Xenomai Timer

Xenomai Timer :Xenomai has two time sources: the sytem timer, which counts the number of nanoseconds since 1970, and a hardware dependent high resolution counter which counts the time since an unspecified point in time (usually the system boot time). This hardware dependent high resolution counter is called “tsc” on a PC, and gave its name to Xenomai native API calls.rt_timer_tsc returns the value of this hardware dependent high-resolution counter.
rt_timer_info returns the same thing in the tsc member of the RT_TIMER_INFO structure, and the value of the system timer at exactly the same time as when the high-resolution counter was read.

This allows to have a correspondence between the two time sources.

rt_alarm_inquire is not related to this and returns some information
about a given alarm. Now, if you allow me, a little advice for the implementation of a “timer library”: you could be tempted to create only one periodic alarm object with Xenomai, and to manage a timer list yourself. Don’t do this. Creating an alarm object for each timer library object make Xenomai aware of the existence of all your application timers, this has several

– it gives you information about all your timers in /proc/xenomai
– it allows Xenomai to use its anticipation algorithm for all your timers
– if you are concerned about the scalability of Xenomai timers list
management, you can check the options in the “Scalability” menu of
Xenomai configuration menu (“Real-time subsystem” sub-menu of kernel
configuration menu).
more about timers

Xenomai POSIX skin supports two clocks:
CLOCK_REALTIME maps to the nucleus system clock, keeping time as the amount of time since the Epoch, with a resolution of one system clock tick.

CLOCK_MONOTONIC maps to an architecture-dependent high resolution counter, so is suitable for measuring short time intervals. However, when used for sleeping (with clock_nanosleep()), the CLOCK_MONOTONIC clock has a resolution of one system clock tick, like the CLOCK_REALTIME clock.[1]

OpenSSL “HeartBleed” Bug


Monday afternoon, the IT world got a very nasty wakeup call, an emergency security advisory from the OpenSSL project warning about an open bug called “Heartbleed.” The bug could be used to pull a chunk of working memory from any server running their current software. There was an emergency patch, but until it was installed, tens of millions of servers were exposed. Anyone running a server was suddenly in crisis mode.

If the “Heartbleed” name sounds dramatic, this bug seems to live up to the hype. It’s already far worse than the GoToFail bug that embarrassed Apple earlier this year, both by the scale of computers affected and the depth of the breach. The new bug would let attackers pull the private keys to the server, letting attackers listen in on data traffic and potentially masquerade as the server. Even worse, it’s old: the bug dates back two years, and it’s still unclear how long anyone’s known about it.

OpenSSL isn’t widely known outside of the coding world, but as many as two out of three servers on the web rely on its software. The sudden reveal means anyone involved is now scrambling for a fix. Already, Yahoo has been exposed by the bug, and experts have advised any Yahoo users to steer clear of their accounts until the company has time to update their servers. (A Yahoo representative tells The Verge the core sites are now patched, although the team is still working to implement the fix across the rest of the site.) Dozens of other smaller companies have also reportedly been affected, including Imgur, Flickr, and LastPass (although LastPass says no unencrypted data was exposed). “It is catastrophically bad, just a hugely damaging bug,” says ICSI security researcher Nicholas Weaver.

Discovered by Google researcher Neel Mehta, the bug allows an attacker to pull 64k at random from a given server’s working memory. It’s a bit like fishing — attackers don’t know what usable data will be in the haul — but since it can be performed over and over again, there’s the potential for a lot of sensitive data to be exposed. The server’s private encryption keys are a particular target, since they’re necessarily kept in working memory and are easily identifiable among the data. That would allow attackers to eavesdrop on traffic to and from the service, and potentially decrypt any past traffic that had been stored in encrypted form.

For most privacy tools relying on OpenSSL, the takeaway is catastrophic. A blog post from the Tor Project told users, “if you need strong anonymity or privacy on the internet, you might want to stay away from the internet entirely for the next few days while things settle.” In many cases, a few days may not be enough. It will give services time to patch their servers, but if any private keys were compromised before the patch went up, it would give attackers free rein in the months to come. Servers can reset their certificates, but it’s slow and expensive, and experts suspect many of them may simply assume the patch is enough. “I bet that there will be a lot of vulnerable servers a year from now,” Weaver says. “This won’t get fixed.”

