Paul Scheinast @paul-scheinast - Tumblr Blog

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New Post has been published on http://scheinast.eu/perl-find-al-pow-2-numbers/

Perl find al pow 2 numbers

This little script finds all pow 2 numbers in Perl :

use strict; my $number = 0; for(1..32) ++$number; print "$number - ".isPow2($number)."\n"; sub isPow2 return(0) if($_[0] <= 0); return(1) if($_[0] == 1); for(1..6) return(1) if($_[0] == 2**$_) return(0);

Our Result:

1 - 1 2 - 1 3 - 0 4 - 1 5 - 0 6 - 0 7 - 0 8 - 1 9 - 0 10 - 0 11 - 0 12 - 0 13 - 0 14 - 0 15 - 0 16 - 1

#perl

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New Post has been published on http://scheinast.eu/perl-print-string-difference/

Perl print String difference

This function prints the difference between two strings with Perl:

sub printStringDiff my ($s1, $s2) = @_; my @s1 = split(//, $s1); my @s2 = split(//, $s2); while (@s1) if (defined $s1[0] and defined $s2[0]) if($s1[0] eq $s2[0]) print shift @s1; else print color("red"),shift @s1, color("reset"); elsif(defined $s1[0]) print color("red"),shift @s1, color("reset"); shift @s2; print "\n"; @s1 = split(//, $s1); @s2 = split(//, $s2); while (@s2) if (defined $s2[0] and defined $s1[0]) if($s2[0] eq $s1[0]) print shift @s2; else print color("red"),shift @s2, color("reset"); elsif(defined $s2[0]) print color("red"),shift @s2, color("reset"); shift @s1; print "\n";

You need the Module Term::ANSIColor, to highlight the changes,use it like this:

#!/usr/bin/perl use strict; use Term::ANSIColor; printStringDiff("1234","123456"); print "\n"; printStringDiff("123456","1234"); print "\n"; printStringDiff("ABAA","AABA"); print "\n";

And the Result is :

#colour #perl

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New Post has been published on http://scheinast.eu/perl-check-if-file-handler-is-open/

Perl check if file handler is open

If you write a function and want to check if the file handler is already open you could use this function:

sub filehandlerOpen my $fh = shift; no warnings 'uninitialized'; return 0 if(!defined $fh

It returns 0 if its undefined,closed or not open, an 1 if the handler is open.

In this little example I open a file to read and another to write, I check the sub before and after the open function, and before and after the close function.

#!/usr/bin/perl use warnings; use strict; my ($fh_read,$fh_write); print "Check undefined:\n"; print filehandlerOpen($fh_read).$/; print filehandlerOpen($fh_write).$/; open($fh_write, ">", './testfile') or die "Failed to open file: $!\n"; open($fh_read, "<", './testfile') or die "Failed to open file: $!\n"; print "Check defined:\n"; print filehandlerOpen($fh_read).$/; print filehandlerOpen($fh_write).$/; for my $num (1..6) print $fh_write "$num\n"; print "Check close write:\n"; print filehandlerOpen($fh_write).$/; close($fh_write); print filehandlerOpen($fh_write).$/; while (my $row = <$fh_read>) chomp $row; print "Check close read:\n"; print filehandlerOpen($fh_read).$/; close($fh_read); print filehandlerOpen($fh_read).$/; sub filehandlerOpen my $fh = shift; no warnings 'uninitialized'; return 0 if(!defined $fh

The Result, looks like expected:

Check undefined: 0 0 Check defined: 1 1 Check close write: 1 0 Check close read: 1 0

#file handler #perl

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New Post has been published on http://scheinast.eu/perl-print-__data__-multiple-times/

Perl print __DATA__ multiple times

Sometimes you have a lot of Data you want to store in your script, for that you could you the __DATA__ token, you could simple read it with a file handle:

print <DATA>,"\n"; __DATA__ Test String 123456

If you use it more than one time you should seek for the start position:

#!/usr/bin/perl use warnings; use strict; my $data_start = tell DATA; # where __DATA__ begins print <DATA>,"\n"; seek DATA, $data_start, 0; print <DATA>,"\n"; __DATA__ Test String 123456

Output looks like this:

Test String 123456 Test String 123456

#perl

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New Post has been published on http://scheinast.eu/perl-readwrite-file/

Perl read/write File

This is a simple example how to write into a File, and then read from it.At first we write the numbers from 1 to 6 into the file, in the second we read from the file and print it on the screen, if you don’t want the “\n” at the end use the function chomp.

