Tutorials - Page 3 of 5

CSS3 border-radius property can be used to make corners round of a block element. Border radius can have upto 4 values. Here is how a read more

Docker can be used to run nginx in a container. We’ll use Ubuntu Linux (14.04.2) for the purpose of this tutorial. This tutorial assumes that read more

This Chrome extension tutorial will cover building a basic hello world chrome extension where clicking on extension icon will open a popup window containing active read more

CSS pseudo element ::before and ::after (CSS 2 syntax :before and :after) can be used to place some content before or after an element. Most read more

Docker inspect can be used to get information including IP address about a container using its id or name. $ docker inspect [container_name_or_id] To get read more

Some handy command to work with containers. We’ll assume a docker image ubuntu is available on current machine. Run interactive shell (or any other command) read more

To remove a user from a group on Linux, one can use gpasswd or deluser. Here are sample commands. Using gpasswd To remove user1 from read more

It is a good idea to add a user to docker group. In case user is not added to docker group, you may see the read more

Docker is an open-source project that automates the deployment of applications inside software containers. Here is Docker quick start guide on Ubuntu Linux. We’ll use read more

An error in robots.txt can cause Google to stop crawling a section of your site. In such case it is good to update and resubmit read more

Linux (or Unix) command line utilities like awk, sort, uniq, can be used to analyze apache log to get interesting stats. One use case is read more

In case you get lot of emails, its useful to create gmail filters to apply labels automatically and optionally archive matching emails. Gmail search can read more

Chrome extension is very powerful feature of Chrome browser and an extension can be very useful for performing various activities on a web page. This read more

If you want to access pre-release features of Google Chrome, you can download Chrome Canary which is usually few versions ahead of stable Google Chrome. read more

Chrome developer tools can be used to view browser HTTP request and response headers when browser loads a page or makes AJAX calls. Here are read more

PHP function static variable exists only in a local function scope but it does not lose its value after function execution. It can be used read more

If you are building Chrome extensions and want to load extensions from directories, you need to enable Chrome developer mode for extensions. Here are quick read more

When writing bash scripts or running something on command line, last command exit code status is stored in environment variable $?. It can also be read more

On Linux or Unix, error from a command (stderr) can be redirected to stdout or a file. These are the file descriptor id used on read more

PHP has inbuilt function rtrim to remove specific or all trailing whitespaces from end of php string. preg_replace can also be used for this purpose. read more

PHP exec and shell_exec can be used to execute a shell command on server side. exec also populates shell exit return status in one of read more

Linux (or Unix) grep without any options does a regex grep on input stream. To disable regex either one can use grep -F or fgrep. read more

Python map is very useful built-in python function to achieve complex stuff over a list in very short and elegant way. Note that map applies read more

Angularjs basic controller clock example to display date and update it every second. We’ll use controller, template and $timeout. We used AngularJS $timeout here. If read more

Angularjs basic controller example to initialize a number in view, and then increment it on button click. We’ll use controller, template and ng-click directive. The read more

PHP regex whitespace shorthand \s can be used to match whitespace characters. These are the characters it will match. Char Dec val Oct val tab read more

HTML5 shadow dom is part of Web components. It is currently in draft stage and supported by Chrome. It can also be compared with react read more

HTML5 template tag can be used to define template in html and instantiate it when needed. The instantiated template can be inserted in any DOM read more

Javascript DOM method textContent can be used to get the text content inside a DOM. This can be useful to obtain content from a web read more

Javascript DOM method appendChild can be used to append a child to existing DOM element. For example it can be used to append an Image, read more

CORS (cross origin resource sharing) can be used to make AJAX requests to different origins. Here are some points to note: CORS un-aware browser will read more

PHP call_user_func_array() can be used to call a function with arguments in an array. This gives us the flexibility to pass variable number of arguments. read more

PHP func_get_args(), func_get_arg() and func_num_args() can be used to retrieve php function arguments inside a function. This may be useful in debugging. Here are code read more

