MayurS Blog

Cron Tab

2010-02-12T07:53:00.000-08:00

his cron tutorial is divided into these subheadings for you to follow it easily:
• What is cron?
• What is cron tab?
• What cron will do for you?
• Have your web server cron enabled?
• What are the components of cron?
• Examples on how to set up cron
• Setting up the cron
o METHOD ONE: Using Cron tab manager
o METHOD TWO: Uploading ‘cron.txt’ file and checking using telnet
 Telnet commands
 Telnet steps (Four steps)
• Cron emails you everytime it runs. How to stop it?
• TIPS in setting up your cron jobs

What is cron?
Actually it is called ‘cron daemon’. Cron is an automatic task machine. You will use it on your Unix or Linux operating systems for doing some tasks at specific intervals with out your intervention every time. You set the clock and forget. The cron daemon runs the work for you.
What is cron tab?
‘Cron tab(CRON TABle)’ is a text file that contains a series of cron functions.
What cron job will do for you?
* If you want to send your email cources to your subscribers at 11.30 night, you will set the cron job on your server. And your cron manager sends one email every day at 11.30 until all the emails will be finished. If you want to send them on Sundays, you can schedule it with your cron.
* You can schedule it to delete your website members with expired accounts.
* You can schedule it to recieve an update on your subscribers from your mailing list manager.
* You can check your links on other websites in link exchange programms.
Have your web server cron enabled?

Have you seen any icon with a name ‘Cron Jobs’ in your control panel?
Have you seen a text link like ‘Cron Manager’ or ‘Cron jobs’?
If you see one, then you are cron enabled. Ask your host about your cron availability. Some host allows cron with out graphical interface. You have to access it through telnet. If you are hosted on Virtual hosting domains then your system administrator has to set up your cron tabs for you.
What are the components of cron?

1: Path to your php or cgi script
2: minutes (Value is 00 – 59. exact minute the cron executes)
3: hour (Value is 00 – 23. hour of the day the cron executes. 0 means midnight)
4: month (Value is 01 – 12. month of the year the cron executes)
5: day (Value is 01 – 31. day of the month the cron executes)
6: weekday (Value is 00 – 06. day of the week the cron executes. Sunday=0,Monday=1…)
Examples on how to set up cron:
If you have installed a php script in your public_html/www/html directory called members.php.
If you want to run this file each night at 11.30 PM every day:

30 23 * * * /home/username/www/members.php
30 – represents the minute of cron work
23 – represents the hour of the day
The * represent every day, month, and weekday.
If you want to set the cron job every sunday at midnight 11.30 PM:

30 23 * * 0 /home/username/www/members.php
0 – represents the Sunday.
If you want the cron job to run at 1:00 and 2:00 A.M:

* 1,2 * * * /home/username/www/members.php
This runs your cron at 1A.M and 2A.M every day, every month and every week.
If you want to run the above task only from Monday to Friday and at 11.30 P.M:
30 23 * * 1-5 /home/username/www/members.php
This runs your cron from Monday to Friday and everyday at 11.30 PM.
Setting up the cron:
• METHOD ONE: Using Cron tab manager
If you have a cron tab manager in your webpanel, it will be easy for you to set the cron tab function. You can click on the icon to open cron manager. There will be some textarea where you can enter the the script file path that you want the cron job to executes.
Your cron manager may be different from the above image, but basically it is easy to set up cron job with your cron manager. I highly recommend this unless you want to get to know about the Second Telnet Method.
• METHOD TWO: Uploading ‘cron.txt’ file and checking using telnet
* Cron Commands:
crontab filename Install filename as your crontab file
crontab -e Edit your crontab file, or create one if it doesn’t already exist.
crontab -l Display your crontab file.
crontab -r Remove your crontab file.
crontab -v Display the last time you edited your crontab file.

