Grep Command example in Unix/Linux

Here are some of the frequently used grep command in unix/Linux with examples:

1. Search a given string in a file

grep "search_string" file_name

2. Search a specific string in multiple files by providing the file name pattern

grep "search_string" file_name_pattern

e.g.: grep "name" class*.txt

3. Case insensitive search

grep -i "search_string" file_name

e.g.
Both commands would return same result

grep -i "name" class1.txt
grep -i "NAME" class1.txt

4. Invert match

grep -v "101" class1.txt

Above command would return all the rows that doesn't contain the string "101".

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Useful HTML Codes that can be used while writing articles or blogs

I normally faced problem when writing mathematical operators, functions, symbols etc in my blogs/websites. Then I found that there are lot of HTML codes that can be used to write the symbols. Here is a list of symbols and their HTML Codes for your reference.

Regular Characters that are special in HTML
"  &quot; &#34; {quotation mark}	&  &amp; &#38; {ampersand}	<  &lt; &#60; {less than}	>  &gt; &#62; {greater than}	&nbsp; &#160; {Non-breaking space}

---

Special Punctuation
‘  ‘ ‘ ‘ {left single quote}	’  ’ ’ ’ {right single quote}	…  … … … {ellipsis}
“  “ “ “ {left double quote}	”  ” ” ” {right double quote}	‼  ‼ {double exclamation mark}
‛  ‛ {single backwards right quote}	„  „ „ „ {double comma}	¡  ¡ ¡ {upside-down exclamation mark}
¿  ¿ ¿ {upside-down question mark}

---

Legal Marks
™  ™ ™ ™ {trademark}	©  © © {copyright}	®  ® ® {registered}

---

Currency Symbols
¤  ¤ ¤ {currency}	₹  ₹ {Indian Rupee}	¢  ¢ ¢ {cent}	€  € € € {euro}
£  £ £ {English pound}	₤  ₤	¥  ¥ ¥ {Japanese yen}	₧  ₧{Spanish peseta}

---

Math Symbols
‰  ‰ ‰ ‰ {per mille}	¬  ¬ ¬ {not}	⌐  ⌐	degree °  ° °
¹  ¹ ¹ {exponent one}	²  ² ² {exponent two}	³  ³ ³ {exponent three}	ⁿ  ⁿ {exponent n}
º  º º {exponent zero (or male ordinal)}	ª  ª ª {exponent a (or female ordinal)}	∟  ∟	¯  ¯ ¯ {macron}
×  × × {multiply}	÷  ÷ ÷ {divide}	′  ′ ′ {prime}	″  ″ ″ {double prime}
⁄  ⁄ ⁄ ∕ {fraction slash}	∂  ∂ ∂ {partial differential}	∏  ∏ ∆ {n-ary product}	∑  ∑ ∑ {n-ary summation}
℮  ℮ {Euler's number or Napier's constant}	Ω  Ω {ohm or Omega constant}	∆  ∆ {change}	µ  µ µ {micro (one millionth)}
−  − − {minus}	∙  ∙ {dot product}	√  √ √ {square root}	∞  ∞ ∞ {infinity}
∩  ∩ ∩ {intersection}	∫  ∫ ∫ {integral}	⌠  ⌠ {integral: upper half}	⌡  ⌡ {integral: lower half}
≈  ≈ ≈ {almost equal to}	≠  ≠ ≠ {not equal to}	≡  ≡ ≡ {equivalent}	±  ± ± {plus or minus}
≤  ≤ ≤ {less-than or equal to}	≥  ≥ ≥ {greater-than or equal to}

---

Fractions
¼  ¼ ¼ {one-quarter}	½  ½ ½ {one-half}	¾  ¾ ¾ {three-quarters}	⅓  ⅓ {one-third}
⅕  ⅕ {one-fifth}	⅖  ⅖ {two-fifths}	⅗  ⅗ {three-fifths}	⅘  ⅘ {four-fifths}
⅙  ⅙ {one-sixth}	⅚  ⅚ {five-sixths}	⅔  ⅔ {two-thirds}	⅛  ⅛ {one-eighth}
⅜  ⅜ {three-eighths}	⅝  ⅝ {five-eighths}	⅞  ⅞ {seven-eighths}

---

Playing Card Suits
♠  ♠ ♠ {spade card suit}	♣  ♣ ♣ {club card suit}	♥  ♥ ♥ {heart card suit}	♦  ♦ ♦ {diamond card suit}

---

For many more other html symbols, refer the useful site http://brucejohnson.ca/SpecialCharacters.html ♈♈

How to take Back up of the Registry in Windows

To make any changes to Regestry or take a back up of the Registry, you must login as Administrator. It is always safe and good practice to keep a back up(EXPORT) of the registry before doing any change to it. Later, if you want to revert the changes, you need to just IMPORT the back up registry file.