DOMContentLoaded event is fired when document DOM is ready and before images, etc. are loaded. It is similar to jQuery $(document).ready(). Here is code snippet read more

HTML document ready event is called before image assets, etc. are loaded on the page. window onload handler is called once all assets have been read more

Sometime it is useful to log the calling filename and line number details of the calling file/function in php. One common use case if to read more

Sometime we need to call a function after an image has been loaded. We can attach onload even handler on image either in html itself read more

Attaching a function to windows on load event can be done in multiple ways using plain vanilla Javascript. One option is to use wondow.onload where read more

Javascript querySelector can be used to select and set html of a dom element using css selectors. This can be done with jQuery also. But read more

In Python we frequently need to check if a value is in an array (list) or not. Python x in list can be used for read more

Python has in-built string split function which can be used to split a string on any delimiter and return a python list (array). If no read more

Python built-in data type string is very frequently used in any python program. Here are some examples of using strings to get started with. Print read more

Often we need to delete old file on Linux or Unix which are old (say 30 days or more). Here are some commands which can read more

Gmail can get full very soon with heavy file attachments being very common these days. In case your need to clean your gmail mailbox, easiest read more

Checking if a key exists in an array and possibly has a non empty value are frequently used when writing php code. Accessing value of read more

Checking if a string contains a substring is very frequently occuring use case in PHP code. PHP functions strpos or stripos (case insensitive version) can read more

Sometime we need to block all robots from crawling a web site. This can be needed if you have a stage or sandbox website for read more

Checking if a value exists in array is frequently used in php. PHP in_array() can be used for this check. By default it does not read more

By default Disallow entry in robots.txt is based on url prefix. To block every url beginning with /foo/ the following robots.txt can be used. User-agent: read more

Handy mysql query to get all posts with a missing custom field. We’ll query post_type=page for the purpose of this tutorial. You will have to read more

Splitting a string/text at a delimiter is very common use case in php. One can either use php explode (split on a fixed delimiter) or read more

It may be useful to look at Chrome plugin code at times for debugging purpose. Chrome plugins are stored in the following directory (for user read more

Php regex can use word boundary character (\b) to match a word boundary. Beginning of string if following by a word character will also match read more

Perl command line one liner can be used to replace text in a file using regular expressions (regex). It is very powerful approach for automating read more

Angularjs is a web application framework which has gained lot of popularity in mobile and single page applications. It uses directive ng-app to represent root read more

Css :last-of-type pseudo class apply to an element if it is last sibling among its parent’s direct child elements of same type. Here is an read more

Css :last-child pseudo class apply to an element if it is last sibling in all direct child elements of its parent. It can be used read more

Docker is an open-source project that automates the deployment of applications inside software containers. Here is Docker quick start guide on Mac. Install docker toolbox read more

Css :first-of-type pseudo class apply to an element if it is first sibling among its parent’s direct child elements of same type. Here is an read more

Css :first-child pseudo class apply to an element if it is first sibling in all direct child elements of its parent. Here are some examples. read more

Css :nth-child and :nth-of-type pseudo classes look very similar initially. But these are slightly different. Few points to explain the difference: :nth-child considers all sibling read more

Python filter is very handy python built-in function to filter iterables (e.g. lists) in python. But it returns a list which may consume huge memory read more

Jenkins supports setting build triggers using Jenkins crons. This way build will run at regular interval and possibly Jenkins can send email on failure. Here read more

It is a good idea to frequently take schema dump of all your databases. This may be useful in case there is some accidental change. read more

Python filter is very useful built-in python function to achieve complex stuff over a list in very short and elegant way. Note that filter applies read more

In case can you are using Jenkins shell commands to run tests and are running multiple commands, by default Jenkins exits the comment one shell read more

Checking browser errors (including Javascript errors) is an important use case in testing a website. Javascript errors are hard to QA and can cause bad read more

Sometimes it is useful to iterate over function arguments programmatically. Function arguments can be access using arguments variable. Here is code snippet for this. Note read more

Getting email of a build failure is a common use case in Jenkins. We would want to get notified whenever any build fails and when read more