* Telnet Steps:
Basically FOUR steps:
1. Create cron.txt
2. Upload
3. Install the txt file as cron file with the command ‘crontab cron.txt’
4. Check your cron file
1. Open your notepad on your computer and write cron job following the guidelines explained above under ‘What are the components of cron?’.
For example – If you write your cron job like this:
30 23 * * * /home/username/www/members.php
After writing the above cron job PRESS return key so that a blank line will be there below the cron job line.
2. Always use absolute path for the command line. Turn off the ‘Word Wrap’ feature with the Notepad.
3. Save the file as ‘cron.txt’. Upload it to your root directory (’/') where you will see a list of folders like public_html,public_ftp,email etc,. Or ask your web host where to upload the cron files. Upload in ASCII mode.

When you ftp into your site, first you will land on your root directory.
4. Now telnet into your server.
5. You have to use telnet software like putty to login into your server.

At command prompt type -
crontab cron.txt
Press Enter.
You will be back at command prompt.
Then type: (l means lowercase L)
crontab -l
Press Enter.
You will see the list of cron jobs that you have entered in cron.txt.
That’s it!!
Cron emails you everytime it runs. How to stop it?
Add this tag at the end of your cron job:
>/dev/null 2>&1
Taking the above example your cron job looks like:
30 23 * * * /home/username/www/members.php>/dev/null 2>&1
TIPS in setting up your cron jobs:
* Ask your host about the procedure if you are not sure of a thing.
* Check your cron once in a while. For example you set your cron to send your ezine at 11.30 PM. Then you subscribe yourself to see it is working or not.
* Upload cron.txt in ASCII mode.
* If you are setting the script path in your schedule, the path SHOULD be from your hosts server root. NOT your domain path.
Ex:/home/user/www/scriptname.php
is correct.
http://www.yourdomain.com/scriptname.php
is incorrect.
* Script names are case sensitive on Unix. So be careful in entering the script name.
* If you are creating cron.txt file and uploading, you should not allow spaces within 1-5 components except between them. (For example 10,30 * * * * is correct not 10 ,30 * * * *)

JavaScript Style Attributes

2010-02-12T07:30:00.000-08:00

JavaScript Style Attributes

Listed below are the tables of CSS properties for various HTML element style attributes. I have added a column indicating the javaScript name that the browser recognizes for these properties. I have only listed those that I know work, but the trend seems to be to use the same name when one name is the style descriptor. When there are two names, use the first name in lower case and the first character of the second name in upper case. Examples:

color = color
background-color = backgroundColor
font-style = fontStyle
font-weight = fontWeight