1. Open the Registry Editor
Click on Start button, then type regedit into the search box, and press Enter.‌  If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
2.Locate and click the key or subkey that you want to back up. If you want a complete backup, click on Computer in registry editor.
3.Click the File menu, and then click Export.
4. Save the back up file
In the Save in box, select the location where you want to save the backup copy to, and then type a name for the backup file in the File name box. Click Save.

awk command in Unix

awk is a very useful and powerful command in Unix. It's used to work with columns in a text file.

Here is a simple awk command to list the data of 1st column in a text file.



awk '{print $1}'   file_name

We can specify the field-separator using -F option. Refer below example.
Here tab is the filed separator. Below command will print the content of Column 2 in text file.
awk -F'\t' '{print $2}' file_name

We can print the length of data in column 2 using below awk command.
awk -F'\t' '{print length($2)}' file_name

We can check conditions in awk command and print accordingly.
awk -F'\t' '{if(length($4) > 50 ) print $4} ' file_name

The above command will print all the data in Column 4 if length of data is greater than 50 characters.

For more Tips & Tricks in Unix, Click Here.

Group by and Count is Microsoft Excel

Sometimes, we may need to group data in a Column in Excel and take the distinct values and the count of their occurrence.

Refer below data.

In the above data, if we need distinct values and the number of occurrences, follow the below steps:

1. First get the distinct values to another column. Refer detailed instructions here.
2. Then, use COUNTIF function to get the count of occurrence.

COUNTIF usage:

COUNTIF takes two parameters, 1st is a range where data is present multiple times, and 2nd is the value whose count needs to be found.

Syntax:

=COUNTIF(A1:A12, B1)

For more Tips & Tricks in Excel, Click Here.

How to get distinct records in Microsoft excel?

Follow the below steps to get distinct values from a column in excel sheet to a blank column.

1. Select Data-Filter-Advanced filter
2. Set your list range to the range containing data whose distinct to be retrieved
3. Check Copy to Another Location
4. Check Unique Records Only
5. Set Copy To range to an empty range on the same worksheet.

For more Tips & Tricks in Excel, Click Here.

How to alter a table in Oracle to modify multiple column definition

Oracle alter multiple columns
----------------

To alter a single column in Oracle, the syntax is as below:

alter table
   table_name
modify
   column_name  datatype;

If you want to modify multiple columns, use below syntax:

alter table
   table_name
modify
   (
   column1_name  column1_datatype,
   column2_name  column2_datatype,
   column3_name  column3_datatype,
   column4_name  column4_datatype
   );

The above command is really helpful and saves time while modifying multiple columns in Oracle.

For more tips and tricks on Oracle, click here.

Oracle sqlldr - how to load first few characters of a string to Database in sqlldr

Today I had a Unique challenge while loading Data from text files to Oracle Database using sqlldr.

Many records were getting discarded as bad records. After investigation, I found that, the data is getting rejected because of a specific column whose length is less compared to the length of data in text file. I was getting error as below:

Error on table tbl_test, column col2.
Field in data file exceeds maximum length

The size and datatype of column col2 is varchar2(100).

To load all the data to the Database without any bad records, there are two options.
1. Increase the column width to match the length of data
OR
2. Truncate the data to 100 chars before loading to DB

I preferred the second option for below reasons:
a) First 100 chars of the string is sufficient for my analytics
b) Less space consumption
c) I am not sure of the maximum length that can be for that column in text file.

Now I am decided to trim the data to first 100 chars before loading to DB.
Let's see how to load first few characters of a string to Database in sqlldr?

We have to modify the ctl file (control file) as below:

Old ctl file:

LOAD DATA
INFILE "INFILE_NAME"
BADFILE "BAD_FILE"
DISCARDFILE "DISCARD_FILE"
APPEND into table tbl_test
fields terminated by '\t'
trailing nullcols
(
col1,
col2,
col3,
col4 sysdate
)

Modified ctl file:

LOAD DATA
INFILE "INFILE_NAME"
BADFILE "BAD_FILE"
DISCARDFILE "DISCARD_FILE"
APPEND into table tbl_test
fields terminated by '\t'
trailing nullcols
(
col1,
col2 CHAR(1000) "substr(:col2,1,100)",
col3,
col4 sysdate
)

Change Details:

1. We are using substring function to load first 100 chars
2. If you don't specify length of the input character data, sqlldr uses default of 255 characters. Hence by explicitly mentioning CHAR(1000), we are instructing sqlldr to read all data where col2 length is less than or equal to 1000 chars. We have to increase this number if we see data having higher length.