Regex OR (alternation) in php can be matched using pipe (|) match character. This is very frequently used in regular expressions. Following are some ways read more

It is useful to find out javascript errors in a page automatically. This can help in site quality test automation. Here is selenium code snippet read more

Sometimes we need to perform some action if a file is newer than other file. This can be used to recreate generated file if source read more

Apache lets you log a specific apache sub process environment variable in access log. PHP lets you set apache sub process env variable using apache_setenv. read more

Handy command on Linux/Mac to find all files matching a pattern containing a specific text. This will also print file name. $ find . -type read more

Sometimes we need to create a replica of a project or project with similar configuration in Jenkins. This helps in avoiding entering project configuration data read more

Sometimes we need to use back reference in PHP preg_replace to put back the matched pattern. One example can be if you want to append read more

If you are concatenating multiple css files into once css file, it is useful to have sourcemap in your combined css file in development environment. read more

Gulp is a toolkit to automate tasks primarily in web development workflow. It can automate things like css/js minification, concatenation, etc. Here is quick tutorial read more

LXC (Linux Containers) is an operating-system-level virtualization environment for running multiple isolated Linux systems (containers) on a single Linux control host. Here is a quick read more

To get total DOM elements including children use the following code (this includes root html element also) $(‘*’).length To get all DOM elements in body read more

WordPress will display all posts on a tag archive page which are tagged with that tag. Sometimes we want to exclude posts of more specific read more

It is a good idea to disable spell check in textarea element if it is not meant for pure english text. To disable spell check read more

It is often required to toggle the case of current character in Vim. Vim has lot of other powerful commands related to changing case of read more

PHP set_error_handler can catch various type of php errors in a specific portion of the code. To restore the previous error hander one can call read more

Here are some awk examples to sum an integer column from a file or stdin (standard input) stream. Data used in these examples Awk sum read more

Awk is pretty powerful command line utility to filter lines from a stream. Here are some awk if condition examples. Data used in these examples: read more

To list all DNS records of a domain name use the following dig command (after replacing microsoft.com with desired domain) $ dig microsoft.com any ;; read more

To see the diff of last committed change follow these steps: Find last revision id $ svn update $ svn log -l 1 r4546 | read more

Using svn command line option Use the following diff command to avoid diff context $ svn diff –diff-cmd=diff -x -U0 Option -x passes option -U0 read more

To add a number to a variable in bash, there are many approaches. Some of these are: Declare variable as integer Once a variable is read more

To find and move to matching bracket (curly, square or round) use the following command inside vim once you are in one of the brackets. read more

It is important to maintain healthy xml sitemap for your site. In case you are using Yoast SEO plugin to generate xml sitemap for a read more

The following code can be used to have separate value of posts per page for various archive pages (category, tag, date, author, etc.)

PHP requires regex patterns to have valid delimiters around it. Some languages may not require delimiters (e.g. python). To make code more readable, sometimes we read more

Command to edit a committed revision Example command for revision r4448 $ svn propedit svn:log –revprop -r r4448 hook setup for allowing editing log message read more

In case you need to create a custom link for category or tag, the you can term_link filter. This can be useful in case you read more

Sometime we need to see svn log of all files in a directory (including all files in all its subdirectories). Here are some approaches. Using read more

Convert using array_flip() This works if we need index as value. Using foreach iterator In case we need to set associative array value using array read more

Sometimes we need to populate static variables in php (e.g. populating associative arrays from existing arrays). Easiest way is to define a static function (e.g. read more

Bash associative arrays are supported in bash version 4. Here is a quick start tutorial for using bash associative arrays. Declare and initialize associative array read more

Mysql query – Find term_taxonomy_id from category name Use the following query to find term_taxonomy_id for a category name after replacing “Tutorial” with the category read more

Mysql query – Find term_taxonomy_id for a tag name Use the following query to find term_taxonomy_id for a tag name after replacing “PHP” with the read more

Find term_taxonomy_id for a category name Use the following query to find term_taxonomy_id for a category name after replacing “Tutorials” with the category you want read more

