Linux Commands Help: grep

Find text in a file:

 For example to find out "404" requests( page not found ) in apache log file:

grep "404" /var/log/apache2/access.log

 The above command displays all the entries contains the word "404".

   

grep -n "404" /var/log/apache2/access.log

The above command displays all the entries contains the word "404" with line numbers.

   

grep -c "404" /var/log/apache2/access.log

The above command displays the no. of entries contains the word "404"

grep -c "404\|192.168.20.32" /var/log/apache2/access.log

The above command displays the no. of entries contains both the words "404" and "192.168.20.32"

Change Time Zone in MySQL

By default, MySQL uses timestamp of server.  

To check this, run 

SELECT @@global.time_zone, @@session.time_zone;

which returns "system";

• Run the following command in terminal to change server timezone:

       sudo dpkg-reconfigure tzdata

         which prompts a dialog to change time zone:

• Now restart mysql server: /etc/init.d/mysql restart

        Run "SELECT NOW();" query in MySQL editor, which should return the   time of modified time zone .

Mysql command line commands - Linux

To login from linux command prompt

#mysql -h hostname -u root -p

Create a database on the sql server

mysql> create database [databasename];

List all databases on the sql server

mysql> show databases;

Switch to a database

mysql> use [db name];

To see all the tables in the db.

mysql> show tables;

To see database's field formats

mysql> describe [table name];

To delete a db

mysql> drop database [database name];

To delete a table

mysql> drop table [table name];

Show all data in a table

mysql> SELECT * FROM [table name];

Returns the columns and column information pertaining to the designated table

mysql> show columns from [table name];

Show certain selected rows with the value "rao"

mysql> SELECT * FROM [table name] WHERE [field name] = "rao";

Show all records containing the name "rao" AND the phone number '98467258'.

mysql> SELECT * FROM [table name] WHERE name = "rao" AND phone_number = '98467258';

Show all records not containing the name "rao" AND the phone number '98467258' order by the phone_number field.

mysql> SELECT * FROM [table name] WHERE name != "rao" AND phone_number = '98467258' order by phone_number;

Show all records starting with the letters 'bob' AND the phone number '3444444'.

mysql> SELECT * FROM [table name] WHERE name like "Bob%" AND phone_number = '3444444';

Show all records starting with the letters 'bob' AND the phone number '3444444' limit to records 1 through 5.

mysql> SELECT * FROM [table name] WHERE name like "Bob%" AND phone_number = '3444444' limit 1,5;

Use a regular expression to find records. Use "REGEXP BINARY" to force case-sensitivity. This finds any record beginning with a.

mysql> SELECT * FROM [table name] WHERE rec RLIKE "^a";

Show unique records

mysql> SELECT DISTINCT [column name] FROM [table name];

Show selected records sorted in an ascending (asc) or descending (desc)

mysql> SELECT [col1],[col2] FROM [table name] ORDER BY [col2] DESC;

Return number of rows

mysql> SELECT COUNT(*) FROM [table name];

Sum column

mysql> SELECT SUM(*) FROM [table name];

To update info already in a table

mysql> UPDATE [table name] SET Select_priv = 'Y',Insert_priv = 'Y',Update_priv = 'Y' where [field name] = 'user';

Delete a row(s) from a table

mysql> DELETE from [table name] where [field name] = 'whatever';

Update database permissions/privilages

mysql> flush privileges;

Delete a column

mysql> alter table [table name] drop column [column name];

Add a new column to db

mysql> alter table [table name] add column [new column name] varchar (20);

Change column name

mysql> alter table [table name] change [old column name] [new column name] varchar (50);

Make a unique column so you get no dupes

mysql> alter table [table name] add unique ([column name]);

Make a column bigger

mysql> alter table [table name] modify [column name] VARCHAR(3);

Delete unique from table

mysql> alter table [table name] drop index [colmn name];

Load a CSV file into a table

mysql> LOAD DATA INFILE '/tmp/filename.csv' replace INTO TABLE [table name] FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n' (field1,field2,field3);

Dump all databases for backup. Backup file is sql commands to recreate all db's

# [mysql dir]/bin/mysqldump -u root -ppassword --opt >/tmp/alldatabases.sql

Dump one database for backup

# [mysql dir]/bin/mysqldump -u username -ppassword --databases databasename >/tmp/databasename.sql

Dump a table from a database

# [mysql dir]/bin/mysqldump -c -u username -ppassword databasename tablename > /tmp/databasename.tablename.sql

Restore database (or database table) from backup

# [mysql dir]/bin/mysql -u username -ppassword databasename < /tmp/databasename.sql

Easy way to do w3c standard complex layout in html

To do complex HTML layout from the scratch is pain and need to have expertise in html and css. It will take lot of time make it w3c standard website.

The best way to do is to choose one good css framework and work on top of it.
I personally suggest "blueprint", http://www.blueprintcss.org/

For example, the following creates simple 3-column layout with header and footer.

<div class="container">
   <div class="span-24">
    The header
   </div>

<div class="span-4">
    The first column
   </div>
   <div class="span-16">
    The center column
   </div>
   <div class="span-4 last">
    The last column
   </div>

<div class="span-24">
    The footer
   </div>
  </div>

Here the div.container is the main div element in this framework 

and everything is wrapped in this element.

div.span-24 means, 24 columns and each spanning 30px with 10px margin 

between each column and the total width comes to 950px, which is a 

good width for 1078 * 768 resolution.

Check the tutorial here: 

https://github.com/joshuaclayton/blueprint-css/wiki/Quick-start-tutorial

Check here the sample layout with blueprint framework: 

http://d2o0t5hpnwv4c1.cloudfront.net/158_blueprint/src/index.html

The best way to handle keyup events for text input element

In general we will use "keyup" event in case if we need to display some results upon search keyword entered by the user. Anytime the user types the keyword, the callback function will be called and displays the result. For example: If user wants to search with "REST", the callback function will be called for 4 times, and the search keywords will be "R", "RE", "RES" and "REST" for each time.

This problem will not be solved even if you add some time out function to delay the call back event. If we add time out when calling the function, then callback function will be executed with the keyword "REST" for 4 times.
To solve this problem, there is a plugin called "TypeWatch" in jQuery which allows the user to enter full keyword, then it executes after some time delay:

Here is the function, which takes 5 parameters as the input.

// callback: The function to call
// wait: The number of milliseconds to wait after the the last key press before firing the callback
// highlight: Highlights the element when it receives focus
// captureLength: Minimum # of characters necessary to fire the callback

$("#search_groups").typeWatch( { 
 wait : 750,
highlight:true, 
callback:renderSearchResult,
captureEnter : true,

minTextLength : 2

});
See demo here: http://dennydotnet.com/typewatch/index.htm
See the plugin: http://plugins.jquery.com/project/TypeWatch

Good article on jQuery

Here is an article which explains how to build large scale applications using jQuery:
http://addyosmani.com/blog/large-scale-jquery/

popups with window.print on body load event doesn't work in chrome

Issue:

Popus with <body onload="window.print();window.close()"> doesn't work in chrome.

solution:

 Use  "setTimeout('print()', 1);" on load event!!
http://groups.google.com/a/chromium.org/group/chromium-bugs/msg/ff8e015c44d28643