Output Repeats in the elsif statement

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

The elsif statement repeats the output and I am not sure why

sub viewrailcarsroadname{
no warnings 'redefine';
no warnings 'uninitialized';
print color 'green';

open(MYINPUTFILE, "railcardata.txt"); # open for input
$| = 1;
my @lines = <MYINPUTFILE>; # read file into list
close (MYINPUTFILE);

printf ("                         ===============================\n\n"
+); 
printf ("                         |     VERIFY CAR ROAD NAME    |\n\n"
+); 
printf ("                         ===============================\n\n"
+);
printf ("                                                        \n\n"
+); 
printf ("                        PLEASE INSERT ROADNAME TO VERIFY:\n\n
+");
printf ("                                \n\n\n\n\n\n\n\n");

my $carroadnameverify = <STDIN>; 
chomp($carroadnameverify); 

printf ("\n         ==================================================
+=================\n\n");
printf ("         | ROAD NAME  |  ROAD NUMBER  |  CAR TYPE  |  INTERCH
+ANGE RAILROAD |\n\n");
printf ("         ====================================================
+===============\n\n\n");

foreach my $carroadnameverify2 (@lines) {
if ($carroadnameverify2 =~ /$carroadnameverify/) {
my $format = "           %-13s %-15s %-12s %0s";
printf ("$format", split/\:/, "$carroadnameverify2");
} elsif ($carroadnameverify2 =~ '') {
printf ("CAR RECORD NOT FOUND");
} 

} # END FILE LOOP

printf ("\n\n\n\n                     WHEN YOU ARE DONE VIEWING HIT RE
+TURN TWICE:\n\n\n\n\n\n\n\n");

my $input = <STDIN>;
chomp($input=<STDIN>);
structure::railcar();
} # END VIEW SUB
[download]

Comment on Output Repeats in the elsif statement Download Code

Replies are listed 'Best First'.
Re: Output Repeats in the elsif statement by jwkrahn (Abbot) on Feb 13, 2013 at 21:56 UTC
`if ($carroadnameverify2 =~ /$carroadnameverify/) { ... } elsif ($carroadnameverify2 =~ '') {` [download] From perlop: The empty pattern // If the PATTERN evaluates to the empty string, the last successfully matched regular expression is used instead. In this case, only the "g" and "c" flags on the empty pattern is honoured - the other flags are taken from the original pattern. If no match has previously succeeded, this will (silently) act instead as a genuine empty pattern (which will always match).	[reply] [d/l]
Re: Output Repeats in the elsif statement by Kenosis (Priest) on Feb 13, 2013 at 21:08 UTC
Were you trying to test whether `$carroadnameverify2` is null in the `elsif` statement? If so, I think you meant this: `... elsif ($carroadnameverify2 eq '') { ...` [download] `$carroadnameverify2 =~ ''` will evaluate to true, regardless of `$carroadnameverify2`'s value or whether it's even defined.	[reply] [d/l] [select]
Re^2: Output Repeats in the elsif statement by PilotinControl (Pilgrim) on Feb 13, 2013 at 21:19 UTC
changing it to "eq" causes the output to be blank not returning the Car Record Not Found...leaving it at =~ causes the Car Record Not Found to be repeated over and over for three lines of output...thats the problem	[reply]
Re^3: Output Repeats in the elsif statement by Kenosis (Priest) on Feb 13, 2013 at 22:04 UTC
Ah! Just use `else`: `else { printf("CAR RECORD NOT FOUND"); }` [download] As your `if` tests for the record...	[reply] [d/l] [select]
Re^4: Output Repeats in the elsif statement by PilotinControl (Pilgrim) on Feb 14, 2013 at 02:28 UTC
Re^5: Output Repeats in the elsif statement by Athanasius (Archbishop) on Feb 14, 2013 at 03:12 UTC
Re^5: Output Repeats in the elsif statement by Kenosis (Priest) on Feb 14, 2013 at 03:13 UTC
Re: Output Repeats in the elsif statement by nvivek (Vicar) on Feb 14, 2013 at 05:23 UTC
If you want to check $carroadnameverify2 as empty, you can try following. `elsif(!defined $carroadnameverify2 && $carroadnameverify2 =~ /^\s*$/)` [download] Above condition will print CAR RECORD NOT FOUND message when $carroadnameverify2 is undef or null or string with blank characters.	[reply] [d/l]
Re^2: Output Repeats in the elsif statement by PilotinControl (Pilgrim) on Feb 14, 2013 at 12:45 UTC
Thank you perl monks! The solutions given worked! Much appreciated. Thanks again!	[reply]


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