If you open a File for read use ‘<‘, for write ‘>’ and for append ‘>>’.

#!/usr/bin/perl use warnings; use strict; #declare filehandler my ($fh_read,$fh_write); #open file for write open($fh_write, ">", './testfile') or die "Failed to open file: $!\n"; #now write for my $num (1..6) print $fh_write "$num\n"; #close the file close($fh_write); #open file for read open($fh_read, "<", './testfile') or die "Failed to open file: $!\n"; #now read while (my $row = <$fh_read>) print $row; #close the file close($fh_read);

Result looks like:

1 2 3 4 5 6

#example #perl

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New Post has been published on http://scheinast.eu/install-rpm-under-debian/

INSTALL RPM under Debian

If you want to install *.rpm files under Debian you could use alien.

apt-get install alien alien -i package.rpm

#Debian #linux

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New Post has been published on http://scheinast.eu/perl-find-lowest-divisible-number/

Perl find lowest divisible number

This Perl Script find the lowest, divisible number from 1 to 10:

use strict; my ($number,$check) = (0,0); while(1) ++$number; $check=0; for(1..20) unless($number%$_==0)++$check;last; last unless($check); print "$number\n";

The result is 2520.

#perl

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New Post has been published on http://scheinast.eu/fraction-calculation-in-perl/

Fraction calculation in Perl

This Perl script is able to add,subtract,divide and multiply fractional numbers:

use strict; #test data: my @B1 = _read(); my @B2 = _read(); #test addition my @BC = _add(@B1,@B2); print "+:",_print(@BC); # test substract @BC = _sub(@BC,@B2); print "-:",_print(@BC); #simplify the result @BC = simplify(@BC); #test multiplication @BC = _mul(@B1,@B2); print "*:",_print(@BC); #test division @BC = _div(@BC,@B2); print "/:",_print(@BC); #simplify the result @BC = simplify(@BC); sub _add my $gn = $_[1]*$_[3]; return(($_[0]*($gn/$_[1]))+($_[2]*($gn/$_[3])),$gn); sub _sub my $gn = $_[1]*$_[3]; return(($_[0]*($gn/$_[1]))-($_[2]*($gn/$_[3])),$gn); sub _mul return($_[0]*$_[2],$_[1]*$_[3]); sub _div return($_[0]*$_[3],$_[1]*$_[2]); sub _print my @D = &simplify; my $c = 0; while(1) if($D[0]>=$D[1]) $D[0] -= $D[1]; ++$c; else last; if($c) return "$c+$D[0]/$D[1](".&fractial2number.")\n"; else return "$D[0]/$D[1](".&fractial2number.")\n"; sub _read print "fractal number:"; my $in = <STDIN>; if($in =~ /\//o) $in =~ /^(.+)\/(.+)$/o; return($1,$2); else return(number2fractial($in)); sub number2fractial $_[0] =~ /^(.+)\.(.+)$/o; my $d = $1; my $c = $2; my $u = $2; $u =~ s/./0/g; $u = "1".$u; return($c+($d*$u),"$u"); sub fractial2number return($_[0]/$_[1]); sub simplify for($_ = $_[1];$_>=2;--$_) return($_[0]/$_,$_[1]/$_) if($_[0]%$_==0 && $_[1]%$_==0); return($_[0],$_[1]);

This is the output from 1/2 and 1.25, at first add both then subtract from the result, multiply and then divide from the result:

fractal number:1/2 fractal number:1.25 +:1+3/4(1.75) -:1/2(0.5) *:5/8(0.625) /:1/2(0.5)

For a better result take a look at Perl high precision.

#calculator #perl

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New Post has been published on http://scheinast.eu/javascript-generate-an-result-array-from-xpath/

JavaScript generate an result array from XPATH

This is a function in JavaScript that use an XPATH string to generate an Array from the results.This is very useful if you have to manipulate or use some items on a page and don’t have the id(like bots).