Apple, Google and Microsoft appear to be unaffected, along with the major e-banking services. Yahoo, on the other hand, was affected and leaking user credentials for a significant portion of the day before its core sites were fixed. More generally, any server running OpenSSL on Apache or Nginx will be affected, which implicates a huge variety of everyday websites and services.

For now, there are a few ways users can tell which services are safe — but the news isn’t reassuring. This site, built by developer Filippo Valsorda, offers a spot-check as to which services are currently unpatched, but the site’s code is also producing false negatives, so it shouldn’t be taken as definitively ruling anything out. Any patched server will also need to generate new SSL certificates to make sure attackers can’t use keys that were exposed in the breach. To check, use an SSL tracker like this one and look for a certificate’s “issued on” date, which should be dated after the recent patch. Resetting the certificates will take time and money, but if a compromised site keeps using a compromised certificate, they’ll be leaving themselves open to an attack.

It’s still early to tell what larger changes will be made as a result of the breach, but some lessons are already clear. Despite the vast infrastructure relying on OpenSSL, the open-source project is comparatively underfunded, and some experts have already called for more donations to the project to prevent vulnerabilities like Heartbleed from slipping through the cracks. Perfect Forward Secrecy could also have limited the damage from the bug, preventing decryption after the fact.

But the most troubling lesson might be how hard vulnerabilities are to discover, and how damaging they can be once fully revealed. “These are really subtle bugs,” Weaver says. “You might detect it if you ran it through a memory checker, but this is not the kind of thing that just shows up looking at the code.” That’s a credit to Google, who was rigorous enough to discover the bug — but for anyone relying on secure software, it’s a troubling thought.

Some Comments about clarification of the posts.

  • The answer to this question is “maybe”. The article here has several points wrong, one of them being that the attacker cannot select which data they are going to have leak. The flaw basically blows out a memory register and returns whatever data happens to be in the extra bytes. It could be something, or, in most cases, it could be nothing. To get useful data, you would have to flood the server with TLS “heartbeat” requests.
  • As someone familiar with this tech, I’d say the author of this article did a decent job covering the main bases. The possibilities are huge. Getting a 64k chunk of random memory is pretty significant. There are just over 262,000 64k chunks in a 16GB server. An attacker can muster 262,000 requests in just a few minutes. Once the random jabs have shaken loose pretty much all the contents of the server’s memory, then the attacker can sift through the responses for the private SSL keys. The private SSL keys can be used by the attacker to imitate the host to visiting browsers, which will then submit login info. Having the server’s private SSL key can also greatly simplify a Man-in-the-middle attack on sessions that are supposed to be private between the browser and the server. Finally, the private SSL key also enables previously-captured network traffic to be fully decrypted.
  • The article is confusing about what the potential leakage is. There is the potential that an attacker could get any kind of data that was loaded into memory, which makes the bug nasty. But it’s not like an attacker could just hit the server and pull everything in memory, or download a specific kind of data. They would have to send millions of heartbeat requests just to guarantee that they got any useful data. And it still wouldn’t be guaranteed.I’m not trying to downplay the seriousness of the issue, but it’s probably not likely that people need to freak out about all their data being stolen right now. The serious concern is the loss of server private keys, so people should go through the process of updating their servers and re-keying their SSL certificates to ensure that they are safe.
  • No it doesn’t; it allows an attacker to see the contents of a small portion of RAM immediately following a chunk of RAM that OpenSSL uses. They have no control over what specific portion of memory it is nor what it contains; it could be anything and what it is exactly really depends on a bunch of pretty much random factors.The concern is that there is a possibility that it could contain something important (like the servers private encryption keys) which would obviously be a problem. This is where the verge article delves into sensationalist BS however they can’t write software that is essentially “push button to steal certs” this would take time and resources to exploit in any meaningful way unless the attacker was very lucky. Again, this is basically like trying to steal someone’s password by walking behind their desk hoping that they happen to be typing it in as you walk by.It’s a big deal because relying on someone not getting lucky is not a good form of security, the chances that this was exploited in a meaningful way is almost nil.

All technical knowledge about Open Ssl 1.0.1

An information disclosure vulnerability has been found, and promptly patched, in OpenSSL.

