FAQ
Dear List
I have write the The following code to check a file and print only distinct
lines to a new file and skips the duplicate lines. My source file is as
follows

hello how are you?
hello how are you?
What language did you want to use?
What language did you want to use?
I am here
You are there
this is my first perl script
What language did you want to use?

###############################################################################
my code is as follows


#use strict;
#use warnings;

print "Enter the Absolutepath of the file\t";
my $input=<STDIN>;
chomp($input);

dup($input);

sub dup
{
my $filename=shift;
my $count=0;
my @arr;
my $el;
my $element;
open(FH,"$filename");
while(<FH>)
{
chomp($_);
$element = $_;
if($count ==0)
{
push(@arr,$element);
$count+=1;
print "Count is $count\n";
}
else
{
foreach $el(@arr)
{
my $len=$#arr;
chomp($el);
# print "$element\n";
#print "The length of arr is $len\n";
if($el == $element)
{
print "\t######Inside If######\t\n";
print $element."\n";
next;
#push(@arr,$_);
}

elsif($el != $element)
{
push(@arr,$element);
print "\t########Inside Elseif\n";
#next;
}
}
}
}

###############################################################
The problems I am facing are

1) The code is not getting entered into elsif block

2) I am comparing between 2 strings but if I use "eq" or "ne" for
comparison I am getting some horrible output so I am using numeric
comparison.

3)If I am giving print the $element variable outside foreach loop it is
getting printed but Inside foreach loop it is not showing anything.

Can anybody Please suggest me where I am making the mistake?

Thanks & Regards in Advance
Anirban Adhikary.

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  • Xavier Mas at Aug 25, 2008 at 10:29 am

    El Monday 25 August 2008 11:30:19 Anirban Adhikary va escriure:
    Dear List
    I have write the The following code to check a file and print only distinct
    lines to a new file and skips the duplicate lines. My source file is as
    follows

    hello how are you?
    hello how are you?
    What language did you want to use?
    What language did you want to use?
    I am here
    You are there
    this is my first perl script
    What language did you want to use?

    ###########################################################################
    #### my code is as follows


    #use strict;
    #use warnings;

    print "Enter the Absolutepath of the file\t";
    my $input=<STDIN>;
    chomp($input);

    dup($input);

    sub dup
    {
    my $filename=shift;
    my $count=0;
    my @arr;
    my $el;
    my $element;
    open(FH,"$filename");
    while(<FH>)
    {
    chomp($_);
    $element = $_;
    if($count ==0)
    {
    push(@arr,$element);
    $count+=1;
    print "Count is $count\n";
    }
    else
    {
    foreach $el(@arr)
    {
    my $len=$#arr;
    chomp($el);
    # print "$element\n";
    #print "The length of arr is $len\n";
    if($el == $element)
    {
    print "\t######Inside If######\t\n";
    print $element."\n";
    next;
    #push(@arr,$_);
    }

    elsif($el != $element)
    {
    push(@arr,$element);
    print "\t########Inside Elseif\n";
    #next;
    }
    }
    }
    }

    ###############################################################
    The problems I am facing are

    1) The code is not getting entered into elsif block

    2) I am comparing between 2 strings but if I use "eq" or "ne" for
    comparison I am getting some horrible output so I am using numeric
    comparison.

    3)If I am giving print the $element variable outside foreach loop it is
    getting printed but Inside foreach loop it is not showing anything.

    Can anybody Please suggest me where I am making the mistake?

    Thanks & Regards in Advance
    Anirban Adhikary.
    Did you try to use uniq comand from the Unix bash? I think code would be much
    easy (use exe or sytem to call the command).

    Otherwise, $count always equals to zero when going into dup subroutine.

    --
    Xavier Mas


    ______________________________________________
    LLama Gratis a cualquier PC del Mundo.
    Llamadas a fijos y m�viles desde 1 c�ntimo por minuto.
    http://es.voice.yahoo.com
  • Rob Dixon at Aug 25, 2008 at 11:09 am

    Anirban Adhikary wrote:
    Dear List
    I have write the The following code to check a file and print only distinct
    lines to a new file and skips the duplicate lines. My source file is as
    follows

    hello how are you?
    hello how are you?
    What language did you want to use?
    What language did you want to use?
    I am here
    You are there
    this is my first perl script
    What language did you want to use?

    ###############################################################################
    my code is as follows


    #use strict;
    #use warnings;
    Never comment out these lines - they help enormously to find simple errors.
    print "Enter the Absolutepath of the file\t";
    my $input=<STDIN>;
    chomp($input);

    dup($input);

    sub dup
    {
    my $filename=shift;
    my $count=0;
    my @arr;
    my $el;
    my $element;
    - Variables should be declared as close as possible to their point of first use.