Box Properties

Name	JavaScript Name	Description	Possible Values	Element Types	Example	inherited
border		Sets border width, style and color.	See border width, style, and color	All	{border: medium solid green}	No
border-bottom		Set the bottom border width style, and color.	See border width, style, and color	All	{border-bottom: medium solid green}	No
border-bottom-width		Set the bottom border width	thin, medium, thick, or length value	All	{border-bottom-width: thin}	No
border-color		Set the border color	A color value, color, #RRGGBB	All	{border: #0000ff}	No
border-left		Set the left border width style, and color.	See border width, style, and color	All	{border-left: medium solid green}	No
border-left-width		Set the left border width	thin, medium, thick, or length value	All	{border-left-width: thin}	No
border-right		Set the right border width style, and color.	See border width, style, and color	All	{border-right: medium solid green}	No
border-right-width		Set the right border width	thin, medium, thick, or length value	All	{border-right-width: thin}	No
border-style		Sets border style	none, dotted, dashed, solid, double, groove, ridge, inset, outset	All	{border: dashed}	No
border-top		Set the top border width style, and color.	See border width, style, and color	All	{border-top: medium solid green}	No
border-top-width		Set the top border width	thin, medium, thick, or length value	All	{border-top-width: thin}	No
border-width		Sets Border width.	thin, medium, thick, or length value	All	{border-width: 8}	No
clear		Determines where floating elements are allowed.	none, left, right, both	All	{clear: left}	No
float		Specifies how text is wrapped and where it is aligned.	none, left, right	All	{float: left}	No
height		Height of element	auto or a height value	Block elements and IMG, INPUT, TEXTAREA, SELECT, and OBJECT	{height: 200}	No
margin		Set element margin width. A single value sets all margins, two values set top and bottom, four values set top, right, bottom, and left margins.	auto, length value, or percent value	All	{margin: 4em 2em 4em 2em}	No
margin-bottom	marginBottom	Set element bottom margin	length value, or percent value	All	{margin-bottom: 4em}	No
margin-left	marginLeft	Set element left margin	length value, or percent value	All	{margin-left: 4em}	No
margin-right	marginRight	Set element right margin	length value, or percent value	All	{margin-right: 4em}	No
margin-top	marginTop	Set element top margin	length value, or percent value	All	{margin-top: 4em}	No
padding		Space between border and content. A single value sets all sides, two values set top/bottom and left/right, three values set top, right/left, and bottom, and four values set top, right, bottom, and left.	length value, or percent value	All	{padding: 4em}	No
padding-bottom		Space between bottom border and content.	length value, or percent value	All	{padding-bottom: 4em}	No
padding-left		Space between left border and content.	length value, or percent value	All	{padding-left: 4em}	No
padding-right		Space between right border and content.	length value, or percent value	All	{padding-right: 4em}	No
padding-top		Space between top border and content.	length value, or percent value	All	{padding-top: 4em}	No
width		Width of element	auto or a height value in length or percentage	Block elements and IMG, INPUT, TEXTAREA, SELECT, and OBJECT	{width: 40em}	No

Gone are the days

2009-11-21T04:20:00.000-08:00

Gone are the days!!!

When
The school reopened in June,
And we settled in our new desks and
benches!
When we queued up in book depot,

And got our new books and notes!

When we wanted two Sundays and no Mondays ,
Yet managed to line up daily for the morning prayers.
We learnt writing with slates and pencils, and
Progressed To fountain pens and ball pens and then Micro tips!
When we began drawing with crayons and evolved to
Color pencils and finally sketch pens!
When we started calculating
first with tables and then with
Clarke's tables and advanced to
Calculators and computers!

When we chased one another in the
corridors in Intervals , and returned to the classrooms
Drenched in sweat!

When we had lunch in classrooms, corridors,
Playgrounds,
under the trees and even in cycle sheds!

When all the colors in the world ,
Decorated the campus on the Second Saturdays!

When a single P.T. period in the week's Time Table,
Was awaited more eagerly than the monsoons!
When cricket was played with writing pads as bats ,
And Neckties and socks rolled into balls!
When few played
"kabadi" and "Kho-Kho" in scorching sun,
While others simply played
"book cricket" in the

Confines of classroom!
Of fights but no conspiracies,
Of Competitions but seldom jealousy!
When we used to
watch Live Cricket telecast,
In the opposite house in Intervals and Lunch breaks!

When few rushed at 3:45 to
"Conquer" window seats in our School bus!
While few others had "Big Fun", "peppermint" ,
"kulfi", " milk ice !" and "sharbat !" at 4o Clock!
Gone are the days

Of Sports Day,
and the annual School Day ,
And the one-month long
preparations for them.

Gone are the days
Of the stressful Quarterly,

Half Yearly and Annual Exams , And the most
enjoyed holidays after them!
Gone are the days
Of tenth and twelfth standards, when
We Spent almost the whole year writing revision tests!
We learnt,
We enjoyed ,
We played,
We won,
We lost,
We laughed,
We cried,
We fought,
We thought.
With so much fun in them, so many friends,
So much experience, all this and more!
Gone are the days
When we used
to talk for hours with our friends!
Now we don't have time to say a 'Hi'!

Gone are the days
When we played games on the road!
Now we
Code on the road with laptop!