For more Oracle Tips, Click here. 

Excel Lookup function - Search a name and show it's vaue

This article will explain what is Lookup function in Microsoft excel and how to use Lookup function with example.

LOOKUP function is a very useful function in Microsoft Excel which returns  a value from a range of values(a row or a column) or from an array.

There are two forms of the function.

1. Vector form
2. Array Form

1. Vector Form
-------------------

In this form, the function searches for the lookup_value in a range, i.e. a row or a column and when a match is found, it takes the corresponding result_value from another range specified (row or column).

Note: The data in lookup_range must be in sorted order. Otherwise Lookup function will give incorrect result.

Syntax:

=LOOKUP(lookup_value, lookup_range,[result_range])

result_range is optional.

Example:

Here are some more examples and the corresponding result:

=LOOKUP(104,A2:A5)              returns 104

=LOOKUP(103,A2:A5,B2:B5)     returns Binay

2. Array Form

The array form, the LOOKUP function searches for the value in the first row or column of the array and returns the corresponding value in the last row or column of the array.

Syntax:

=LOOKUP(lookup_value,array)

Example:

=LOOKUP("B", {"A","B","C","D";10,11,12,13})    returns 11 =LOOKUP("B", {"a","b","c","d";10,11,12,13})   returns 11
=LOOKUP("b", {"A","B","C","D";10,11,12,13})   returns 11
=LOOKUP("E", {"A","B","C","D";10,11,12,13})   returns 13
=LOOKUP("Back", {"A","B","C","D";10,11,12,13})   returns 11
=LOOKUP("0", {"A","B","C","D";10,11,12,13})   returns #N/A

For more Tips & Tricks in Excel, Click Here.

Frequently Used Crontab Commands

Here are few commands used frequently in Crontab:

1. crontab -l
Lists all the entries in Crontab

2. crontab -l | grep script_name
Lists all crontab entries containing the Script_name

3. crontab -e
Opens VI Editor to edit cron entry

To understand Crontab Entry, click here.
More Unix Tips.

Understanding CRON Entry

What are the meanings of parameters on a Cron Entry?

When we schedule a job in the Unix Server, we insert an entry in the CronTab.
A typical Cron Entry will look like below:


* * * * * Command to execute

Below image defines the meaning of each parameter.

 There are several special predefined values which can be used to substitute the CRON expression.

Here are some examples to understand usage of the parameters in Cron entry:

1. Cron script1.ksh to run at 02:10 AM everyday
10 02 * * * script1.ksh

2. Cron script2.ksh to run every hour at the 30th minute
30 * * * * script2.ksh

3. Cron script3.ksh to run twice daily, once at 01:10 and second at 13:10
10 01,13 * * * script3.ksh

4. Cron script4.ksh to run at 0th, 1st, 2nd, 3rd, 4th, 5th minute of each hour
00,01,02,03,04,05 * * * * script4.ksh

5. Cron script5.ksh to run at 4th minute of every 2 hours eg 00:04, 02:04, 04:04, 06:04 etc
04 */2 * * * script5.ksh

The below reference template can be added at the top of a crontab for easy reference.

# .---------------- minute (0 - 59)
# |   .------------- hour (0 - 23)
# |   |   .---------- day of month (1 - 31)
# |   |   |   .------- month (1 - 12) OR jan,feb,mar,apr ...
# |   |   |   |  .----- day of week (0 - 7) (Sunday=0 or 7)  
# |   |   |   |  |       OR sun,mon,tue,wed,thu,fri,sat
# *   *   *   *  *  command to be executed

For more Unix Tips, Click here.

How to compare two strings in excel?

Excel string compare:


There is an inbuilt function called EXACT in excel to compare two strings.
It returns TRUE if both the strings are same, else FALSE.

Usage:
=EXACT(Cell1,Cell2)

Example:

For more Tips & Tricks in Excel, Click Here.

Comment in .ini files

Do standard windows .ini files allow comments?
YES

You can put comments in a .ini file using a Semi-colon(;). See example below:

1. Commenting a portion of a line
Name="ABC" ; Comment
2. Commenting a full line
; This is a line comment

Disk Partition management using Partition Wizard from MiniTool

Problem Faced while extending C Drive:

My hard disk was initially divided into two Partitions, one is C Drive that contains OS and the other one is D Drive for data. As the usage became more, more and more programs got installed making C Drive out of space.