That is the function:

function matches2array (XPATH) var links = new Array(); var elements = 0; var xPathRes = document.evaluate (XPATH, document, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null); var actualSpan = xPathRes.iterateNext (); while (actualSpan) links[elements] = actualSpan; actualSpan = xPathRes.iterateNext (); ++elements; return(links);

You could use it in the Terminal:

matches2array("//a");

And we get all hrefs on this page in the Terminal:

[a.skip-link.screen-reader-text #content, a scheinast.eu, a /category/c-sharp/, a /category/c/, a /category/fortran/, a /category/bash/, a /category...-css-js/, a /category/java/, a /category/perl/, a /category/php/, a /category/projects/, a /category/regex/, a /category...-tricks/, a /category/windows/, a /perl-str...nchmark/, a /regex-fi...strings/, a /how-to-o...desktop/, a /c-calculator/, a /javascri...ocation/, a /image-uploader/, a /wp-admin/, a wp-login....68d8990f, a /feed/, a /comments/feed/, a wordpress.org, a.a2a_button_facebook /, a.a2a_button_twitter /, a.a2a_button_google_plus /, a.a2a_dd.addtoany_share_save share_sav...2F%5D..., a /calculator-in-c/, a.url.fn.n /author/p...heinast/, a /category/c/, a /tag/c/, a /tag/calculator/, a.post-edit-link post.php?...ion=edit, a#cancel-comment-reply-link /calculat...#respond, a profile.php, a wp-login....68d8990f, a /new-hompage-design/, a /backtrack-how-to/, a.a2a_button_facebook /, a.a2a_button_twitter /, a.a2a_button_google_plus /, a.a2a_dd.addtoany_share_save share_sav...2F%5D..., a.screen-reader-shortcut #wp-toolbar, a.ab-item about.php, a.ab-item about.php, a.ab-item wordpress.org, a.ab-item codex.wordpress.org, a.ab-item /support/, a.ab-item requests-...feedback, a.ab-item admin.php...tics.php, a.ab-item admin.php...ine_menu, a.ab-item admin.php...tics.php, a.ab-item /wp-admin/, a.ab-item /wp-admin/, a.ab-item themes.php, a.ab-item customize...D=themes, a.ab-item customize...-in-c%2F, a.ab-item widgets.php, a.ab-item customize...=widgets, a.ab-item nav-menus.php, a.ab-item themes.ph...ckground, a.ab-item customize...nd_image, a.ab-item themes.ph...m-header, a.ab-item customize...er_image, a.ab-item edit-comments.php, a.ab-item post-new.php, a.ab-item post-new.php, a.ab-item media-new.php, a.ab-item post-new....ype=page, a.ab-item user-new.php, a.ab-item post.php?...ion=edit, a.ab-item profile.php, a.ab-item profile.php, a.ab-item profile.php, a.ab-item wp-login....68d8990f, a.screen-reader-shortcut wp-login....68d8990f, a.a2a_i.a2a_sss /, a.a2a_i.a2a_sss /, a.a2a_i.a2a_sss /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a, a.a2a_i.a2a_sss /, a.a2a_i.a2a_sss /, a.a2a_i.a2a_sss /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a.a2a_i /, a#a2apage_any_email.a2a_i.a2a_emailer /, a#a2apage_email_client.a2a_i.a2a_emailer.a2a_email_client /, a#a2apage_show_more_less.a2a_menu_show_more_less.a2a_more]

Use it to store it in an Array and then write it on the page:

var scripts = matches2array("//a"); for (i=0;i<scripts.length;i++) document.write(scripts[i] + "\n");

and we got this result:

http://scheinast.eu/calculator-in-c/#content http://scheinast.eu/ http://scheinast.eu/category/c-sharp/ http://scheinast.eu/category/c/ http://scheinast.eu/category/fortran/ http://scheinast.eu/category/bash/ http://scheinast.eu/category/html-css-js/ http://scheinast.eu/category/java/ http://scheinast.eu/category/perl/ http://scheinast.eu/category/php/ http://scheinast.eu/category/projects/ http://scheinast.eu/category/regex/ http://scheinast.eu/category/tips-and-tricks/ http://scheinast.eu/category/windows/ http://scheinast.eu/perl-strict-benchmark/ http://scheinast.eu/regex-find-interpolate-strings/ http://scheinast.eu/how-to-open-remote-desktop/ http://scheinast.eu/c-calculator/ http://scheinast.eu/javascript-location/ http://scheinast.eu/image-uploader/ http://scheinast.eu/wp-admin/ http://scheinast.eu/wp-login.php?action=logout&_wpnonce=a768d8990f http://scheinast.eu/feed/ http://scheinast.eu/comments/feed/ https://wordpress.org/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ https://www.addtoany.com/share_save#url=http%3A%2F%2Fscheinast.eu%2Fcalculator-in-c%2F&title=Calculator%20in%20C%2B%2B&description=This%20is%20my%20calculator%20in%20C%2B%2B%20with%20in-line%20assembler%3A%20%5Bcrayon-556e97ccb93bc417229824%2F%5D%20Compile%20the%20code%3A%20%5Bcrayon-556e97ccb93e1826855153%2F%5D%20output%3A%20%5Bcrayon-556e97ccb93f8566053665%2F%5D... http://scheinast.eu/calculator-in-c/ http://scheinast.eu/author/paul-scheinast/ http://scheinast.eu/category/c/ http://scheinast.eu/tag/c/ http://scheinast.eu/tag/calculator/ http://scheinast.eu/wp-admin/post.php?post=1542&action=edit http://scheinast.eu/calculator-in-c/#respond http://scheinast.eu/wp-admin/profile.php http://scheinast.eu/wp-login.php?action=logout&redirect_to=http%3A%2F%2Fscheinast.eu%2Fcalculator-in-c%2F&_wpnonce=a768d8990f http://scheinast.eu/new-hompage-design/ http://scheinast.eu/backtrack-how-to/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ https://www.addtoany.com/share_save#url=http%3A%2F%2Fscheinast.eu%2Fcalculator-in-c%2F&title=Calculator%20in%20C%2B%2B%20%7C%20Paul%20Scheinast&description=This%20is%20my%20calculator%20in%20C%2B%2B%20with%20in-line%20assembler%3A%20%5Bcrayon-556e97ccb93bc417229824%2F%5D%20Compile%20the%20code%3A%20%5Bcrayon-556e97ccb93e1826855153%2F%5D%20output%3A%20%5Bcrayon-556e97ccb93f8566053665%2F%5D... http://scheinast.eu/calculator-in-c/#wp-toolbar http://scheinast.eu/wp-admin/about.php http://scheinast.eu/wp-admin/about.php https://wordpress.org/ https://codex.wordpress.org/ https://wordpress.org/support/ https://wordpress.org/support/forum/requests-and-feedback http://scheinast.eu/wp-admin/admin.php?page=wp-statistics/wp-statistics.php http://scheinast.eu/wp-admin/admin.php?page=wps_online_menu http://scheinast.eu/wp-admin/admin.php?page=wp-statistics/wp-statistics.php http://scheinast.eu/wp-admin/ http://scheinast.eu/wp-admin/ http://scheinast.eu/wp-admin/themes.php http://scheinast.eu/wp-admin/customize.php?url=http%3A%2F%2Fscheinast.eu%2Fcalculator-in-c%2F&autofocus%5Bsection%5D=themes http://scheinast.eu/wp-admin/customize.php?url=http%3A%2F%2Fscheinast.eu%2Fcalculator-in-c%2F http://scheinast.eu/wp-admin/widgets.php http://scheinast.eu/wp-admin/customize.php?url=http%3A%2F%2Fscheinast.eu%2Fcalculator-in-c%2F&autofocus%5Bpanel%5D=widgets http://scheinast.eu/wp-admin/nav-menus.php http://scheinast.eu/wp-admin/themes.php?page=custom-background http://scheinast.eu/wp-admin/customize.php?url=http%3A%2F%2Fscheinast.eu%2Fcalculator-in-c%2F&autofocus%5Bcontrol%5D=background_image http://scheinast.eu/wp-admin/themes.php?page=custom-header http://scheinast.eu/wp-admin/customize.php?url=http%3A%2F%2Fscheinast.eu%2Fcalculator-in-c%2F&autofocus%5Bcontrol%5D=header_image http://scheinast.eu/wp-admin/edit-comments.php http://scheinast.eu/wp-admin/post-new.php http://scheinast.eu/wp-admin/post-new.php http://scheinast.eu/wp-admin/media-new.php http://scheinast.eu/wp-admin/post-new.php?post_type=page http://scheinast.eu/wp-admin/user-new.php http://scheinast.eu/wp-admin/post.php?post=1542&action=edit http://scheinast.eu/wp-admin/profile.php http://scheinast.eu/wp-admin/profile.php http://scheinast.eu/wp-admin/profile.php http://scheinast.eu/wp-login.php?action=logout&_wpnonce=a768d8990f http://scheinast.eu/wp-login.php?action=logout&_wpnonce=a768d8990f http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ https://www.addtoany.com/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/ http://scheinast.eu/calculator-in-c/