Gone are the days
When we saw stars
Shining at Night!
Now we see stars when our code doesn't
Work!
Gone are the days
When we sat to chat with Friends on grounds!
Now we chat in chat rooms.....!
Gone are the days
Where we
studied just to pass!

Now we study to save our job!
Gone are the days
Where we had no money in our pockets and still fun filled on our hearts!!
Now we have the atm as well as credit card but with an empty heart !!

Gone are the days
Where we shouted on the road!
Now we don't shout even at home
Gone are the days
Where we got lectures from all!
Now we give lectures to all... like the one I'm doing now ....!!
Gone are the days
But not the memories, which will be
Lingering in our hearts for ever and ever and
Ever and ever and ever .....

Gone are the Days...... But still there are lot more Days to come in our Life!!
NO MATTER HOW BUSY YOU ARE ,
DONT FORGET TO

LIVE THE LIFE THAT STILL
EXISTS..... :)

New (शिवाजी महाराज असते तर)

2009-11-19T06:09:00.000-08:00

एकदा वाचून बगा

शिवाजी महाराज असते तर

एकदा महाराज मला भेटले,

झोपेत पाहून जोरात कडादले,

"अरे मावल्या झोपतोस काय?,

कोम्ब्डा अरवला ऐकू येत नाही काय?",

"महाराज हयात दोष माझा नाय ,

थंड AC आणि गजराच्या युगात,

कोम्ब्डया च महत्व तरी काय?"

महाराज हसले अणि म्हणाले ,

"चल भवानी मातेच दर्शन घेउया,

ह्या युगातला महाराष्ट्र पाहुया"

दर्शन घेउनी महाराजांनी सर्व किल्ले पाहिले,

शेवटी राजगडअ वर येउनी स्तब्ध राहिले,

म्हणाले,"काय रे दशा झाली या किल्ल्यांची आज?

ज्यांना पाहुनी डगमगले होते पातशाही ताज!!!

मी म्हणालो ,"महाराज, अहो इथे इतिहास आठवतो तरी कुणाला आज?

रेव्ह पार्ट्या करतांना ह्या लोकांना वाटत नाही लाज...!

महाराज विचलित झाले,

म्हणाले,"चल येथून जाऊ यात ,

महाराष्ट्राची राजधानी पहुयात",

महाराजान्सोबत मुंबईत आलो,

तिथल्या झगमगाटआत पूर्णपणे हरवलो,

मुंबई बघता बघता २६/११ च प्रसंग ऐकविला,

तळपायाची आग मस्तकाला गेलेल्या महाराजांनी मलाच प्रश्न केला,

"तुम्ही त्या नाराधामाला जित्ता कैसा सोडिला?"

उत्त्तर काय देणार माझाच चेहरा पडला ,

म्हणालो महाराज ,"तो पहा तो कसब त्यानेच हा प्रसंग घडविला,

पण आजच्या लोकशाहीत न्याय आहे प्रत्येकाला नाही तो फक्त माणुसकीला ....!

वरून आमचेच नेते म्हणती,तुमचेच लोक फितूर ,

बलिदान गेले वाया , मरणयास होते आतुर...!!

महाराज काही बोलले नाहित,

सारख काही तरी विचार करीत राहित,

चालता चालता महाराजांना एक दृश्य दिसल ,

एक इसमास ४-५ जणांनी मरला,

महाराजानी हे हेरल,

ऐसे काय त्याने केल?

म्हणालो ,"महाराज, तो 'भैय्या',परप्रांतीय ,

म्हणुनच त्यासी धरिल...!

यंदा मात्र प्रश्न पडला महाराजन्नाच,

कवी भूषण अणि कलश यांचा विसर पडला माझ्या रयतेलाच?

