To change text in an html document or web page, we can use javascript.
If we were using php to echo the html then unfortunately, once the echo is done, the html is created so to speak and it's no longer possible to change or update it.
But, we can use javascript, as per the example below, where the 1st line could be high up on the page and would display old text and once the script below runs, this old text would be changed to new text.
This can of course be done by embedding php echo statements to include variables, which is also a way of passing a variable from php to javascript.
<p align="left" id="id1">old text</p>
<script>
document.getElementById("id1").innerHTML = "new text";
</script>
OR
<script>
document.getElementById("dt").innerHTML = "<?php echo $someVar ?>";
</script>
Thursday 30 April 2020
Tuesday 28 April 2020
basic web page redirect or reload
The following is a basic web page redirect;
<html>
<head>
<meta HTTP-EQUIV="refresh" CONTENT="3; URL=index.html">
</head>
</html>
The following is a basic javascript equivalent;
<script>
setTimeout(function ()
{
// 5 seconds
window.location.href= 'index.html';
}, 5000);
</script>
To reload a page without getting an alert, we can do the following;
<script>
function reload_page()
{
window.location = window.location.href;
}
</script>
function reload_page()
{
window.location = window.location.href;
}
</script>
then call it by;
<script type="text/javascript">
reload_page();
</script>';
or from php;
echo '<script type="text/javascript">'.'reload_page();'.'</script>';
To call the function after some time, for example, to refresh the page in 5 seconds, we can do the following to call the reload_page function detailed above;
<script>
setTimeout(reload_page,5000);
</script>
Sign Magnitude, Two's compliment binary representations
The following table shows the difference between Sign Magnitude and Two's compliment
As an additional note, two's compliment involves inverting and adding 1.
So if we look at the table below for 0100 which is 4, the two's compliment representation of -4 would be 1100
How do we get there, well we first invert from 0100 to 1011 and then add 1 to give 1100
To go the other way;
If we have -3 which is 1101 we invert to give 0010 and add 1 to give 0011 which is of course 3
As an additional note, two's compliment involves inverting and adding 1.
So if we look at the table below for 0100 which is 4, the two's compliment representation of -4 would be 1100
How do we get there, well we first invert from 0100 to 1011 and then add 1 to give 1100
To go the other way;
If we have -3 which is 1101 we invert to give 0010 and add 1 to give 0011 which is of course 3
Saturday 18 April 2020
Add a Right Click action to any Application
The following is an automator screenshot of how to add a Right Click action to highlighted text in any application on a Mac.
Thursday 16 April 2020
Cyclomatic Complexity
Cyclomatic Complexity
Cyclomatic Complexity is the number of independent paths through code and there are many websites that do a better job of explaining it than I can, but...
Wednesday 8 April 2020
To test a fail2ban filter using fail2ban-regex
We can test any fail2ban filters by using the following:
fail2ban-regex <logfile> <filter>
Example:
fail2ban /var/log/apache/error_log /etc/fail2ban/filter.d/apache-noscripts.conf
fail2ban-regex <logfile> <filter>
Example:
fail2ban /var/log/apache/error_log /etc/fail2ban/filter.d/apache-noscripts.conf
Tuesday 7 April 2020
To block, unblock or check IP addresses with iptables in Linux
To block or check IP addresses with iptables
The format to block and IP address is as follows:
iptables -A INPUT -s BAN-IP-ADDRESS -j DROP
iptables -A INPUT -s BAN-IP-ADDRESS/MASK -j DROP
To block an IP address, use the following;
iptables -A INPUT -s 192.168.254.100 -j DROP
To view all blocked IP addresses, do;
iptables -L INPUT -v -n
OR
iptables -L INPUT -v -n | less
OR (especially if blocked with fail2ban) **
iptables -L -n --line
To check for a specific IP address, do;
iptables -L INPUT -v -n | grep "192.168.254.100"
To unblock an IP address, do;
iptables -D INPUT -s 192.168.254.100 -j DROP
Alternatively to unblock an entry blocked with fail2ban (see ** above) do;
iptables -L -n --line
then find the IP address you wish to unban.
then do
iptables -D ruleName n
where ruleName is the rule name associated with the banned IP
and n is the number associated with the banned IP
ref: https://www.cyberciti.biz/faq/linux-howto-check-ip-blocked-against-iptables/
The format to block and IP address is as follows:
iptables -A INPUT -s BAN-IP-ADDRESS -j DROP
iptables -A INPUT -s BAN-IP-ADDRESS/MASK -j DROP
To block an IP address, use the following;
iptables -A INPUT -s 192.168.254.100 -j DROP
To view all blocked IP addresses, do;
iptables -L INPUT -v -n
OR
iptables -L INPUT -v -n | less
OR (especially if blocked with fail2ban) **
iptables -L -n --line
To check for a specific IP address, do;
iptables -L INPUT -v -n | grep "192.168.254.100"
To unblock an IP address, do;
iptables -D INPUT -s 192.168.254.100 -j DROP
Alternatively to unblock an entry blocked with fail2ban (see ** above) do;
iptables -L -n --line
then find the IP address you wish to unban.
then do
iptables -D ruleName n
where ruleName is the rule name associated with the banned IP
and n is the number associated with the banned IP
ref: https://www.cyberciti.biz/faq/linux-howto-check-ip-blocked-against-iptables/
Set and retrieve cookies with php
The format for setting a cookie in php is as follows:
setcookie(name, value, expire, path, domain, security);
I only use the name, value and expire, where expire is in seconds, so;
time() + 24*60*60 is 1 day.
setcookie(name, value, expire, path, domain, security);
I only use the name, value and expire, where expire is in seconds, so;
time() + 24*60*60 is 1 day.
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