|| use Vs require in perl || What is the difference between use and require?

Except of course that use is evaluated at compile time where as require is evaluated at run time in other word, A use anywhere in the code will be evaluated when the code is run compiled, but require – import’s can only get evaluated when encoutered.

The differences are many and often subtle:

1. use only expects a bareword, require can take a bareword or an expression
2. use is evaluated at compile-time, require at run-time
3. use implicitly calls the import method of the module being loaded, require does not
4. use excepts arguments in addition to the bareword (to be passed to import), require does not
5. use does not behave like a function (i.e can’t be called with parens, can’t be used in an expression, etc), whereas require does

do $file is like eval `cat $file`, except the former:
1.1: searches @INC and updates %INC.
1.2: bequeaths an *unrelated* lexical scope on the eval’ed code.

require $file is like do $file, except the former:
2.1: checks for redundant loading, skipping already loaded files.
2.2: raises an exception on failure to find, compile, or execute $file.

require Module is like require “Module.pm”, except the former:
3.1: translates each “::” into your system’s directory separator.
3.2: primes the parser to disambiguate class Module as an indirect object.

use Module is like require Module, except the former:
4.1: loads the module at compile time, not run-time.
4.2: imports symbols and semantics from that package to the current one.

Command to learn more about use and require
> perldoc -f require
> perldoc -f use

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Checking File Attributes in Perl

I have been using perl for quite some time now. I have also been using the file handling logic in my scripts. However, what I did not know till now is that you can quickly check for certain file properties in perl. Here is an example:
#!/usr/bin/perl
my (@description,$size);
if (-e $file)
{
push @description, ‘binary’ if (-B _);
push @description, ‘a socket’ if (-S _);
push @description, ‘a text file’ if (-T _);
push @description, ‘a block special file’ if (-b _);
push @description, ‘a character special file’ if (-c _);
push @description, ‘a directory’ if (-d _);
push @description, ‘executable’ if (-x _);
push @description, (($size = -s _)) ? “$size bytes” : ‘empty’;
print “$file is “, join(‘, ‘,@description),”\n”;
}
Nice, isn’t it?
Here is the complete list of features that you can check:

The post How to Check File Attributes in Perl ? Perl File Attributes explained appeared first on scmGalaxy.