फिरता फिरता समुद्र किनारी आलो,

महाराजांच्या पुतल्याची कल्पना करुनच प्रफुल्लित झालो,

महाराजांना म्हणालो,

"महाराज,तुमच्या पुतल्याच्या उभारनी साथी उभा आहे तुमचा एक पाईक,

परन्तु तयासी विरोध करिति आपलेच सरनाईक",

महाराज चमकले,

म्हणालो "महाराज,कोणास म्हणावे आपुले अणि कोणास परके,

तुमच्या नावाने येथे जातीचे राजकारण जाहले...!!!!"

महाराजांना जे समजायचा ते ,ते समजले,

अणि परत हसले....

शेवटी मला फक्त एवढच म्हणाले ,

"हे दिवस पाहण्यासाठी का केलि होती आम्ही रचना स्वराज्याची?

त्यासी जोड़ होती १८ पगड जातींची...,

आज हिन्दुस्तानत परत गरज आहे त्या मावल्यांची,

उठ मावल्या उठ हाक आहे ही मातीची......!!!!!!!!

उठ उठ म्हणताच मला जाग आली,

खरच का माझी आणि महाराजांची भेट झाली?

मन महाराजांच्या विचारत गुंतून होते गेले,

पण खरच एकदा महाराज होते मला भेटले....!!!!!

जय भवानी..!!!

जय शिवाजी...!!!

कलियुगातील गोष्ट

2009-08-08T04:29:00.000-07:00

प्रामाणिक (ला)कोड तोड्या

कलियुगातील गोष्ट आहे.

एका गावात दोन (ला)कोड तोडे म्हणजेच साहेबी भाषेत Software Engineers राहत होते. पोटाची खळगी भरण्यासाठी दोघेही कोडिंग करायचे. त्यांतील एक कोड तोड्या प्रामाणिक होता तर दुसरा लबाड होता. सकाळी उठायचे, न्याहरी करून ऑफिस मधे जायचे, Source Tree वर चढून कोड तोडायचे (cut copy paste), दुपारच्याला सब वे मधून बांधून आणलेले फुट लॉंग खायचे, अंमळ विश्रांती घ्यायची, आणि मग उशिरापर्यंत राब राब राबून अंधार पडला की घरी परतायचे असा त्यांचा दिनक्रम असे.

एके दिवशी काय झाले, प्रामाणिक कोड तोड्याचे कामात मन लागत नव्हते. म्हणून आपल्या खुराड्या(cube) मधे बसून कोड तोडण्या ऐवजी तो ऑफिसच्या आवारातल्या पोहण्याच्या तलावापाशी जाऊन बसला. तलावाकाठी बसून लॅपटॉप घेऊन कोड तोडू लागला. बघता बघता त्याला जराशी डुलकी लागली आणि त्याचा लॅपटॉप तलावात पडला. प्रामाणिक कोड तोड्याला खडबडून जाग आली आणि लॅपटॉप पाण्यात पडलेला पाहून तो रडू लागला. त्याला रडताना पाहून एक जलदेवता पाण्यातून बाहेर आली आणि तिने कोड तोड्याला विचारले,

"कोड तोड्या, तू का बरे रडत आहेस ?"

कोड तोड्याने रडत रडत तिला सांगितले

"माझा लॅपटॉप कोड तोडता तोडता पाण्यात पडला. माझ्याकडे दुसरा लॅपटॉप नाही. माझी उद्या डेडलाईन आहे. ती पूर्ण झाली नाही तर माझे कसे होणार ? घरी म्हातारे आई वडील आहेत. त्यांचे कसे होणार ?"

जलदेवता म्हणाली, "रडू नकोस. मी तुझा लॅपटॉप पाण्यातून बाहेर काढून देते."

इतके म्हणून जलदेवतेने पाण्यात बुडी मारली आणि ती एक लॅपटॉप घेऊन बाहेर आली. कोड तोड्याने कन्फिगरेशन पाहिले. हा लॅपटॉप 4 GB RAM चा होता. प्रामाणिक कोड तोड्या म्हणाला,

"हा लॅपटॉप माझा नव्हे. माझा लॅपटॉप तर 1 GB RAM चा होता."