OpenSSL is a very widely used encryption library, responsible for putting the S in HTTPS, and the padlock in the address bar, for many websites.

The bug only exists in the OpenSSL 1.0.1 source code (from version 1.0.1 to 1.0.1f inclusive), because the faulty code relates to a fairly new feature known as the TLS Heartbeat Extension.

The heartbeat extension was first documented in RFC 6520 in February 2012.

TLS heartbeats are used as “keep alive” packets so that the ends of an encrypted connection can agree to keep the session open even when they don’t have any official data to exchange.

Because the heartbeats consist of a reply and a matching response, they allow either end to confirm not only that the session is open, but also that end-to-end connectivity is working properly.

Sending heartbeat requests

The RFC 6520 standard explicitly restricts the maxium size of a heartbeat request to 214 bytes (16KBytes), but OpenSSL itself generates far shorter requests.

Don’t worry if you don’t understand C; but if you do, the OpenSSL heartbeat request code looks like this:

unsigned int payload = 18; /* Sequence number + random bytes */
unsigned int padding = 16; /* Use minimum padding */

/* Check if padding is too long, payload and padding
* must not exceed 2^14 - 3 = 16381 bytes in total.

OPENSSL_assert(payload + padding <= 16381);

/* Create HeartBeat message, we just use a sequence number
 * as payload to distuingish different messages and add
 * some random stuff.
 *  - Message Type, 1 byte
 *  - Payload Length, 2 bytes (unsigned int)
 *  - Payload, the sequence number (2 bytes uint)
 *  - Payload, random bytes (16 bytes uint)
 *  - Padding

buf = OPENSSL_malloc(1 + 2 + payload + padding);
p = buf;
/* Message Type */
/* Payload length (18 bytes here) */
s2n(payload, p);
/* Sequence number */
s2n(s->tlsext_hb_seq, p);
/* 16 random bytes */
RAND_pseudo_bytes(p, 16);
p += 16;
/* Random padding */
RAND_pseudo_bytes(p, padding);

ret = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buf, 3 + payload + padding);

The reason that the code says that “payload and padding must not exceed 16381 bytes in total” is that the 16KByte (16384 byte) maximum heartbeat request size includes one byte to signal that this is a TLS1_HB_REQUEST, and two bytes to denote the length of the payload data in the request.

As the code stands, the OPENSSL_assert to verify that payload + padding <= 16381 is redundant, because the payload size is hard-wired to 18 bytes and the padding size to 16.

But the programmer has tried to do the right thing: put in the check anyway, in case someone changes those payload or padding sizes in the future without considering the consequences.

The code then transmits a heartbeat request consisting of:

  • The single byte 0x01 (denoting that this is a TLS1_HB_REQUEST).
  • Two bytes containing the 16-bit representation of 34 (size of payload plus padding).
  • Two bytes of payload consising of a 16-bit sequence number.
  • 16 bytes of random data making up the rest of the 18-byte payload.
  • 16 further random padding bytes, required by the standard.

Replying to heartbeat requests

When vulnerable versions of OpenSSL 1.0.1 respond to a heartbeat request, they aren’t quite so careful in processing the received data.

Heartbeat replies are supposed to contain a copy of the payload data from the request, as a way of verifying that the encrypted circuit is still working both ways.

It turns out that you can send a small heartbeat request, but sneakily set your payload length field to 0xFFFF (65535 bytes).

Then, OpenSSL will uncomplainingly copy 65535 bytes from your request packet, even though you didn’t send across that many bytes:

/* Allocate memory for the response, size is 1 byte
 * message type, plus 2 bytes payload length, plus
 * payload, plus padding
buffer = OPENSSL_malloc(1 + 2 + payload + padding);
bp = buffer;

/* Enter response type, length and copy payload */
s2n(payload, bp);
memcpy(bp, pl, payload);
bp += payload;
/* Random padding */
RAND_pseudo_bytes(bp, padding);

r = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buffer, 3 + payload + padding);

That means OpenSSL runs off the end of your data and scoops up whatever else is next to it in memory at the other end of the connection, for a potential data leakage of approximately 64KB each time you send a malformed heartbeat request.

This bug has been rather melodramatically named “heartbleed,” for reasons that should now be obvious.