Remove php extension from a specific url To remove php extension from a url (e.g. /foo/bar.php) the following Apache rewrite rule can be used: RewriteRule read more

Cloning table with indexes/triggers and data First create new table with same structure. We’ll use wordpress table wp_posts for the purpose of this tutorial. mysql> read more

get wpdb class method names using get_class_methods Here is the outcome from above code:

PHP – get class name of an object get_class with object as arguments returns its class name. PHP – get filename from class name Here read more

Few notes on Javascript array forEach Array arr is passed to function as local variable a Array arr is also available in function here as read more

Code snippet to check if a given javascript variable is defined. This also covers a variable having null value and non existing entry in an read more

Use rsync dryrun (-n) with -i (or –itemize-changes) to list changed files. $ rsync -n -i -a ./dir1 ./destdir/ cd+++++++ dir1/ >f+++++++ dir1/file1.php >f+++++++ dir1/file2.php read more

for in loop over javascript associative array for in loop over javascript DOM object

Get dictionary key with default if not found using method get() This is better approach in most cases. Get dictionary key using square brackets ([]) read more

Total queries on mysql prompt: mysql> SHOW STATUS like “Queries”; +—————+——–+ | Variable_name | Value | +—————+——–+ | Queries | 278583 | +—————+——–+ 1 row read more

Get post_type page with missing meta_key Get post_type post with missing meta_key

Php regex can use caret (^) for matching from beginning of string and dollar ($) for end of line. Here are some examples using preg_replace. read more

Regex to remove non printable characters from a string Space is first printable char and tilde (~) is last printable ascii char. We replace any read more

Take last 3 characters when string is big enough Take last 3 characters when string is smaller than 3 chars

PHP array – foreach loop on values PHP array – foreach loop on index,values PHP array – foreach loop for modification PHP associative array – read more

Curl with rate limit (both download and upload bandwidth) to 1 KBps (1 kilobytes per second) $ curl –limit-rate 1K https://infoheap.com/ > out.html // or read more

Javascript querySelector() and querySelectorAll() can be used to get DOM element based on given CSS selector. These works on document and element objects both. querySelector() read more

Bash functions can have local variables. This can protect the accidental modification of global variables when function is called inline within same shell. Here are read more

Look ahead and look behind can be very useful to match a pattern which is followed, not followed, preceded or preceded by a certain pattern. read more

svn log can be used to show the log messages for a set of revision(s) and/or path(s). Here are some ways to do svn log read more

Here are some examples you can print strings or variables in python on stdout. Print a string with newline in the end By default python read more

Frequently used python for loop examples. For loop to iterate over a list Iterate on each element of a list Iterate on each index, element read more

Php preg_match (preg_replace) can have greedy (default) or lazy regular expressions. Lazy match is done as soon as a valid match is found. Greedy match read more

Bash built in double square brackets can be used for regex match in if condition. This can be pretty powerful and can be used in read more

Bash scripts can trap EXIT signal and run clean up commands before exit. This is useful if a user kills a script or the script read more

To display a div in browser window center we can use css position value fixed. The left and top value of fixed position are relative read more

Jenkins is an open source continuous integration (CI) tool written in java. It can be used to run (on-demand or periodic) build and test jobs read more

Gmail can be used to send email as different address. It can be handy if you want to use your primary account to receive and read more

Sometimes we need to display a message and then fade it out. jQuery fadeOut will make an element fadeOut (by animating css property opacity) will read more

Get main program directory location In case you have a program main.sh in /opt/tmp which includes utils.sh from /opt/tmp/dir1, then this code will return /opt/tmp read more

Javascript errors can be caught using window.onerror event handler. Whenever a javascript error occurs browser calls this function. In this tutorial we’ll write error handler read more

Npm (Node package manager) is used to install/uninstall and manage node packages. Here are some common commands when using npm on command line on Linux read more