जलदेवतेने पाण्यात पुन्हा बुडी मारली आणि ती अजून एक लॅपटॉप घेऊन बाहेर आली. कोड तोड्याने कन्फिगरेशन पाहिले. हा लॅपटॉप 2 GB RAM चा होता. प्रामाणिक कोड तोड्या म्हणाला,

"हा लॅपटॉप माझा नव्हे. माझा लॅपटॉप तर 1 GB RAM चा होता."

जलदेवतेने पाण्यात तिस-यांदा बुडी मारली आणि ती एक लॅपटॉप घेऊन बाहेर आली. कोड तोड्याने कन्फिगरेशन पाहिले. हा लॅपटॉप 1 GB RAM चा होता. प्रामाणिक कोड तोड्या म्हणाला,

"हाच माझा लॅपटॉप !!"

जलदेवता कोड तोड्याच्या प्रामाणिकपणावर खूश झाली आणि तिने ते तीनही लॅपटॉप प्रामाणिक कोड तोड्याला बक्षीस देऊन टाकले.

दुस-या दिवशी प्रामाणिक कोड तोड्याच्या मित्राने त्याच्याकडे नवीन लॅपटॉप पाहिला. त्याने विचारले, "मित्रा, या इकॉनॉमी मधे तुझ्याकडे नवीन लॅपटॉप कुठून आला ?" प्रामाणिक कोड तोड्याने त्याला जलदेवतेबद्दल सांगितले. ते ऐकून लबाड कोड तोड्याच्या मनात लोभ निर्माण झाला.

दुस-या दिवशी लबाड कोड तोड्या पोहण्याच्या तलावापाशी जाऊन बसला. तलावाकाठी बसून लॅपटॉप घेऊन कोड तोडू लागला. थोड्या वेळाने त्याने आपला लॅपटॉप मुद्दाम तलावात टाकला आणि मोठ्याने रडू लागला. त्याला रडताना पाहून जलदेवता पाण्यातून बाहेर आली आणि तिने कोड तोड्याला विचारले,

"कोड तोड्या, तू का बरे रडत आहेस ?"

कोड तोड्याने रडत रडत तिला सांगितले,

"माझा लॅपटॉप कोड तोडता तोडता पाण्यात पडला. माझ्याकडे दुसरा लॅपटॉप नाही. माझी उद्या डेडलाईन आहे. ती पूर्ण झाली नाही तर माझे कसे होणार ? घरी म्हातारे आई वडील आणि बायका पोरे - नाही नाही - बायको आणि पोरे आहेत. त्यांचे कसे होणार ?"

जलदेवता म्हणाली,

"रडू नकोस. मी तुझा लॅपटॉप पाण्यातून बाहेर काढून देते."

इतके म्हणून जलदेवतेने पाण्यात बुडी मारली. या खेपेस थोडे Optimization करून ती तीन लॅपटॉप घेऊन बाहेर आली आणि कोड तोड्याला विचारले,

"यातला कोणता लॅपटॉप तुझा होता ?"

लबाड कोड तोड्याने कन्फिगरेशन्स पाहिली. तो म्हणाला,

"माझा लॅपटॉप 4 GB RAM चा होता."

जलदेवतेला लबाड कोड तोड्याचा खोटेपणा आवडला नाही आणि ती लबाड कोड तोड्याला कोणताच लॅपटॉप न देता अदृश्य झाली.

कलियुगाचा महिमा :

प्रामाणिक कोड तोड्या तीन लॅपटॉप घेऊन आयुष्यभर कोडिंगच करत राहिला.