According to the Finnish National Cyber Security Centre, the sort of data that “bleeds” when the bug is triggered varies enormously, but may includemessage contents, user credentials, session keys and even copies of a server’s own private keys.

That’s not good!

Fixing the problem

Fortunately, there’s a fix already: simply upgrade to OpenSSL 1.0.1g.

If you don’t want to or can’t do that, you can rebuild your current version of OpenSSL from source without TLS Heartbeat support, by adding -DOPENSSL_NO_HEARTBEATS at compile time.

Both of these immunise you from this flaw.

The new OpenSSL version includes a bounds check to make sure the payload length you specified isn’t longer that the data you actually sent:

/* Read type and payload length first */
if (1 + 2 + 16 > s->s3->rrec.length)
        return 0; /* silently discard */
hbtype = *p++;
n2s(p, payload);
if (1 + 2 + payload + 16 > s->s3->rrec.length)
        return 0; /* silently discard per RFC 6520 sec. 4 */

The -DOPENSSL_NO_HEARTBEATS compile-time option simply omits the buggy code altogether from vulnerable versions.

The lessons to learn

If you’re a programmer, remember: always double-check the data that the other side sent you before you use it to control the operation of your own code.

And remember: buffer overflows should always be treated as serious, even if they don’t lead to remote code execution.

Data leakage bugs can be just as disastrous, as this flaw demonstrates.

For further information…

If you’d like to know more about the main sorts of vulnerablity, from RCE (remote code execution) through EoP (elevation of privilege) to Information Disclosure, please listen to our Techknow podcastUnderstanding Vulnerabilities.

This post totally copied from “The Verge” and “SOPHOS“. This is just an informative post.

Understanding Xenomai

Before understanding Xenomai it’s really important to understand the Normal Linux os and Real Time OS and how they execute their instructions.
Definition from Xenomai’s Website : Xenomai is a real-time development framework cooperating with the Linux kernel, in order to provide a pervasive, interface-agnostic, hard real-time support to user-space applications, seamlessly integrated into the GNU/Linux environment. Xenomai is based on an abstract RTOS core, usable for building any kind of real-time interfaces, over a nucleus which exports a set of generic RTOS services. Any number of RTOS personalities called “skins” can then be built over the nucleus, providing their own specific interface to the applications, by using the services of a single generic core to implement it. Xenomai runs over seven architectures (namely ppc, blackfin, arm, x86, x86_64, ia64 and ppc64), a variety of embedded and server platforms, and can be coupled to two major Linux kernel versions (2.4 and 2.6), for MMU-enabled and MMU-less systems. Supported real-time APIs include POSIX 1003.1b, VxWorks, pSOS+, VRTX and uITRON.

## Difference between RT os and Normal OS ##

- The Linux scheduler, like that of other OSes such as Windows or MacOS, is designed for best average response, so it feels fast and interactive even when running many programs. However, it doesn’t guarantee that any particular task will always run by a given deadline. A task may be suspended for an arbitrarily long time, for example while a Linux device driver services a disk interrupt.

- Scheduling guarantees are offered by real-time operating systems (RTOSes), such as QNX, LynxOS or VxWorks. RTOSes are typically used for control or communications applications, not for general purpose computing.

- The general idea of RT Linux is that a small real-time kernel runs beneath Linux, meaning that the real-time kernel has a higher priority than the Linux kernel. Real-time tasks are executed by the real-time kernel, and normal Linux programs are allowed to run when no real-time tasks have to be executed. Linux can be considered as the idle task of the real-time scheduler. When this idle task runs, it executes its own scheduler and schedules the normal Linux processes. Since the real-time kernel has a higher priority, a normal Linux process is preempted when a real-time task becomes ready to run and the real-time task is executed immediately.

How is the real-time kernel given higher priority than Linux kernel?

Basically, an operating system is driven by interrupts, which can be considered as the heartbeats of a computer:

1. All programs running in an OS are scheduled by a scheduler which is driven by timer interrupts of a clock to reschedule at certain times.
2. An executing program can block or voluntary give up the CPU in which case the scheduler is informed by means of a software interrupt (system call).
3. Hardware can generate interrupts to interrupt the normal scheduled work of the OS for fast handling of hardware.

