Answer:

To un-compress a Java Web Archives file (*.war), you can use the command

# jar xvf my-app.war

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Answer:

To print a string of "Hello World" to the standard output in different scripting languages

1. Perl

print "Hello, World!";

2. Python

print('Hello, World!')

3. PHP

echo "Hello, World!";

4. Ruby

puts "Hello, World!"

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Answer:

In Perl, you can enforce using the strict mode to reduce the chance of nasty error, e.g.

$foo = 'bar';
print $foo;

If you run the above problem, it is completely valid.

# perl test.pl
bar

However, if you use the strict pragma

use strict;

$foo = 'bar';
print $foo;

And run the program again..

# perl test.pl
Global symbol "$foo" requires explicit package name at test.pl line 3.
Global symbol "$foo" requires explicit package name at test.pl line 4.
Execution of test.pl aborted due to compilation errors.

Since the $foo is not declared before the first use, so the compilation stopped. In modern Perl developements, it is recommended to alwasys use the strict pragma in order to write a better and maintainable program.

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Answer:

By default, node modules installed using simple node install will be installed under the folder ./node_modules. In order to install the modules globally, try

# sudo npm install express -g

The above command install the express module as global module.

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Answer:

npm is a package manager for node.js, to install it under Linux, just a single command:

# curl http://npmjs.org/install.sh | sudo sh

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Answer:

In order to install NodeJS in Linux, the recommended way is compile from source and install it.

# wget http://nodejs.org/dist/node-v0.4.11.tar.gz
# tar zxf node-v0.4.11.tar.gz
# cd node-v0.4.11
# ./configure
# sudo make && make install

Now you can type node to enter the node's REPL

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Answer:

In PHP, to remove object (e.g. with the key = foo in the following example) from array inside foreach loop, you can try:

<?php

foreach($array as $key=> $value) {
    if ($key == "foo") {
        unset($array[$key]);
    }
}

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Answer:

The following script demonstrates how to check if a file exist, using shell (Bash) script

#!/bin/bash

if [ -e test.txt ]
then
  echo 'The file exists.'
else
  echo 'The file does not exist.'
fi

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Answer:

If you are using PHP 5.2 or above (in fact, at the moment of writing, you should use at least PHP 5.3+), you can use the following easy method:

if(filter_var($ip, FILTER_VALIDATE_IP))
{
  // Valid IP
}
else
{
  // Invalid IP
}

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Answer:

To get the current PHP include path's setting, you can use the function get_include_path

E.g.

echo get_include_path();

Usually it is used with the set_include_path for adding extra path to the existing include_path,

E.g.

set_include_path(get_include_path() . PATH_SEPARATOR . "/data/path");

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