    - Try to use meaningful variable names; the @ in @arr means 'array' so you have
    something called "array arr". Also the difference between the function of $el
    and $element isn't clear from their names.
    open(FH,"$filename");
    while(<FH>)
    - You must always check whether a file open succeeded.

    - $filename should stand on its own. Read the perlfaq article

    perldoc -q quoting

    entitled What's wrong with always quoting "$vars"?

    - The three-parameter form of open and lexical file handles are preferred, like this

    open my $fh, '<', $filename or die $!;
    while (<$fh>) {
    {
    chomp($_);
    $element = $_;
    if($count ==0)
    {
    push(@arr,$element);
    $count+=1;
    print "Count is $count\n";
    $count isn't a count, as it is only incremented when it is zero and never used
    thereafter. You also don't need it at all, so you can remove this if statement
    altogether.
    }
    else
    {
    foreach $el(@arr)
    {
    my $len=$#arr;
    $len is the index of the last element of @arr, not its length. Use

    my $len = @arr;

    to get that.
    chomp($el);
    The strings were chomped before they were added to @arr so there is no need to
    do it again.
    # print "$element\n";
    #print "The length of arr is $len\n";
    if($el == $element)
    The == operator is for comparing numbers; to compare strings you must use
    eq. This is why your elsif block wasn't being executed: the values are being
    forced to numbers before they are compared, and since non-numeric strings
    evaluate as zero they were always numerically equal.

    If you had left warnings enabled you would have a message to tell you this.
    {
    print "\t######Inside If######\t\n";
    print $element."\n";
    next;
    #push(@arr,$_);
    }

    elsif($el != $element)

    There is no need to test again. If

    $el eq $element

    failed, then

    $el ne $element

    must succeed, and you need only an 'else' here.
    {
    push(@arr,$element);
    You shouldn't modify an array that you're currently iterating over, as the
    results aren't guaranteed and anything may happen. In other words, don't write

    foreach (@arr) {
    :
    push @arr, $val;
    :
    }
    print "\t########Inside Elseif\n";
    #next;
    }
    }
    }
    - The braces aren't paired properly in your program. I presume an extra one
    belongs here.

    - You test each new line again /every/ element in @arr, and push the line onto
    the array /every time/ it finds an array element that doesn't match. I assume
    you want to push the new line onto the array only if none of the elements match?
    Something like this perhaps

    while (my $element = <$fh>) {

    chomp $element;

    my $found;

    foreach my $el(@arr) {
    if ($el eq $element) {
    $found++;
    last;
    }
    }

    if (not $found) {
    print "$element\n";
    push @arr,$element;
    }
    }
    }

    ###############################################################
    The problems I am facing are

    1) The code is not getting entered into elsif block

    2) I am comparing between 2 strings but if I use "eq" or "ne" for
    comparison I am getting some horrible output so I am using numeric
    comparison.

    3)If I am giving print the $element variable outside foreach loop it is
    getting printed but Inside foreach loop it is not showing anything.

    Can anybody Please suggest me where I am making the mistake?
    HTH,

    Rob
  • John W. Krahn at Aug 25, 2008 at 12:04 pm

    Anirban Adhikary wrote:
    Dear List
    I have write the The following code to check a file and print only distinct
    lines to a new file and skips the duplicate lines. My source file is as
    follows

    hello how are you?
    hello how are you?
    What language did you want to use?
    What language did you want to use?
    I am here
    You are there
    this is my first perl script
    What language did you want to use?

    ###############################################################################
    my code is as follows


    #use strict;
    #use warnings;

    print "Enter the Absolutepath of the file\t";
    my $input=<STDIN>;
    chomp($input);

    dup($input);

    sub dup
    {
    my $filename=shift;
    my $count=0;
    my @arr;
    my $el;
    my $element;
    open(FH,"$filename");
    while(<FH>)
    {
    chomp($_);
    $element = $_;
    if($count ==0)
    {
    push(@arr,$element);
    $count+=1;
    print "Count is $count\n";
    }
    else
    {
    foreach $el(@arr)
    {
    my $len=$#arr;
    chomp($el);
    # print "$element\n";
    #print "The length of arr is $len\n";
    if($el == $element)
    {
    print "\t######Inside If######\t\n";
    print $element."\n";
    next;
    #push(@arr,$_);
    }

    elsif($el != $element)
    {
    push(@arr,$element);
    print "\t########Inside Elseif\n";
    #next;
    }
    }
    }
    }

    ###############################################################
    The problems I am facing are

    1) The code is not getting entered into elsif block

    2) I am comparing between 2 strings but if I use "eq" or "ne" for
    comparison I am getting some horrible output so I am using numeric
    comparison.

    3)If I am giving print the $element variable outside foreach loop it is
    getting printed but Inside foreach loop it is not showing anything.