RT Linux uses the flow of interrupts to give the real-time kernel a higher priority than the Linux kernel:

1. When an interrupt arrives, it is first given to the real-time kernel, and not to the Linux kernel. But interrupts are stored to give them later to Linux when the real-time kernel is done.
2. As first in row, the real-time kernel can run its real-time tasks driven by these interrupts.
3. Only when the real-time kernel is not running anything, the interrupts which were stored are passed on to the Linux kernel.
4. As second in row, Linux can schedule its own processes driven by these interrupt.

Hence, when a normal Linux program runs and a new interrupt arrives:

1. It is first handled by an interrupt handler set by the real-time kernel;
2. The code in the interrupt handler awakes a real-time task;
3. Immediately after the interrupt handler, the real-time scheduler is called ;
4. The real-time scheduler observes that another real-time task is ready to run, so it puts the Linux kernel to sleep, and awakes the real-time task.
Hence, to the real-time kernel and Linux kernel coexist on a single machine a special way of passing of the interrupts between real-time kernel and the Linux kernel is needed. Each flavor of RT Linux does this is in its own way. Xenomai uses an interrupt pipeline from the [Adeos project][1]. For more information, see also [Life with Adeos][2].
[1]: http://home.gna.org/adeos/
[2]: http://www.xenomai.org/documentation/xenomai-2.3/pdf/Life-with-Adeos-rev-B.pdf


The Xenomai project was launched in August 2001.
Xenomai is based on an abstract RTOS core, usable for building any kind of real-time interfaces, over a nucleus which exports a set of generic RTOS services. Any number of RTOS personalities called “skins” can then be built over the nucleus, providing their own specific interface to the applications, by using the services of a single generic core to implement it.
The following skins on the generic core are implemented :
native: the Xenomai skin
RTAI: only in kernel threads
Xenomai allows to run real-time threads either strictly in kernel space, or within the address space of a Linux process. A real-time task in user space still has the benefit of memory protection, but is scheduled by Xenomai directly, and no longer by the Linux kernel. The worst case scheduling latency of such kind of task is always near to the hardware limits and predictable, since Xenomai is not bound to synchronizing with the Linux kernel activity in such a context, and can preempt any regular Linux activity with no delay. Hence, he preferred execution environment for Xenomai applications is user space context.
But there might be a few cases where running some of the real-time code embodied into kernel modules is required, especially with legacy systems or very low-end platforms with under-performing MMU hardware. For this reason, Xenomai’s native API provides the same set of real-time services in a seamless manner to applications, regardless of their execution space. Additionally, some applications may need real-time activities in both spaces to cooperate, therefore special care has been taken to allow the latter to work on the exact same set of API objects.
In our terminology, the terms “thread” and “task” have the same meaning. When talking about a Xenomai task we refer to real-time task in user space, i.e., within the address space of a Linux process, not to be confused with regular Linux task/thread.

Some of the most interesting & Shocking In formations about Cricket.

Hello Guys this is my first non-technical post, I would love to share some of the most shocking, interesting information about Cricket History.

1. Sanath Jayasuriya has more ODI wickets than Shane Warne : Yes it’s correct Shane warne took 293 wickets in his ODI career and Sanath took 321 wickets. It was shoking for me too.


2. On 12th January 1964, Indian spinner Bapu Nadkarni bowled 21 consecutive maiden overs vs England at Chennai. His figures were 32-27-5-0 which is an economy rate of 0.15 per over which is the lowest of all bowlers where 10 or more overs were bowled.


3. Wilfred Rhodes took 4,204 wickets in First Class cricket. No, it’s not a typo. He actually did take more than Four Thousand wickets. He also happened to score 39, 969 runs.


4. Sachin is not the highest Centuries hitter, Sir Jack Hobbs scored 199 centuries in his First Class career.


5. In a World Cup Match, chasing 335, Sunil Gavaskar scored an unbeaten 36 off 174 balls. In the Prudential World Cup of 1975, in the match between India and England, England set the target of 335 runs in 60 overs. Sunil Gavaskar batted throughout the innings and scored only 36 runs of 174 balls. India managed to score only 132 runs in 60 overs with 7 wickets in hand.


