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sangkrit
This site is for learning dominant web technologies only so if you have any query for improving your technical knowledge in this regard you are most welcome here but please be careful for not writing anything out of subject. Although you may comfortably discuss the expected fall of iron prices also by creating a new website on the platform of sangkrit.net
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p2p
Managing File Systems
An introduction to Linux file system is ‘here‘.
If you want to reformat the flash drive with a Linux native file system, rather than the FAT32 system. It involves two steps. First create a new partition layout if the existing one is not to our liking, and second create a new, empty file system on the drive.
Handling Partitions With fdisk: The fdisk program allows us to interact directly with disk-like devices (such as hard disk drives and flash drives) at a very low level. With this tool we can edit, delete, and create partitions on the device. To work with our flash drive, we must first unmount it (if needed) and then invoke the fdisk program as follows:
[linux@ubuntu ~]$ sudo umount /dev/sdb1
[linux2@ubuntu ~]$ sudo fdisk /dev/sdb
Notice that we must specify the device in terms of the entire device, not by partition number. After the program starts up, we will see the following prompt:
Command (m for help):
(Entering an “m” will display the program menu as follows:)
Command action
a toggle a bootable flag
b edit bsd disklabel.
c toggle the dos compatibility flag.
d delete a partition
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition’s system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality
Test and repair: Each time the system boots, it routinely checks the integrity of the file systems before mounting them. This is done by the fsck program (short for “file system check”). The last number in each fstab entry defines the order the devices are to be checked. The root file system is checked first, followed by the home and boot file systems. Devices with a zero as the last digit are not routinely checked.
In addition to checking the integrity of file systems, fsck can also repair corrupt file systems with varying degrees of success, depending on the amount of damage. On Unix like file systems, recovered portions of files are placed in the lost+found directory, located in the root of each file system.
To check our flash drive we could do the following:
[linux@ubuntu ~]$ sudo fsck /dev/sdb1
fsck 1.40.8 (19-Apr-2011)
e2fsck 1.40.8 (19-Apr-2011)
/dev/sdb1: clean, 11/3904 files, 1661/15608 blocks
Mostly, file system corruption is quite uncommon unless there is a hardware trouble, such as a failing disk drive. On most systems, file system corruption detected at boot time will cause the system to stop and direct you to run fsck before continuing.
“In Unix society, the word “fsck” is often utilized in spot of a popular word with which it shares three letters. This is especially appropriate, given that you will probably be uttering the aforementioned word if you find yourself in a situation where you are forced to run fsck.” -
p2p
How To Create A Wikipedia Page
Articles in Wikipedia are only created by registered user. So first you need to become a registered user of Wikipedia.
Registering yourself on Wikipedia
Open http://www.wikipedia.org :
Click on ‘log in/ create account’ link on the upper right corner of Wikipedia’s main page:
Click on the link ‘create one’:
Choose username and password and fill in other details and click ‘create account’. Email is not mandatory; it is used only if you forgot your password. So it depends on you that weather you have to add an email to your Wikipedia account or not:
You will be redirected to some other page showing you the message ‘Login Successful’:
Starting to create a new Wikipedia page:
For creating a new Wikipedia page search the title of the page in the search box present on the upper right corner of wikipedia.org to check weather the page is already been created by someone or not and if page is been created earlier then you may start editing or you may redirect your article to that page.
If page is not yet created then you may start creating it. Suppose you want to create a page Open Source Council. Then search for open source council on the wikipedia’s search box, if search results displays line ‘You may create the page’ followed by the name of page ‘Open Source Council’(here) in red.
The page will get open for editing:
Scrolling down the page you will see the buttons:
Save page: This button makes the page will become publicly visible so only use it when your page is ready.
Show preview: Use this button to see the preview of the page before saving it.
Watch this page(checkbox): Checking this box add the page to your watchlist, the pages you want to monitor for changes are listed here.
You may check your watchlist by clicking ‘My watchlist’ present in the upper right corner of wikipedia when you are logged in.Reference/Citation:
This is the most important part of any Wikipedia article. References are the citation to reliable source which proves your article trustworthy.
References are enclosed in <ref> and </ref> .
For example:
An statement in any Wikipedia page____________________________________________________till here. (Start your reference here)
<ref>{{cite web|url=http://example.com |title= Title |publisher= The publisher |date= YY-MM-DD}}</ref> -
p2p
PHP: Access Variables By Using Indirect References
Variables in PHP are preceded with a $ sign, they can start with a letter or _ (underscore) and can then contain as many alphanumeric characters and underscores.
Examples of legal variable names include:
$count
$_Obj
$A123
Example of illegal variable names include
$123
$*ABC
You don’t need to declare variables or their type before using them in PHP. The following code example uses variables:
$PI = 3.14;
$radius = 5;
$circumference = $PI * 2 * $radius; // Circumference = π * d
You can see that none of the variables are declared before they are used. Also, the fact that $PI is a floating-point number, and $radius (an integer) is not declared before they are initialized. PHP does not support global variables like many other programming languages (except for some special pre-defined variables). Variables are local to their scope, and if created in a function, they are only available for the lifetime of the function. Variables that are created in the main script (not within a function) aren’t global variables; you cannot see them inside functions, but you can access them by using a special array $GLOBALS[], using the variable’s name as the string offset. The previous example can be rewritten the following way:
$PI = 3.14;
$radius = 5;
$circumference = $GLOBALS["PI"] * 2 * $GLOBALS["radius"];
➥ // Circumference = π* d
An extremely useful feature of PHP is that you can access variables by using indirect references, or to put it simply, you can create and access variables by name at runtime. Consider the following example:
$name = “name”;
$$name = “Registered user”;
print $name;
This code results in the printing of ” Registered user .” The second line uses an additional $ to access the variable with name specified by the value of $name (“name”) and changing its value to “Registered user”. Therefore, a variable called $name is created. You can use as many levels of indirections as you want by adding extra $ signs in front of a variable -
p2p
Linux: Concatenate Files
The cat command reads one or more files and copies them to standard output:
cat [file...]