#javascript #xpath

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New Post has been published on http://scheinast.eu/javascript-string-contains/

JavaScript string contains

This is a simple function in JavaScript, I use it to check if a string contains another string.The different in this function is that the return value is the position+1.So you could use it in an If without to check the return value manually, just see my Test from 1 to 3.

This is the function:

function string_contains(str,needle) return(str.indexOf(needle)+1);

Now we make a little test to see if it work:

//Test 1 if(string_contains("abcdef","a")) console.log("abcdef contains a"); else console.log("abcdef not contains a"); //Test 2 if(string_contains("abcdef","b")) console.log("abcdef contains b"); else console.log("abcdef not contains b"); //Test 3 if(string_contains("abcdef","z")) console.log("abcdef contains z"); else console.log("abcdef not contains z");

Seems good:

abcdef contains a abcdef contains b abcdef not contains z

#contains #javascript

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New Post has been published on http://scheinast.eu/perl-reference-vs-prototype-benchmark/

Perl reference vs. prototype vs. return Benchmark

This is a little Perl Script where I try to test what way is faster, I test a normal reference in a sub vs. the prototype reference vs. normal access to a variable in a sub and then return the result, here is my Benchmark code:

use Benchmark qw(:all) ; use strict; # test variable my $x = 0; my $y = 0; my $c = 0; # run test inc_ref(\$x) for(0..10); inc_prot($y) for(0..10); $c = inc_ret($c) for(0..10); # print test print "TEST:$x-$y-$c\n"; # run benchmark cmpthese(-4, 'ref' => sub inc_ref(\$x);, 'prot' => sub inc_prot($y);, 'return' => sub $c = inc_ret($c);, ); # increment with reference sub inc_ref ++$$_[0]; # increment with reference (prototype) sub inc_prot(\$) ++$_[0]; # increment with return sub inc_ret return(++$_[0]);

Our test result:

TEST:11-11-11 Rate return ref prot return 2231497/s -- -30% -63% ref 3207033/s 44% -- -46% prot 5993929/s 169% 87% --

#Benchmark #perl #prototype

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Perl use strict only for debugging

In Perl you could turn off modules you do not need, like this:

use constant DEBUG => 0 ; use if DEBUG,strict;

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JavaScript element exists

This is a JavaScript Function to check if an element exists, I use it regularly in an If.

The function:

function element_exists (elem) return((elem)?1:0);

The test:

//Test1 if(element_exists(document.getElementById("masthead"))) console.log("element exists"); else console.log("element not exists"); //Test2 if(element_exists(document.getElementById("masthead1"))) console.log("element exists"); else console.log("element not exists");

Our result:

element exists element not exists

We could see it works as it should.

#javascript

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GNU/Linux

In this article I wrote about the Linux-Kernel and the GNU-Project, together they are called GNU/Linux.It is an Unix like Operating system and in the most cases POSIX-compliant and open source.The Kernel was firs released in the year 1991 from Linus Torvalds.

GNU/Linux is often used for Servers, there are a lot of open source software for work, a very powerful Shell and you have always Perl on the System.And the System needs not as much resources as Microsoft Systems.

I regularly use Debian or Mint,Debian is more stable, more for Servers and you could make a minimal installation with or without an GUI.Mint is more for Desktop users with a good looking Desktop.

