I have written a code to get the url of a website and then search for a string and then compare that string(actually a number) with a hardcoded number
#!/usr/bin/perl
use LWP::Simple;
my $oldversion =36;
$pageURL="http://www.google.com/isos/preFCS5.3/LATESTGOODCVP/";
my $simplePage=get($pageURL);
my $newPage = "$simplePage";
my $str = (split("href=\"CVP-LATEST-5.3.0.",$newPage ))[1];
my $version = substr("$str",0,2);
print $version; // HERE IT PRINT 37 WHICH IS CORRECT
if($version =! $oldVersion )
{
print $version; // BUT HERE IT PRINTS 1 WHICH IS WRONG. HOW IS IT CHANGING ?
##-- fetch the zip and save it as perlhowto.zip
my $status = getstore("http://www.google.com/isos/preFCS5.3/LATESTGOODCVP/CVP-LATEST-5.3.0.$version.iso", "CVP-LATEST-5.3.0.$version.iso");
}
else
{
print("Currently new version\n");
}
Why is it changing the value ? its not able to download the file becuase of that.
You mean !=, not =!, which is an assignment of a negation.
Also, split always uses a regex (except for the very special case of a string that has a single space), so those .s in 5.3.0. will match any non-newline. You probably want to \-escape them.
You may be interested in the uscan script in the debian devtools package.
You have got your "not equals" operator backwards. It should be != rather than =!.
By using =! you are in effect saying "set $version to the negated value of $oldversion".
Here is the offending line
if($version =! $oldVersion ) # Should be if($version != $oldVersion )
Also notice that by using the != operator you are telling perl that $version and $oldversion contain numbers. For string comparisons you should use the ne operator, which assumes that these variables contain strings.
if($version ne $oldVersion ) # String inequality
Here is the documentation for equality operators -
http://perldoc.perl.org/perlop.html#Equality-Operators
It's because you are assigning to $version the value !$oldVersion in this "test":
if($version =! $oldVersion )
And $oldVersion is nothing--but $oldversion is 37. You are assigning $version the boolean negation of an undefined variable. Undefined is boolean false, and so the negation is boolean true or 1.
If you read very much on perl, you're bound to come across the advice to use strict and warnings. Had you done that, it would have told you, among other things:
Global symbol "$oldVersion" requires explicit package name at - line 21.
This means that you didn't declare $oldVersion as lexical (my) or package-level (our) in this package, so if you want to use it, please include the package where you're getting it. In a vast majority of cases, a seasoned Perl programmer will recognize this as "Ugh, I didn't declare $oldVersion!" and the reason is that you declared $oldversion.
Your use of split doesn't make a lot of sense here. What you really want are the two digits following the CVP-LATEST-5.3.0. string. You're also not really doing anything by assigning one variable to another with the addition of quotes ($newPage = "$simplePage").
And, of course, as others have pointed out, the comparison is != not =!.
I'd rewrite this as:
use strict;
use warnings;
use LWP::Simple;
my $oldVersion = 36;
my $url = 'http://www.google.com/isos/preFCS5.3/LATESTGOODCVP/';
my $newPage = get($url)
or die "Cannot retrieve contents from $url\n";
if ( $newPage =~ /href=\"CVP-LATEST-5\.3\.0\.(\d\d)/ ) {
my $version = $1;
if ( $version != $oldVersion ) {
my $status = getstore($url . "CVP-LATEST-5.3.0.$version.iso",
"CVP-LATEST-5.3.0.$version.iso");
} else {
print "Already at most recent version\n";
}
} else {
die "Cannot find version tag in contents from $url\n";
}
Related
my $line ="Corner:Default,Output:fall_delay_slew_1,Mean=34.97p,Std- dev=1.767p,Min=30.02p,Max=39.71p"; #added semicolon
my $my_value="COND = Mean > 3"; #this has come from the parsed file.
$my_value =~ m/(\w+)\s*(.)\s*(\d+)/;
my $cond=$1;
my $sign=$2;
my $value=$3;
print "DEBUG:cond is $cond and sign $sign and value $value \n";
if ( $line =~ m/$cond=(.*?),/) {
if ( "$value $sign $1" ) {
print "$value is $sign than $1\n";
} else {
print "actual value is less\n";
}
}
If you see in the above if statement always evaluates to true.