लबाड कोड तोड्याचा लॅपटॉप पाण्यात पडल्याने त्याला कोड लिहिता येईना. मग कंपनीने त्याला मॅनेजर बनवून नवीन ब्लॅकबेरी घेऊन दिला

Words Lyrics Its Awesome

2009-04-22T02:25:00.000-07:00

$mile an ever lasting smile
a smile can bring you near to me
don't ever let me find you gone
'cause that would bring a tear to me
this world has lost its glory
let's start a brand new story
now my love
you think that I don't even mean
a single word I say

it's only words
and words are all I have
to take your heart away

talk in ever lasting words
and dedicate them all to me
and I will give you all my life
i'm here if you should call to me
you think that I don't even mean
a single word I say

it's only words
and words are all I have
to take your heart away

it's only words
and words are all I have
to take your heart away

da da da da da da da
da da da da da da da da da da
da da da da da da da
da da da da da da da da da da

this world has lost its glory
let's start a brand new story
now my love
you think that I don't even mean
a single word I say

it's only words
and words are all I have
to take your heart away

it's only words
and words are all I have
to take your heart away

it's only words
and words are all I have
to take your #eart away

Regular Expression

2008-11-20T06:20:00.001-08:00

What is a Regular Expression?

A regular expression is a set of characters that specify a pattern. Regular expressions are used when you want to search for specify lines of text containing a particular pattern. Most of the UNIX utilities operate on ASCII files a line at a time. Regular expressions search for patterns on a single line, and not for patterns that start on one line and end on another.

It is simple to search for a specific word or string of characters. Almost every editor on every computer system can do this. Regular expressions are more powerful and flexible. You can search for words of a certain size. You can search for a word with four or more vowels that end with an "s." Numbers, punctuation characters, you name it, a regular expression can find it. What happens once the program you are using find it is another matter. Some just search for the pattern. Others print out the line containing the pattern. Editors can replace the string with a new pattern.

Parts Of Regular Expression

There are three important parts to a regular expression.

1) Anchors are used to specify the position of the pattern in relation to a line of text.

2) Character Sets match one or more characters in a single position.

3) Modifiers specify how many times the previous character set is repeated.

A simple example that demonstrates all three parts is the regular expression "^#*."

The up arrow is an anchor that indicates the beginning of the line. The character "#" is a simple character set that matches the single character "#." The asterisk is a modifier.

The Anchor Characters: ^ and $

Pattern	Matches
^A	"A" at the beginning of a line
A$	"A" at the end of a line
A^	"A^" anywhere on a line
$A	"$A" anywhere on a line
^^	"^" at the beginning of a line
$$	"$" at the end of a line

The use of "^" and "$" as indicators of the beginning or end of a line is a convention

Matching a character with a character set :

The simplest character set is a character. The regular expression "may" contains three character sets: "m," "a" and "y." It will match any line with the string "may" inside it. This would also match the word "mayur." To prevent this, put spaces before and after the pattern: " may ."

Match any character with . (DOT)

The character "." is one of those special meta-characters. By itself it will match any character, except the end-of-line character. The pattern that will match a line with a single characters is ^.$

Specifying a Range of Characters with [...]

If you want to match specific characters, you can use the square brackets to identify the exact characters you are searching for. The pattern that will match any line of text that contains exactly one number is

^[0123456789]$

. You can also use the hyphen between two characters to specify a range:

^[0-9]$

You can also have explicit characters with character ranges. This pattern will match a single character that is a letter, number, or underscore:

[A-Za-z0-9_]

Rules in Short.

Regular Expression	Class	Type	Meaning
_
.	all	Character Set	A single character (except newline)
^	all	Anchor	Beginning of line
$	all	Anchor	End of line
[...]	all	Character Set	Range of characters
*	all	Modifier	zero or more duplicates
\<	Basic	Anchor	Beginning of word
\>	Basic	Anchor	End of word
$..$	Basic	Backreference	Remembers pattern
\1..\9	Basic	Reference	Recalls pattern
_+	Extended	Modifier	One or more duplicates
?	Extended	Modifier	Zero or one duplicate
\{M,N\}	Extended	Modifier	M to N Duplicates
(...\|...)	Extended	Anchor	Shows alteration