Perl Guru Forums: Perl Programming Help: Beginner: Print Hash Keys

CGI/Perl Guide | Learning Center | Forums | Advertise | Login

Site Search: in


	MAIN INDEX	SEARCH POSTS	WHO'S ONLINE	LOG IN

Home: Perl Programming Help: Beginner:
Print Hash Keys

Stefanik
User

Jan 3, 2013, 12:50 AM

Post #1 of 10 (1011 views)

Print Hash Keys	Can't Post

Hi all, I've should print out the hash keys to a file, separated with newline:

Code

my $KeyHa = $value1; 
my $ValHA = 1; 
$Ha_ha{$KeyHa} = $ValHA;  
 
open (PARSEOUTFILE, ">", $FileParsed) or die "No file!"; 
@Ha_KeyArr = keys %Ha_ha; 
print PARSEOUTFILE "@Ha_KeyArr\n";

In output file I have the key printed with a space " " at the begin:

" key1 key2"

While I'd like to have:

"key1

key2"

Can you help me?

Laurent_R
Enthusiast

Jan 3, 2013, 4:43 AM

Post #2 of 10 (1008 views)

Re: [Stefanik] Print Hash Keys [In reply to]	Can't Post

Hi,

one way to do it:

Code

# ... 
$Ha_KeyScalar = join "\n", keys %Ha_ha; 
print PARSEOUTFILE "$Ha_KeyScalar";

FishMonger
Veteran

Jan 3, 2013, 6:47 AM

Post #3 of 10 (1003 views)

Re: [Stefanik] Print Hash Keys [In reply to]	Can't Post

Here are 3 methods. There are more ways to do it, but my preference is the second one, however, I'd use a lexical filehandle instead of the bareword.

Code

print PARSEOUTFILE "$_\n" for keys %Ha_ha;

Code

# if using perl 5.10.0 or above 
say PARSEOUTFILE $_ for keys %Ha_ha;

Code

my @keys = keys %Ha_ha; 
$" = "\n"; 
print "@keys";

Stefanik
User

Jan 3, 2013, 6:59 AM

Post #4 of 10 (1001 views)

Re: [FishMonger] Print Hash Keys [In reply to]	Can't Post

Thanks to all of you Smile

Is it possible to have an hash key with character empty (" " or "") ?

In that case to erase it, should I use a loop:

Code

  if (($value1 != " ") && ($value1 != ""))  
{  
my $KeyHa = $value1;  
my $ValHA = 1;  
$Ha_ha{$KeyHa} = $ValHA;  
}

Or is it possible to execute the check while I assign the variable to the Hash-key?

(This post was edited by Stefanik on Jan 3, 2013, 7:08 AM)

FishMonger
Veteran

Jan 3, 2013, 7:47 AM

Post #5 of 10 (996 views)

Re: [Stefanik] Print Hash Keys [In reply to]	Can't Post

It would be best to validate your data prior to adding it to the hash, but if that wasn't done, then you can use the delete function to remove the unwanted key/value pair from the hash.

Stefanik
User

Jan 3, 2013, 1:29 PM

Post #6 of 10 (986 views)

Re: [FishMonger] Print Hash Keys [In reply to]	Can't Post

Ok I find out the "empty" lines are the ones does not match the condition.
So I try, as suggest to delete at the begin:

Code

open (PARSEFILE, "<", $FileToParse) or die "No file!"; 
while ($FirstPar = <PARSEFILE>){ 
	@Parse_Arr = $FirstPar unless ( $FirstPar =~ m/Mystring1|Mystring2/ ); 
	print @Parse_Arr; 
} 
close (PARSEFILE);

In this case the lines in the file that match Mystring1 or Mystring2 doesn't print in array, instead are duplicated the previous line. Unimpressed

Why?

7stud
Enthusiast

Jan 3, 2013, 1:50 PM

Post #7 of 10 (984 views)

Re: [Stefanik] Print Hash Keys [In reply to]	Can't Post

...because you only assign a new value to @Parse_Arr when there is no match, yet you print every time through the loop. So if there is a match, you don't assign a new value to @Parse_Arr, and so @ParseArr has the old value, i.e. from the previous line, which you then print.

You want something like this:

Code

 
 
next if $FirstPar =~ /Mystring1|Mystring2/ ; 
 
print @Parse_Arr;

That way the print statement is skipped if there is a match.

By the way, your variable names are terrible. See how much clearer this code is:

Code

use strict;  
use warnings;  
use 5.012; 
 
my $fname = 'data.txt'; 
 
open my $INFILE, "<", $fname 
  or die "Couldn't open $fname: $!"; 
 
while (my $line = <$INFILE>){ 
    next if $line =~ /string1|string2/; 
    print $line; 
} 
 
close $INFILE;

Generally, you don't capitalize your variable names. Some people capitalize variable names that contain references to file handles, so that they look similar to bareword filehandles(which you shouldn't be using).

(This post was edited by 7stud on Jan 3, 2013, 2:11 PM)

Stefanik
User

Jan 3, 2013, 2:39 PM

Post #8 of 10 (966 views)

Re: [7stud] Print Hash Keys [In reply to]	Can't Post

Thanks 7stud for the information and suggest.

Just one think it's not clear for me: to assign the value in "while" loop to Array, should I increment Array index, or is it performed automatically?

Thanks

FishMonger
Veteran

Jan 3, 2013, 2:48 PM

Post #9 of 10 (964 views)

Re: [Stefanik] Print Hash Keys [In reply to]	Can't Post

You use the push function to add item onto an array.

http://perldoc.perl.org/functions/push.html

Stefanik
User

Jan 4, 2013, 12:16 AM

Post #10 of 10 (956 views)

Re: [FishMonger] Print Hash Keys [In reply to]	Can't Post

Thanks again.

Search for (options)

Web Applications & Managed Hosting Powered by Gossamer Threads
Visit our Mailing List Archives