6. Sachin + Zaheer = (Almost) Kallis.


7. Sir Don Bradman has just hit 6 sixes in his entire career.

8. The England Cricket Team is the only team in ODI history to lose a 60 over ODI Final (1979 World Cup), a 50 over ODI Final (1992 World Cup and 2004 Champions Trophy) and a 20 over ODI Final (2013 Champions Trophy) in ICC tournaments.

Bash script not working with `sh`

I was testing a simple script and I was wondering why it works fine when executed from directory: ./test.sh but when I try with “sh” command sh test.sh it’s not working:
test.sh: 3: test.sh: [[: not found
test.sh: 7: test.sh: [[: not found

#!/usr/bin/env bash

if [[ $1 = one ]]
        printf "%b" "two\n" >&2
        exit 0
elif [[ $1 = two ]]
        printf "%b" "one\n" >&2
        exit 0
        printf "%b" "Specify argument: one/two\n"
        exit 1

I goggled and found this link

sh is a different program than bash.


The problem is that the Bourne shell (sh) is not the Bourne Again shell (bash). Namely, sh doesn’t understand the [[ pragma. In fact, it doesn’t understand [ either. [ is an actual program or link to /bin/test (or /usr/bin/[, /usr/bin/test).

$ which [
$ ls -lh /bin/[
-r-xr-xr-x  2 root  wheel    42K Feb 29 17:11 /bin/[

When you execute your script directly through ./test.sh, you’re calling the script as the first argument to the program specified in the first line. In this case:
#!/usr/bin/env bash
Often, this is directly the interpreter (/bin/bash, or any number of other script interpreters), but in your case you’re using env to run a program in a modified environment — but that follow argument is still bash. Effectively, ./test.sh is bash test.sh.
Because sh and bash are different shells with different syntax interpretations, you’re seeing that error. If you run bash test.sh, you should see what is expected.
More info
Others have pointed out in comments that /bin/sh can be a link or other shell. Historically, sh was the Bourne shell on the old AT&T Unix, and in my mind the canonical descent. However, that is different in BSD variations and has diverged in other Unix based systems and distributions over time. If you’re really interested in the inner workings (including how /bin/sh and /bin/bash can be the same program and behave totally differently), read the following:
[1] [2]

As noted: /bin/sh typically (though not always) invokes a POSIX-compliant Bourne shell. Bash is Not Bourne.
Bash will attempt to emulate Bourne when invoked as ‘sh’ (as when /bin/sh symlinks or links to /bin/bash), or if $POSIXLY_CORRECT is defined in the invoking environment, when invoked with the –posix invocation option, or when ‘set -o posix’ has been executed. This enables testing a Bourne shell script / command for POSIX compliance.
Alternately, invoke scripts / test commands with a known POSIX-compliant shell. ‘dash’ is close, the Korn shell (ksh) IIRC offers a POSIX compliant option as well.

Date difference with Time in (Perl)

Function validateDateDifference() can validate date difference with time also.

Validation Range is from 1900-01-01 00:00:00 to 2199-12-31 23:59:59


validateDateDifference(“Startdate time”,”Enddate time”,”dateformat”)

date format are : mmddyyyy or ddmmyyyy or yyyymmdd
(this function can support these time formats only)

Start date syntax : mm-dd-yyyy or dd-mm-yyyy or yyyy-mm-dd
you can replace “-” with “.” or “/”
for Ex. mm.dd.yyyy or mm/dd/yyyy
time syntax is : HH:MM:SS
EX. 19:10:59

Test cases :
validateDateDifference(“12.12.2013 12:12:58″,”12.12.2013 12:12:59″,”ddmmyyyy”)
validateDateDifference(“2013-01-31 12:12:58″,”2013-12-02 12:12:59″,”yyyymmdd”)