You can use it to display files without paging, for example:
[linux@ubuntu ~]$ cat ls-output.txt will display the contents of the file ls-output.txt. cat is often used to display short text files. Since cat can accept more than one file as an argument, it can also be used to join files together. Say we have downloaded a large file that has been split into multiple parts (multimedia files are often split this way on USENET), and we want to join them back together. If the files were named:
movie.mpeg.001 movie.mpeg.002 … movie.mpeg.099
we could join them back together with this command:
cat movie.mpeg.0* > movie.mpeg
Since wildcards always expand in sorted order, the arguments will be arranged in the correct order.
This is all well and good, but what does this have to do with standard input? Nothing yet, but let’s try something else. What happens if we type “cat” with no arguments:
[linux@ubuntu ~]$ cat
Nothing happens, it just sits there like it’s hung. It may seem that way, but it’s really doing exactly what it’s supposed to. If cat is not given any arguments, it reads from standard input and since standard input is, by default, attached to the keyboard, it’s waiting for us to type something! . Like:
[linux@ubuntu ~]$ cat
[Text] -
p2p
Command Line Keyboard Tricks
Other than moving cursor with arrow keys there are much more useful keyboard tricks in Linux command line:
Ctrl-a Move cursor to the beginning of the line.
Ctrl-e Move cursor to the end of the line.
Ctrl-f Move cursor forward one character; same as the right arrow key.
Ctrl-b Move cursor backward one character; same as the left arrow key.
Alt-f Move cursor forward one word.
Alt-b Move cursor backward one word.
Ctrl-l Clear the screen and move the cursor to the top left corner. Its same as ‘clear’ command
Ctrl-d Delete the character at the cursor location
Ctrl-t Transpose (exchange) the character at the cursor location with the one preceding it.
Alt-t Transpose the word at the cursor location with the one preceding it.
Alt-l Convert the characters from the cursor location to the end of the word to lowercase.
Alt-u Convert the characters from the cursor location to the end of the word to uppercase.
Ctrl-k Kill text from the cursor location to the end of line.
Ctrl-u Kill text from the cursor location to the beginning of the line.
Alt-d Kill text from the cursor location to the end of the current word.
Alt- Backspace Kill text from the cursor location to the beginning of the current word. If the cursor is at the beginning of a word, kill the previous word.
clear – Clears the screen
history – Display the history list
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p2p
Linux: Redirection
The “I/O” stands for input/output and with this facility you can redirect the input and output of commands to and from files, as well as connect multiple commands together into powerful command pipelines. To show off this facility, we will introduce the following commands:
● cat – Concatenate files
● sort – Sort lines of text
● uniq – Report or omit repeated lines
● grep – Print lines matching a pattern
● wc – Print newline, word, and byte counts for each file
● head – Output the first part of a file
● tail – Output the last part of a file
● tee – Read from standard input and write to standard output and filesStandard Input, Output, And Error:
Many of the programs that we have used so far produce output of some kind. This output often consists of two types. First, we have the program’s results; that is, the data the program is designed to produce, and second, we have status and error messages that tell us how the program is getting along. If we look at a command like ls, we can see that it displays its results and its error messages on the screen. Keeping with the Unix theme of “everything is a file,” programs such as ls actually send their results to a special file called standard output (often expressed as stdout) and their status messages to another file called standard error (stderr). By default, both standard output and standard error are linked to the screen and not saved into a disk file. In addition, many programs take input from a facility called standard input (stdin) which is, by default, attached to the keyboard. I/O redirection allows us to change where output goes and where input comes from. Normally, output goes to the screen and input comes from the keyboard, but with I/O redirection, we can change that.
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p2p
Linux: How To Create A New File System
If you want to reformat the flash drive with a Linux native file system, rather than the FAT32 system. This involves two steps:
1. Create a new partition layout if the existing one is not to our liking, and
2. Create a new, empty file system on the drive.Handling Partitions With fdisk:
The fdisk program allows us to interact directly with disk-like devices (such as hard disk drives and flash drives) at a very low level. With this tool we can edit, delete, and create partitions on the device. To work with our flash drive, we must first unmount it (if needed) and then invoke the fdisk program as follows:[linux@ubuntu ~]$ sudo umount /dev/sdb1
[linux2@ubuntu ~]$ sudo fdisk /dev/sdbNotice that we must specify the device in terms of the entire device, not by partition number. After the program starts up, we will see the following prompt:
Command (m for help):
(Entering an “m” will display the program menu as follows:)
Command action
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition’s system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality -
p2p
Command’s Manual Page
Most executable programs intended for command line use provide a formal piece of documentation called a manual or man page. A special paging program called man is used to view them. It is used like this:
man name_of_conmmand
here “name_of_conmmand” is the name of the command to view.
Man pages vary somewhat in format but generally contain a title, a synopsis of the command’s syntax, a description of the command’s purpose, and a listing and description of each of the command’s options. Man pages, however, do not usually include examples, and are intended as a reference, not a tutorial. As an example, let’s try viewing the man page for the ls command:
[linux@ubuntu ~]$ man ls
On most Linux systems, man uses less to display the manual page, so all of the familiar less commands work while displaying the page.
The “manual” that man displays is broken into sections and not only covers user commands but also system administration commands, programming interfaces, file formats etc.
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Ashlyn Nicely
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p2p 1:20 AM on January 24, 2012 Permalink |
Add this line: define(‘BP_DISABLE_ADMIN_BAR’, true); to your theme’s function.php file.