How can I solve this kind of problem i.e $sign = "<" (could be any operator)
but when I want to compare it with $value I want it to function as an
operator and not as a string.
What you're willing to do (executing a string as code) can be done with
eval. That doesn't mean it is the most appropriate way of doing
it though. Do it only if you guarantee your input safety and check for
it.
A better way would be checking the operator your self and determining
how to proceed. If you use a recent Perl version, the given-when
feature can be handy to do this:
use feature 'switch'; # not needed if you already use 5.010 or greater
given ($sign) {
when ('<') { say "$cond less than $value" }
when ('>') { say "$cond greater than $value" }
default {
warn "unrecognized operator `$sign'\n";
# decide what to do
}
}
I'm trying to parse a CSV file that is formatted like this:
dog cats,yellow blue tomorrow,12445
birds,window bank door,-novalue-
birds,window door,5553
aspirin man,red,567
(there is no value where -novalue- is written)
use strict;
use warnings;
my $filename = 'in.txt';
my $filename2 = 'out.txt';
open(my $in, '<:encoding(UTF-8)', $filename)
or die "Could not open file '$filename' $!";
my $word = "";
while (my $row = <$in>) {
chomp $row;
my #fields = split(/,/,$row);
#Save the first word of the second column
($word) = split(/\s/,$fields[1]);
if ($word eq 'importartWord')
{
printf $out "$fields[0]".';'."$word".';'."$fields[2]";
}
else #keep as it was
{
printf $out "$fields[0]".';'."$fields[1]".';'."$fields[2]";
}
Use of uninitialized value $word in string ne at prueba7.pl line 22, <$in> line 10.
No matter where I define $word I cannot stop receiving that error and can't understand why. I think I have initialized $word correctly. I would really appreciate your help here.
Please if you are going to suggest using Text::CSV post a working code example since I haven't been able to apply it for the propose I have explained here. That's the reason I ended up writing the above code.
PD:
Because I know you are going to ask for my previous code using Text::CSV, here it is:
#!/usr/bin/perl
use strict;
use warnings;
use Text::CSV;
my $csv = Text::CSV->new({ sep_char => ';', binary => 1 }) or
die "Cannot use CSV: ".Text::CSV->error_diag ();
#directorio donde esta esc_prim2.csv
my $file = 'C:\Users\Sergio\Desktop\GIS\perl\esc_prim2.csv';
my $sal = 'C:\Users\Sergio\Desktop\GIS\perl\esc_prim3.csv';
open my $data, "<:encoding(utf8)", "$file" or die "$file: $!";
open my $out, ">:encoding(utf8)", "$sal" or die "$sal: $!";
$csv->eol ("\r\n");
#initializing variables
my $row = "";
my $word = "";
my $validar = 0;
my $line1 = "";
my #mwords = [""];#Just a try to initialize mwords... doesn't work, error keeps showing
#save the first line with field names on the other file
$line1 = <$data>;
$csv->parse($line1);
my #fields = $csv->fields();
$csv->print($out,[$fields[0], $fields[1], $fields[2]]);
while ($row = <$data>) {
if ($csv->parse($row)) {
#fields = $csv->fields();
#save first word of the field's second element
#mwords = split (/\s/, $fields[1]);
#keep the first one
$word = $mwords[0];
printf($mwords[0]);
#if that word is not one of SAN, EL y LA... writes a line in the new file with the updated second field.
$validar = ($word ne 'SAN') && ($word ne 'EL') && ($word ne 'LA');
if ($validar)
{
$csv->print($out,[$fields[0], $word, $fields[2]]);
}
else { #Saves the line in the new file as it was in the old one.
$csv->print($out,[$fields[0], $fields[1], $fields[2]]);
}
} else {#error procesing row
warn "La row no se ha podido procesar\n";
}
}
close $data or die "$file: $!";
close $out or die "$sal: $!";
Here the line where $validar is declared brings the same error of "uninitialized value" although I did it.
I also tried the push #rows, $row; approach but I don't really know how to handle the $rows[$i] since they are references to arrays (pointers) and I know they can't be operated as variables... Couldn't find a working example on how to use them.
I think you're misunderstanding the error. It's not a problem with the declaration of the variable, but with the data that you're putting into the variable.
Use of uninitialized value
This means that you are trying to use a value that is undefined (not undeclared). That means you are using a variable that you haven't given a value.