I had enough free space in D Drive. I wanted to reduce the size of D Drive and increase the size of C Drive.

The OS in my machine is Windows 7. It has in built partitioning functions in Computer -> Manage -> Storage -> Disk Management. I used options like Shrink Volume and Extend Volume by right clicking on the different drives.

But, I could not extend C Drive by using the space released from D drive.

I thought this might be a common problem faced by many others. That's why I am sharing how I extended C Drive using Partition Wizard from MiniTool.

Problem fixed using Partition Wizard from MiniTool:

After a google search and reading many posts from search results, trying few free softwares, i couldn't find a proper solution for my specific problem. Then I found Partition Wizard from MiniTool. It solved my problem. Thanks to MiniTool team.

Steps to use Partition Wizard from MiniTool:

• Download the free software from Partition Wizard website
• Install it.
• Refer excellent help videos at their help portal.

The second video "2. I can not resize my partitions, Why?" helped me in fixing my problem.

Post your questions/comments. Thank you.

Ultra Low cost tablet AAKASH is now available online for purchase

The much awaited Ultra Low cost tablet AAKASH is now available online for purchase in India. It will be very much useful for students. It will help to access internet and work with documents like word, excel, power point,   pdf files etc. Also, it will support multimedia files like Images, audio files and Video files. Students will be able to watch Youtube videos in the device and learn from video tutorials.

It will cost Rs 2,500. To get your AAKASH Tablet, Order Online at http://www.aakashtablet.com/
You will get the delivery in one week time and you have to pay the cash on delivery.

So, why delay? Book as soon as possible.

How to Link to different sections in an html page

If you want to link to different sections in your HTML webpage, or point to different headers in a HTML document, here is how you can do it.

How to add a link to a section in an HTML page:

<a name="OldPapers">Old Papers Section</a>

We can access the section directly by using below URL:
http://www.websitename.com#OldPapers

Even we can add link to sections by providing ID attribute with a tag.
<h3 id="HeadingSection">Heading Section</h3>
We can access the section directly by using below URL:
http://www.websitename.com#HeadingSection

Here is an example. All bank Exam Blog
All bank Exam Blog Old Papers Section

The Code for second one is <a href="http://allbankexam.blogspot.com/#OldPapers">All bank Exam Blog Old Papers Section</a>

Read more at http://www.w3.org/TR/html401/struct/links.html

How to find the Version of Internet Explorer?

 To find version of your Internet Explorer, go to Help > About Internet Explorer.

Show Desktop icon missing. How to create Show Desktop Icon?

If Show Desktop Icon is missing in your computer, just follow the below steps to create it again.

1. Click Start, click Run, type notepad in the Open box, and then click OK.
2. Copy and then paste the following text into the Notepad window:
Code for Show Desktop Icon:
[Shell]
Command=2
IconFile=explorer.exe,3
[Taskbar]
Command=ToggleDesktop
3. On the File menu, click Save As, and then save the file to your desktop as "Show desktop.scf". The Show desktop icon is created on your desktop and it should look like below image.

4.Click and then drag the Show desktop icon to your Quick Launch toolbar.

Also Read: Show Desktop icon missing in Windows 7

Show Desktop icon missing in Windows 7

When I used Windows 7 initially, I felt that the "Show Desktop" Icon was missing. I was looking for an icon like below which was there in Windows XP or Windows Vista.

Then I realized that Windows 7 also has the Show Desktop icon. But, it is at a different location and in a different shape. Refer below screen shot. Show Desktop Icon at the Extreme Right and Bottom corner of your screen.

Also read:
 Show Desktop icon missing. How to create Show Desktop Icon?

What is PING command in Command Prompt?

Using PING command, we can determine if we can reach a host computer in Internet or not. And also, we can determine how long it takes for a roundtrip (i.e. From Source computer to Destination computer and back to source.)

Definition: PING Command is a very useful Utility to test the reachability of a host on an Internet Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a destination computer.

PING stands for "Packet Inter-Network Groper".

How to Run PING Command?

1. Go to Start -> Run and then type cmd
2. Type ping followed by computer name or IP Address, for example type ping google.com
or type ping 209.85.231.104

If you get result like below image, then the destination computer is up and running and you are able to connect to that .

If you get  result like below image, then the destination computer is either down or not connected to internet or you are not able to connect to that.