Use apt-get to install imagemagick $ sudo apt-get install imagemagick List binaries in imagemagick $ dpkg -L imagemagick | grep bin /usr/bin /usr/bin/conjure.im6 /usr/bin/composite.im6 /usr/bin/import.im6 read more

Selenium code in python can execute custom Javascript and also return values from webdriver (PhantomJS, Firefox, Chrome. etc.) context. Here is sample code which counts read more

Using functions in bash is fairly useful to organise and reuse code. Here is quick beginner tutorial with examples on using bash functions. Declaring functions read more

Update node source $ curl -sL https://deb.nodesource.com/setup_5.x | sudo -E bash – Check which nodejs will be installed $ apt-cache policy nodejs nodejs: Installed: (none) read more

Use brew to get information on latest imagemagick version $ brew info imagemagick imagemagick: stable 6.9.2-8 (bottled), HEAD Tools and libraries to manipulate images in read more

Find available packages on Mac using brew $ brew search [package name] $ brew search lua lua lua51 luabind luajit homebrew/emacs/lua-mode homebrew/nginx/lua-nginx-module homebrew/versions/lua53 Get info read more

Mac screenshots are saved on Desktop by default. It can cause Desktop to get cluttered very fast. Here are the steps to change default screenshot read more

Here is quick tutorial to use python selenium with PhantomJS as driver. We will fetch a page and assert that page title has certain keyword. read more

Mac supports full screen, window and a specific selection for taking screenshots. You can either store screenshot in a file on Desktop or in clipboard. read more

PHP echo allow comma (,) for concatenating various values in addition to dot (.). This works only for echo though. It is sometimes discussed comma read more

To check if a variable is set or empty, we can use couple of approaches. One approach is to use empty string check (if [ read more

These are few ways of iterating on bash arrays to read and or modify array’s elements in bash on Linux or Mac. Here are some read more

Global variables can be accessed in bash function without declaring anything and when these are modified the behaviour depend on whether function is called in read more

Amazon EC2 api tools have fairly handy utilities to get information and perform various AWS tasks on your instance. Here are quick steps to install read more

There are multiple ways to check if a variable is empty and then set it to some default value. Shell parameter expansion gives us an read more

You can use user and password based authentication to push git changes to GitHub. But it is cumbersome to type user and password with every read more

Command line utility ssh-keygen can be used to generate rsa or dsa public and private keys. By default it generates rsa keys. Here are commands read more

In case you have lost your ssh public key, you can re-generate it from the private key you have. Here is the command to generate read more

We frequently need to center text and images when we are writing HTML/CSS. This can be done by using vertical-align:middle property on the child element read more

We frequently use drag and drop on Mac for copying, creating alias/shortcut or moving files from one folder to another. Mac shows very good mouse read more

Bash variables without double quotes can give surprising results. The special characters inside a variable when not double quoted, gets interpreted by bash. Few points read more

To have newline (\n) and other escape characters in bash strings, we can use $’string’ syntax (ANSI-C Quoting). $’string’ expands to string, with backslash-escaped characters read more

Variable in string approach Use curly braces {} around variable (${VARNAME}) in case text begins with alphanumeric character. Concatenate variable with string Use =+ operator read more

Using Amazon route53 has a huge advantage that it offers a TTL of as low as 60 seconds. This means changing IP for your domain read more

If you are running Windows 10 inside VirtualBox, you may want to enable copy/paster from windows and vice versa. This tutorial should work on any read more

DOM window object has many javascript event handlers attached to it. It may be handy to dump and view all of these. Here is code read more

Curl by default shows progress bar. To hide it -s option can be used. We can also add -S to show errors when -s option read more

To stop a bash script at first error use set -e. To undo it use set +e.