You can get more details about the warning (and it's a warning, not an error) by adding use diagnostics to your code. You'll get something like this:
(W uninitialized) An undefined value was used as if it were already
defined. It was interpreted as a "" or a 0, but maybe it was a mistake.
To suppress this warning assign a defined value to your variables.
To help you figure out what was undefined, perl will try to tell you
the name of the variable (if any) that was undefined. In some cases
it cannot do this, so it also tells you what operation you used the
undefined value in. Note, however, that perl optimizes your program
and the operation displayed in the warning may not necessarily appear
literally in your program. For example, "that $foo" is usually
optimized into "that " . $foo, and the warning will refer to the
concatenation (.) operator, even though there is no . in
your program.
So, when you're populating $word, it's not getting a value. Presumably, that's because some lines in your input file have an empty record there.
I have no way of knowing whether or not that's a valid input for your program, so I can't really give any helpful suggestions on how to fix this.
The error message you provided ends with: line 22, <$in> line 10. but your question doesn't show line 10 of the data ($in) requiring some speculation in this answer - but, I'd say that the second field, $field[1], of line 10 of in.txt is empty.
Consequently, this line: ($word) = split(/\s/,$fields[1]); is causing $word to be undefined. As a result, some use of it latter - be it the ne operator (as displayed in the message) or anything else is going to generate an error.
As an aside - there's little point in interpolating a variable in a string on its own; instead of "$fields[0]", say $fields[0] unless you're going to put something else in there, like "$fields[0];". You may want to consider replacing
printf $out "$fields[0]".';'."$word".';'."$fields[2]";
with
printf $out $fields[0] . ';' . $word . ';' . $fields[2];
or
printf $out "$fields[0];$word;$fields[2]";
Of course, TMTOWTDI - so you may want to tell me to mind my own business instead. :-)
my $line = "hello";
print ($line == undef);
The check should be false since $line is not undefined (I defined it in the first line). Why is this code snippet printing out '1'?
It's doing exactly what you said.
print ($line == undef);
You're printing out a boolean value because ($line == undef) is a boolean statement.
The == is a numeric equals. Since $line is text, it has the value of 0. So does undef numerically. Thus ($line == undef) is true.
You should always put the following on the top of your program:
use strict;
use warnings;
There are other pragmas people put, but these are the two most important. They will find 90% of your errors. Try this program:
use strict;
use warnings;
my $line = "hello";
print ($line == undef)
You'll get:
Use of uninitialized value in numeric eq (==) at ./test.pl line 6.
Argument "hello" isn't numeric in numeric eq (==) at ./test.pl line 6.
Of course I have an uninitialized value! I'm using undef. And, of course hello isn't a numeric value.
I'm not entirely sure what you want. Do you want to print out hello if it's not defined? Are you trying to see the value of that boolean statement?
What about that \n on the end that print doesn't put on the end of the line? Do you want that? Because print can be prone to the forgotten \n error, I prefer to use say:
use strict;
use warnings;
use feature qw(say); # Say is like print but includes the ending `\n`
my $line = "hello";
say (not defined $line); # Will print null (false) because the line is defined
say ( defined $line); # Will print "1" (true).
say ( $line ne undef); # Will print '1' (true), but will give you a warning.
say $line if defined line; # Will print out $line if $line is defined
Always put
use strict; use warnings;
or
use Modern::Perl;
you will see some errors :
Use of uninitialized value in numeric eq (==) at /tmp/sssl.pl line 3.
Argument "hello" isn't numeric in numeric eq (==) at /tmp/sssl.pl line 3.
To test if a variable is defined, use :
print "variable defined" if defined $variable;
To test a string against another string, use :
if ($string eq $another_string) { ... }
In my perl script I want to have both versions of $config directory:
my $config='$home/client/config';
and
my $config_resolved="$home/client/config";
But I want to get $config_resolved from $config, i.e. something like this:
my $config_resolved=resolve_vars($config);
How can I do such thing in perl?
From the Perl FAQ (which every Perl programmer should read at least once):
How can I expand variables in text strings?
