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James	[reply] [d/l]
Re^3: parsing data in a file by kcott (Archbishop) on Nov 02, 2010 at 15:44 UTC
Good point, CountZero. And a requirement in more complex REs that you've spaced out for readability: `/ : \s+ /x` (a bit over-the-top for that example but it shows the intent :-) -- Ken	[reply] [d/l]


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