    Can anybody Please suggest me where I am making the mistake?
    The usual way to do what you want is to use a hash:

    use strict;
    use warnings;

    print "Enter the Absolutepath of the file\t";
    chomp( my $filename = <STDIN> );

    open my $FH, '<', $filename or die "Cannot open '$filename' $!";

    my %seen;
    while ( <$FH> ) {
    unless ( $seen{ $_ }++ ) {
    print;
    }
    }

    __END__




    John
    --
    Perl isn't a toolbox, but a small machine shop where you
    can special-order certain sorts of tools at low cost and
    in short order. -- Larry Wall
  • Anirban Adhikary at Aug 25, 2008 at 12:37 pm
    Thanks a lot John . I have a little question can u please dexcribe in detail
    what this line is doing actually
    unless ( $seen{ $_ }++ )

    Thanks & regards in advance
    Anirban Adhikary
    On Mon, Aug 25, 2008 at 5:34 PM, John W. Krahn wrote:

    Anirban Adhikary wrote:
    Dear List
    I have write the The following code to check a file and print only
    distinct
    lines to a new file and skips the duplicate lines. My source file is as
    follows

    hello how are you?
    hello how are you?
    What language did you want to use?
    What language did you want to use?
    I am here
    You are there
    this is my first perl script
    What language did you want to use?


    ###############################################################################
    my code is as follows


    #use strict;
    #use warnings;

    print "Enter the Absolutepath of the file\t";
    my $input=<STDIN>;
    chomp($input);

    dup($input);

    sub dup
    {
    my $filename=shift;
    my $count=0;
    my @arr;
    my $el;
    my $element;
    open(FH,"$filename");
    while(<FH>)
    {
    chomp($_);
    $element = $_;
    if($count ==0)
    {
    push(@arr,$element);
    $count+=1;
    print "Count is $count\n";
    }
    else
    {
    foreach $el(@arr)
    {
    my $len=$#arr;
    chomp($el);
    # print "$element\n";
    #print "The length of arr is $len\n";
    if($el == $element)
    {
    print "\t######Inside If######\t\n";
    print $element."\n";
    next;
    #push(@arr,$_);
    }

    elsif($el != $element)
    {
    push(@arr,$element);
    print "\t########Inside Elseif\n";
    #next;
    }
    }
    }
    }

    ###############################################################
    The problems I am facing are

    1) The code is not getting entered into elsif block

    2) I am comparing between 2 strings but if I use "eq" or "ne" for
    comparison I am getting some horrible output so I am using numeric
    comparison.

    3)If I am giving print the $element variable outside foreach loop it is
    getting printed but Inside foreach loop it is not showing anything.

    Can anybody Please suggest me where I am making the mistake?
    The usual way to do what you want is to use a hash:

    use strict;
    use warnings;

    print "Enter the Absolutepath of the file\t";
    chomp( my $filename = <STDIN> );

    open my $FH, '<', $filename or die "Cannot open '$filename' $!";

    my %seen;
    while ( <$FH> ) {
    unless ( $seen{ $_ }++ ) {
    print;
    }
    }

    __END__




    John
    --
    Perl isn't a toolbox, but a small machine shop where you
    can special-order certain sorts of tools at low cost and
    in short order. -- Larry Wall


    --
    To unsubscribe, e-mail: beginners-unsubscribe@perl.org
    For additional commands, e-mail: beginners-help@perl.org
    http://learn.perl.org/

  • John W. Krahn at Aug 25, 2008 at 1:17 pm

    Anirban Adhikary wrote:
    On Mon, Aug 25, 2008 at 5:34 PM, John W. Krahn wrote:

    The usual way to do what you want is to use a hash:

    use strict;
    use warnings;

    print "Enter the Absolutepath of the file\t";
    chomp( my $filename = <STDIN> );

    open my $FH, '<', $filename or die "Cannot open '$filename' $!";

    my %seen;
    while ( <$FH> ) {
    unless ( $seen{ $_ }++ ) {
    print;
    }
    }

    __END__
    Thanks a lot John . I have a little question can u please dexcribe in detail
    what this line is doing actually
    unless ( $seen{ $_ }++ )
    $_ contains the current line from the file. ++ is the postfix
    auto-increment operator. The hash %seen contains the line from the file
    as the key and the number of times the line was "seen" as the value.
    The value of $seen{$_} is tested to see if it is true or false and after
    it is tested the value is incremented so if a line is not already in the
    hash the value will be false (undef) and that line will be printed.



    John
    --
    Perl isn't a toolbox, but a small machine shop where you
    can special-order certain sorts of tools at low cost and
    in short order. -- Larry Wall

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groupbeginners @
categoriesperl
postedAug 25, '08 at 9:30a
activeAug 25, '08 at 1:17p
posts6
users4
websiteperl.org

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