In terms of scoping, there are three kinds of variables in Perl. Lexical variables are lexically scoped, which means they are only visible in the current lexical scope (basically file or block). Package variables, on the other hand, can be used using their qualified form (e.g. $Foo::x) from anywhere in the interpreter, and they can … Read more
These modules you can acheive the extract text from pdf PDF::API2 CAM::PDF CAM::PDF::PageText From CPAN my $pdf = CAM::PDF->new($filename); my $pageone_tree = $pdf->getPageContentTree(1); print CAM::PDF::PageText->render($pageone_tree); This module attempts to extract sequential text from a PDF page. This is not a robust process, as PDF text is graphically laid out in arbitrary order. This module uses … Read more
fgrep -x -f file2 -v file1 -x match whole line -f FILE takes patterns from FILE -v inverts results (show non-matching)
When I started out using Perl it was explained to me that these characters were chosen because: $ looked a bit like an ‘s’ so that was for scalars, @ has an ‘a’ in the middle so that was for arrays, and % was for hashes because it looked like a key-value pair divided by … Read more
It’s a nasty little idiom for setting autoflush on a filehandle other than STDOUT. select() takes the supplied filehandle and (basically) replaces STDOUT with it, and it returns the old filehandle when it’s done. So (select($s),$|=1) redirects the filehandle (remember select returns the old one), and sets autoflush ($| = 1). It does this in … Read more
It may be relevant that Perl never gives memory back to the system by itself: It’s all up to malloc() and all the rules associated with that. Knowing how malloc() allocates memory is important to answering the greater question, and it varies from system to system, but in general most malloc() implementations are optimized for … Read more
If you want to securely quote anything for Bash, you can use its built-in printf %q formatting: cat strings.txt: yes no Hello, world C:\Program Files\ ” \ \\ \\\ \\\\ \\\\\ “\ “\T “\\T !1 !A “!\/'” “Jeff’s!” $PATH %PATH% & <>|&^ *@$$A$@#?-_ cat quote.sh: #!/bin/bash while IFS= read -r string do printf ‘%q\n’ “$string” … Read more
There are (rather too) many ways to do this in Perl because there are so many ways to do things in Perl. As someone commented, autoloaded methods will always be a bit tricky. However, rather than rolling your own approach I would suggest that you take a look at Class::Inspector on CPAN. That will let … Read more
If you have to hard code #!, use #!/usr/bin/env perl. Why? What you want is for the Perl program to run with the user’s preferred Perl. That’s going to be the first on in their PATH. #!perl doesn’t do what I mean, it doesn’t search the user’s PATH, #!/usr/bin/env perl is how you pull that … Read more
Standard practice is to use use most of the time, require occasionally, and do rarely. do ‘file’ will execute file as a Perl script. It’s almost like calling eval on the contents of the file; if you do the same file multiple times (e.g. in a loop) it will be parsed and evaluated each time … Read more