(contributed by brian d foy)
If you can avoid it, don't, or if you can
use a templating system, such as Text::Template or Template Toolkit,
do that instead. You might even be able to get the job done with
sprintf or printf:
my $string = sprintf 'Say hello to %s and %s', $foo, $bar;
However, for the one-off simple case where I don't want to pull out a
full templating system, I'll use a string that has two Perl scalar
variables in it. In this example, I want to expand $foo and $bar to
their variable's values:
my $foo = 'Fred';
my $bar = 'Barney';
$string = 'Say hello to $foo and $bar';
One way I can do this involves the substitution operator and a double /e flag. The
first /e evaluates $1 on the replacement side and turns it into $foo. The
second /e starts with $foo and replaces it with its value. $foo,
then, turns into 'Fred', and that's finally what's left in the string:
$string =~ s/(\$\w+)/$1/eeg; # 'Say hello to Fred and Barney'
The /e will also silently ignore violations of strict, replacing undefined
variable names with the empty string. Since I'm using the /e flag
(twice even!), I have all of the same security problems I have with
eval in its string form. If there's something odd in $foo, perhaps
something like #{[ system "rm -rf /" ]}, then I could get myself in
trouble.
To get around the security problem, I could also pull the
values from a hash instead of evaluating variable names. Using a
single /e, I can check the hash to ensure the value exists, and if it
doesn't, I can replace the missing value with a marker, in this case
??? to signal that I missed something:
my $string = 'This has $foo and $bar';
my %Replacements = (
foo => 'Fred',
);
# $string =~ s/\$(\w+)/$Replacements{$1}/g;
$string =~ s/\$(\w+)/
exists $Replacements{$1} ? $Replacements{$1} : '???'
/eg;
print $string;
I use eval for this.
So, you must replace all scalars (their names) with their values.
$config = 'stringone';
$boo = '$config/any/string';
$boo =~ s/(\$\w+)/eval($1)/eg;
print $boo;
Because you are using my to declare it as private variable, you might as well use a /ee modifier. This can find variables declared to be in local scope:
$boo =~ s/(\$\w+)/$1/eeg;
This is most tidily and safely done by the double-eval modifier on s///.
In the program below, the first /e evaluates the string $1 to get $home, while the second evaluates $home to get the variable's value HOME.
use strict;
my $home = 'HOME';
my $config = '$home/client/config';
my $config_resolved = resolve_vars($config);
print $config_resolved, "\n";
sub resolve_vars {
(my $str = shift) =~ s/(\$\w+)/$1/eeg;
return $str;
}
output
HOME/client/config
I've tried searching through questions already asked, but can't seem to find anything. I'm sure its incredibly simple to do, but I am completely new to Perl.
What I am trying to do is remove characters in an string up to a certain point. For example, I have:
Parameter1 : 0xFFFF
and what I would like to do is remove the "Parameter1:" and be left with just the "0xFFFF". If anyone can help and give a simple explanation of the operators used, that'd be great.
Sounds like you need the substr function.
#!/usr/bin/perl
use strict;
use warnings;
my $string = 'Parameter1 : 0xFFFF';
my $fragment = substr $string, 12;
print " string: <$string>\n";
print "fragment: <$fragment>\n";
s/.*:\s*//;
or
$s =~ s/.*:\s*//;
This deletes everything up to and including the first occurrence of : followed by zero or more whitespace characters. With $s =~ it's applied to $s; without it, it's applied to $_.
Have you considered using something like Config::Std?
Here is how to parse a configuration file like that by hand:
#!/usr/bin/perl
use strict; use warnings;
my %params;
while ( my $line = <DATA> ) {
if ($line =~ m{
^
(?<param> Parameter[0-9]+)
\s*? : \s*?
(?<value> 0x[[:xdigit:]]+)
}x ) {
$params{ $+{param} } = $+{value};
}
}
use YAML;
print Dump \%params;
__DATA__
Parameter1 : 0xFFFF
Parameter3 : 0xFAFF
Parameter4 : 0xCAFE
With Config::Std:
#!/usr/bin/perl
use strict; use warnings;
use Config::Std;
my $config = do { local $/; <DATA> };
read_config \$config, my %params;
use YAML;
print Dump \%params;
__DATA__
Parameter1 : 0xFFFF
Parameter3 : 0xFAFF
Parameter4 : 0xCAFE
Of course, in real life, you'd pass a file name to read_config instead of slurping it.
I like split for these parameter/value pairs.
my $str = "Parameter1 : 0xFFFF";
my ($param, $value) = split /\s*:\s*/, $str, 2;
Note the use of LIMIT in the split, which limits the split to two fields (in case of additional colons in the value).