Linux command line tools to send mails are very handy for sending mails from bash scripts. As an example you can send daily php error read more

If you want view the version of currently installed wordpress for a site, here are few approaches. View version using dashboard glance section If you read more

At times we need to force hover state when we are debugging CSS in style inspector in Chrome developers tools. Chrome supports forcing a certain read more

Files or strings in DOS format may have \r (carriage return) along with \n (newline). This may appear as ^M in some editors. Here is read more

We often need to display a table with alternate rows having different colors. We can do it either using CSS3 nth-child selector or using jQuery. read more

PHP supports Heredoc and Newdoc syntax. It is a convenient way to assign multiple lines string to a variable. This makes code more readable. Here read more

Windows 10 can be run in Mac using Virtualbox and Windows 10 OS trial image available from Microsoft’s site. Here are the steps to install read more

At times for large array values we want to log them in one line for better readability. Logging an array in one line is also read more

PHP isset() and empty() are frequently used to check the values of variables. In some cases is_null is also used. Here is a table covering read more

It is sometimes useful to change color of table cells based on values for better presentation and readability. Here is quick code snippet to do read more

Often we want to open Finder window when we are working on Terminal. Here are few scenarios to open Finder window from command line terminal read more

Imagemagick is very powerful tool to process images on command line. If you have multiple images, you can use imagemagick convert utility on Mac or read more

Sometimes we need to check if a filename contains special character etc. One possible approach is to check for alphanumeric characters and few more characters read more

At times we need to take timed screenshots on Mac. Here are two approaches we can use to take timed screenshot on Mac. Screenshot using read more

Ubuntu dpkg-query can be used to find package name given a file name, its full path or partial name. Note that it does not follow read more

System files are hidden on Mac and they don’t show up in Finder search results by default. In case you end up searching stuff which read more

When writing a wrapper bash script, we often need to pass all arguments passed to the wrapper scrip to another script. Here is quick bash read more

WordPress has support for displaying tag cloud using wp_tag_cloud. It displays tag cloud and has support for including and excluding tags and specifying mininum and read more

Mac spotlight and finder are great way to find files on Mac. But Mac also has command line utility mdfind (utility to query meta data) read more

Windows does not have telnet program enabled by default. Telnet is a handy tool to check if a port is up or not at any read more

Sometime we need to run a program as administrator to be able to perform root privileged tasks. e.g. Editing the windows hosts file is only read more

Here is simple python code snippet to see the file location of a python package on command line: $ python -c “import urllib2; print urllib2.__file__;” read more

In case you have multiple gmail accounts you can forward email from one account to another. You can also choose to keep the forwarded email read more

PhantomJS can be used to test websites and for automating various tasks. When testing a website in production, it may not be a good idea read more

Handy mysql query to get all custom keys and values for a post in wordpress. SELECT wp_postmeta.* FROM wp_postmeta JOIN wp_posts ON wp_posts.ID = wp_postmeta.post_id read more

Curl is fairly handy command line utility to fetch a web page. It can also be used to automate various tasks in bash shell scripts. read more

Imagemagick convert is pretty handy tool to manipulate images and can be used to crop an image. This can be useful in automation and also read more

Any user created on Linux may or may not have a password. Linux stores passwords in encrypted format in /etc/shadow. Here is quick command line read more

Giving sudo to a user is frequently occurring activity on Linux. Here are some scenarios and best practices for providing sudo to users on Linux. read more

In WordPress you may want to do certain things only when admin user is viewing a post. Here is quick code snippet to know if read more

Often we need to print a javascript object to console log or somewhere else for debugging purpose. These are some handy ways to dump javascript read more

Phantomjs lets you add hooks when it fetches a web page. Here is code snippet which can be used to print all resources phantomjs fetches read more

Bash code to check if file begins with a string Note the presence of double square brackets ([[ ]]) Bash code to check if file read more

Sometime we need to get file size for the purpose of automation in bash shell script. Here are few ways to get a size of read more

Bash code snippet to check if file exists FILE=/etc/passwd if [ -f $FILE ] ; then echo “$FILE exists and is regular file” else echo read more

Imagemagick convert can be used to compress and screenshot images by changing unique colors, image depth etc. Here are some ways to compress images created read more

Print image unique colors and bit depth $ identify -format “UniqueColors: %k, BitDepth:%q\n” img1.png UniqueColors: 1694, BitDepth:16 Note that when can compress an image with read more