If you want to validate date only then you can use function validateDateFormat()

validateDateFormat(“date” , “dateformat”)

syntax same as above

If you want to validate time only then you can use function isvalidtime()


time syntax same as above

sub validateDateFormat{
$regexmmddyyyy='^(0[1-9]|1[012])[-/.](0[1-9]|[12][0-9]|3[01])[- /.]((?:19|20|21)\d\d)$';
$regexddmmyyyy='^(0[1-9]|[12][0-9]|3[01])[-/.](0[1-9]|1[012])[- /.]((?:19|20|21)\d\d)$';
$regexyyyymmdd='^((?:19|20|21)\d\d)[- /.](0[1-9]|1[012])[-/.](0[1-9]|[12][0-9]|3[01])$';
$format = shift;
if($format eq 'ddmmyyyy'){
if(eval $date=~$regexddmmyyyy){
$date = $1;
$month = $2;
$year = $3;
if(isvaliddate($date,$month,$year) eq "true"){
return $year.$month.$date; # Valid date
return "false"; # Not a valid date
}elsif($format eq 'mmddyyyy'){
if(eval $date=~$regexmmddyyyy){
$date = $2;
$month = $1;
$year = $3;
if(isvaliddate($date,$month,$year) eq "true"){
return $year.$month.$date; # Valid date
return "false"; # Not a valid date
}elsif($format eq 'yyyymmdd'){
if(eval $date=~$regexyyyymmdd){
$date = $3;
$month = $2;
$year = $1;
if(isvaliddate($date,$month,$year) eq "true"){
return $year.$month.$date; # Valid date
return "false"; # Not a valid date
return "false"; # Not a valid date
## HH:MM:SS is allowed only
sub isvalidtime{
$time = shift;
if(eval $time=~$regexhhmmss){
return "true";
return "false";
sub isvaliddate{
$date = shift;
$month = shift;
$year = shift;
if ($date == 31 and ($month == 4 or $month == 6 or $month == 9 or $month == 11)) {
return "false"; # 31st of a month with 30 days
}elsif ($date >= 30 and $month == 2) {
return "false"; # February 30th or 31st
} elsif ($month == 2 and $date == 29 and not ($year % 4 == 0 and ($year % 100 != 0 or $year % 400 == 0))) {
return "false"; # February 29th outside a leap year
} else {
return "true"; # Valid date
sub validateDateDifference{
$startdate = shift;
$enddate = shift;
$format =shift;
# Trimming dates and time " 20-01-2013 12.58.1 " --> "20-01-2013 12.59.32"
$startdate =~ s/^\s+|\s+$//g;
$enddate =~ s/^\s+|\s+$//g;
$format=~ s/^\s+|\s+$//g;
($startdate, $startdate_time) = split(/ +/, $startdate);
($enddate, $enddate_time) = split(/ +/, $enddate);
$startdate = validateDateFormat($startdate,$format);
if($startdate eq "false"){
return "false"; # invalid date difference
$enddate = validateDateFormat($enddate,$format);
if($enddate eq "false"){
return "false"; # invalid date difference
#converting into YYYYMMDD format
if($enddate == $startdate ){

if(isvalidtime($startdate_time) eq "false"){
print "reached";
return "false";
if(isvalidtime($enddate_time) eq "false"){
print "reached";
return "false";
$startdate_time =~ s/://g;
$enddate_time =~ s/://g;
if($startdate_time < $enddate_time){ return "true"; # Valid date difference }else{ return "false"; # invalid date difference } } elsif($enddate > $startdate ){
return "true"; # Valid date difference
return "false"; # invalid date difference
print 'validateDateDifference("12.12.2013 12:12:58","12.12.2013 12:12:59","ddmmyyyy")\t'.validateDateDifference("12.12.2013 12:12:58","12.12.2013 12:12:59","ddmmyyyy")."\n";
print 'validateDateDifference("12.12.2014 12:12:58","12.12.2014 12:12:12","ddmmyyyy")\t'.validateDateDifference("12.12.2014 12:12:58","12.12.2014 12:12:12","ddmmyyyy")."\n";
print 'validateDateDifference("12.12.2013 12:12:58","12.12.2013 12:12:59","mmddyyyy")\t'.validateDateDifference("12.12.2013 12:12:58","12.12.2013 12:12:59","mmddyyyy")."\n";
print 'validateDateDifference("12.12.2013 12:12:58","12.12.2013 12:12:59","mmmmyyyy")\t'.validateDateDifference("12.12.2013 12:12:58","12.12.2013 12:12:59","mmmmyyyy")."\n";
print 'validateDateDifference("2013-01-31 12:12:58","2013-12-02 12:12:59","yyyymmdd")\t'.validateDateDifference("2013-01-31 12:12:58","2013-12-02 12:12:59","yyyymmdd")."\n";
print 'validateDateDifference("2013-01-31 12:12:58","2013-12-02 12:12:59","yyyymmdd")\t'.validateDateDifference("2013-01-31 12:12:58","2013-12-02 12:12:59","yyyymmdd")."\n";

connecting to archive.ubuntu.com takes too long

I have a Ubuntu 13.04 that I just installed fresh. Now if I try to do anything with apt-get, it tries to connect to archive.ubuntu.com .. It stays at [Connecting to archive.ubuntu.com (2001:67c:1360:8c01::1a)] phase for like 2 minutes, after which it actually starts to communicate and download stuff …