For more take a look in the GNU/Linux Bash – Category

#bash #server

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Perl

Perl – Practical Extraction and Report Language is a free high-level, interpreted, dynamic programming language written by Larry Wall in the year 1987.Perl is very good for shell scripting and regualar expression.If you use GNU/Linux is default installed, on windows you have to install ActivePerl.The languages includes Perl 5 and 6, I use primary Perl 5(Perl 5 is also continue developing).The symbol of the Perl language is the Camel symbol.

Variable

$ for Scalar,@ for Array and % for Hashes, as example:

my $name = "test"; my @name = ("test1","test2"); my %name = ("key1" => "test1","key2" => "test2");

In Perl all variables are Scalars, you could store numbers and strings in the same value without convert.If you want to add a Scalar to another you have to concate two strings with “.”, but if you want to add two number you should use “+”.To access an element from the array you could use “$name[0]”, it starts from 0 to the last element, you get the last element with “$#name”.For manipulating a Perl Array look at this Post.

Quoting

Be careful with quoting, the double quotes could interpolate other Scalars.

my $a = "1"; my $name1 = "$a"; my $name2 = '$a';

The name1 is “1” and name2 is “$a”.

an simple “Hello World!” example:

print "Hello World!\n";

Comparison

To compare the Scalars you could use them from this table:

compare type number string equal == eq not equal != ne less than < lt greater than > gt less or equal <= le greater or equal >= ge

loops

In Perl are more than one way to make a loop:

for(1..10)... for(my $i=1;$i<=10;$i++)..

the first one is faster and faster to write, but the second has more possibility’s to change.

Do-While loop:

do ... while(1);

While loop:

while(1) ...

Optimizing

Perl is an interpreted language and if you need more performance you could use Inline code like C or you could take a look at my Benchmarks.

If you want to see some examples and solution from me see into my Category – Perl or if you want to see some special Tricks in Perl.

#comparison #concate #loop #perl #print #variable

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XPATH

The XPATH(XML Path Language) is a query language from the W3C, it is used to select nodes in an XML file.

Full Path

/html/body/div

In this example I start with “/” that say we start on root and then i navigate from element to element.

Any ware

//a

In this example I use the “//” to search in the full document to find all a nodes.(you could use the “//” behind a “/” like “/html/body/div//a” to find all elements in html body div.)

Attributes

//div[@class="secondary"]

you could use the “@” to find all elements wit the attribute class that is the string “secondarary”.

As example you could select all hrefs where the Attributes contains a string:

//a[contains(@href,"scheinast")]

Or select all hrefs where the text from the URL contains a string:

//a[contains(text(),"Scheinast")]

Array

//a[1]

If you select all Elements you get an Array, in the example above I select the firs element from my result Array.You should avoid this, better is to navigate over the class or ID because if the Page changes a bit the XPATH don’t work any more.

That are some basics, if you need something special take a look into the Network or on my page.As example Web crawling in PHP or Perl.

#html #javascript #perl #php #xpath

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Regular expression

A regular expression is a search pattern, its very often used in the programming language Perl, but it is used in other programming languages too or Text editors.

Meta characters

char meaning ^ defines the end of the matching String $ defines the end of the matching String . matches any character but not newline * matches from 0 to infinity times + matches from 1 to infinity times ? matches 0 or 1 times matches exact the given number or range | logical or operator () makes a group to store the result [] makes a character matching group

Matches

\t tabulator \n new line \r return (CR) \w matches from a-z,A-Z,0-9 and “_”. \W matches nothing from a-z,A-Z,0-9 and “_”. \s matches space, tab and newline \S matches nothing from space, tab and newline \d matches from 0-9 \D matches nothing from 0-9

Examples

This matches every string that starts with an “a”.

This pattern matches every string that end with an “a”.

^schools?$

This regex would match “schools” and “school”.

^.3,4$

Would match every string with the length between 3 and 4.

^school$|^schools$

This also would match “schools” and “school”.

"(\w)+"

On this “this is an ‘test’.” the pattern would store “test”.

[aco]+

This regex matches every combination from “a”,”c” and “o” like the word “coca”.

#regex

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