Eventually it always connects, but in waits at the [Connecting to archive.ubuntu.com (2001:67c:1360:8c01::1a)] phase everytime for like 2 minutes !

I didn’t have this problem previously on Ubuntu 13.04, right after reinstalling the OS ..


I figured out the problem. Posted below as an answer!

Running the following command in Terminal tells if IPv6 is enabled or not:

cat /proc/sys/net/ipv6/conf/all/disable_ipv6

0 means its enabled, while 1 means its disabled.

To disable IPv6 from within Terminal, enter the following and reboot:

echo "#disable ipv6" | sudo tee -a /etc/sysctl.conf
echo "net.ipv6.conf.all.disable_ipv6 = 1" | sudo tee -a /etc/sysctl.conf
echo "net.ipv6.conf.default.disable_ipv6 = 1" | sudo tee -a /etc/sysctl.conf
echo "net.ipv6.conf.lo.disable_ipv6 = 1" | sudo tee -a /etc/sysctl.conf

After boot, re-run the first command, and it should be 1 now, after running this run

sudo sysctl -p

all output should be 1, now ipv6 is disable here.

Can’t find a usable init.tcl in the following directories

sometimes while installing ns2  this error “application-specific initialization failed: Can’t find a usable init.tcl in the following directories: ” sucks , we don’t know what to do.

I have a solution.

application-specific initialization failed: Can’t find a usable init.tcl in the following directories:/root/ns2/ns-allinone-2.34/lib/tcl8.4 /usr/local/lib/tcl8.4 /usr/lib/tcl8.4 /usr/local/library /usr/library /usr/tcl8.4.18/library /tcl8.4.18/library /root/ns2/ns-allinone-2.34/lib/tcl8.4

or at local folder too 

There are some solution please try may be they can help:

Solution 1:
1) Go to location root-usr-local-bin by giving following command in terminal
cd /usr/local/bin
2) There you would find the ns file. We just need to remove it by giving following command
rm ns
3) Thats it, you are done. Now your ns starts running successfully.

Solution 2:

 This error can happen if you make any changes to the “ns-allinone-2.34/” directory :
Renaming the directory, moving the directory to another location,
i.e. anything that will change the “/home/arungupta2008/ns-allinone-2.34/tcl8.4.18/lib/” path.
Or when changes were made in /home/arungupta2008/ns-allinone-2.34/tcl8.4.18/lib/
Note : 
The binary ‘ns’ is hard coded to know the location of it’s libraries, tclsh8* :
/home/arungupta2008/ns-allinone-2.34/tcl8.4.18/bin/, /home/arungupta2008/ns-allinone-2.34/tcl8.4.18/lib/

Workarounds, fixes : 
1) cd ns-allinone-2.34/tcl8.4.18/ && ln -s lib/ library
2) Reinstall ns-allinone-2.34  2. The problem is because, ns executable is also at /usr which is conflicting.


Note : while removing symlinks first make that file removable then , you can remove that file  for Ex.     chmod 755 ns

How to recover your blog password

Hello , Friends

i have a website which is hosted be wordpress  , i updated my wordpress from 3.5 to newer version but from that time i was not able to access the my wp-admin menu .

i googled a little bit then i didn’t get any thing then  i tricked with my website ……

1. i downloaded everything from my hosting place to my computer through filezila

2. the i made some changes in files  “admin.functions.php” in “upgrade-functions.php”  .

changes was i added


Put in your own new password for the main admin user. The “1” is the user ID number in the wp_users table.

3. Upload the modified file back to your site.

4. After you then are able to login, make sure to go back and remove that code. It will reset your password on every page load until you do.


Cheers !!!