Bash – how to run custom commands at script exit
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
How to display a div in browser window center
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
Install and setup Jenkins on Ubuntu Linux
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
Json online validator
Online Json validator (json syntax/lint checker) Sample valid json strings Simple json string “hello” Simple json array [“hello1”, “hello2”] Simple json associative array { “key1″:”hello1”, read more
Gmail – how to send email from different address
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
How to display auto fade out message using jQuery
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
Bash – how to get main program and current file dir location
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 – catch errors using window.onerror
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
NodeJS – npm beginner tutorial
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
How to install Imagemagick on Ubuntu Linux
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
Python selenium – execute javascript code
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
Bash – how to use functions – quick tutorial
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
How to install node.js on Ubuntu Linux
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
How to install Imagemagick on Mac
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
Mac brew – how to find latest available package without installing
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 – how to change default location for screenshots
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
Python pytest – using selenium with PhantomJS
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
View your browser and device screen width/height – online
Browser window width and height Live data based on your current browser. Resizing browser window will change values here. Property Value outer width,height – x read more
Mac – how to take screenshots
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 – comma (,) vs dot (.) performance benchmarks
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
Bash – how to check if a variable is set
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
Bash – iterate over array
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
Can global variables be modified in bash function?
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
Install Amazon EC2 api tools on Ubuntu Linux
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
Bash – set default value if a variable is empty
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
How to setup password less git push for github
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
How to create ssh public/private keys on command line
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
Generate ssh public key from private key on command line
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
CSS – how to align image and text in center vertically
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
Mac – how to copy, alias, move using drag/drop and mouse pointer indicators for these
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
PHP rawurlencode online
This form can be used to encode a url or string using php rawurlencode function. Additional notes PHP rawurlencode will encode space to %20 The read more
PHP urlencode online
This form can be used to encode a url or string using php urlencode function. Additional notes PHP urlencode will encode space to + The read more
Bash – variables in double quotes vs without quotes
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
Bash – newline and other escape character in string
To have newline (\n) and other escape characters in bash strings, we can use $’string’ syntax (ANSI-C Quoting). $’string’ expands to string, with backslash-escaped characters read more
Bash – append text to a variable
Variable in string approach Use curly braces {} around variable (${VARNAME}) in case text begins with alphanumeric character. Concatenate variable with string Use =+ operator read more
Why and how to use Amazon route53 as DNS
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
Mac VirtualBox – enable copy paster from/to Windows 10
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
Javascript – dump all handlers on window object
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 – how to hide progress bar
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
Bash – how to stop at error
To stop a bash script at first error use set -e. To undo it use set +e.
Linux – sending mail from command using mailutils
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
How to view wordpress current version
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
How to debug :hover in Chrome
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
PHP – convert dos newline to unix format
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
HTML table with alternate color rows
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 – assign multi lines string to a variable
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
How to run windows 10 on Mac using VirtualBox
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
PHP – print array in one line
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 – empty() vs isset() vs is_null() vs boolean check
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
Jquery – change table cells color based on value
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
Mac – open Finder from terminal – quick tip
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 – how to create animation on command line
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
PHP check if a filename is valid
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
Mac – how to take timed screenshot
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 – find file to package
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
Mac Finder – how to search system hidden files
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
Bash – pass all arguments from one script to another
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 – how to create custom tag cloud
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 – search files on command line using mdfind
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
How to enable telnet program on Windows 10
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
How to run a program as administrator on windows 10
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
How to find python package’s file location
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
How to auto forward gmail from one account to another
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 – how to skip Google analytics code when fetching a web page
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
WordPress mysql query to get all custom keys and values for a post
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 – follow redirects
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
How to crop an image using imagemagick convert
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
How to check if a user has password on Linux
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
Linux – providing sudo access to a users – some best practices
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
WordPress how to check if a post is being viewed by admin
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
How to print javascript object to log
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 – how to check what resources are being requested by a page
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 check if file begins with a string
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
Get file size in bytes on Linux
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 shell – check if file or directory exists
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
How to compress screenshot images using imagemagick convert
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
Find image unique colors and bit depth using imagemagick identify
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
WordPress – how to make a post sticky on home page
In wordpress you can make any post sticky and make it appear on home page at top even when there is more recent posts. Here read more
How to show wordpress pages on front page with skip_home custom field
By default WordPress pages donot show up on home page. Only posts are displayed on home page. Here is wordpress php code which can be read more
Fetch wordpress rss feed as FeedBurner user agent on command line
In case you have setup your wordpress feed to redirect to Feedburner url for regular user-agents, you can use either curl or wget (Mac or read more
Get image width and ppi using imagemagick identify on command line
Imagemagick identify is pretty handy utility to get information about an image. You need to have imagemagick installed on your Mac or Linux for the read more
Vim (vi) – multiline search replace with confirmation
Vi (or Vim) is a very powerful and light weight editor which is available on any Linux or Mac. Even if you are working on read more
Mac brew – how to relink installed binaries for a package
When brew installs a package, it also links the binary commands to brew prefix location. In case you have installed a package and for reason read more
How to resize image (including animated gif) using Image magick convert
Imagemagick convert can be used to resize and image (including animated gif). Here are some scenarios where convert can be used to change size of read more
How to edit animated gif speed (FPS) using imagemagick convert
Imagemagick convert can be used to edit animated gif speed (FPS). Here are some scenarios where convert can be used. For these commands to work read more
How to create animated gif using Mac preview
Mac preview can be used to create simple animated gif by taking multiple screenshots of a window and then stitching then together in Mac preview read more
Git – how to view diff for a given commit id
Diff commit id with its first parent commit id Here are some approaches to view diff between first parent of commit id and commit id. read more
Php equal (==) vs identical (===)
Equal (==) compares two values after type changing one value to another. Identical compare values and types both and returns true only if they both read more
Mysql find current timezone offset
Print current local and global timezone SELECT @@global.time_zone, @@session.time_zone; Here is the outcome @@global.time_zone @@session.time_zone +05:30 +05:30 Find timezone offset using convert_tz select TIMEDIFF(now(), convert_tz(now(), read more
Mysql difference between CURDATE() and NOW()
Mysql CURDATE CURDATE() returns only date portion of date in current timezone. select CURDATE(); Outcome 2015-12-02 Mysql NOW NOW() returns full time in current timezone. read more
Query to find recently modified posts in WordPress
It can be sometime handy to query recently modified (last month or last few days) posts in wordpress mysql tables. Here are some handy queries: read more
Vim – how to go back to last edited line/context
Sometimes we are editing a certain section of code in vi and then navigate to different section for reference. It is tedious to come back read more
Running php eval on code with tags
php eval on code wrapped in php tags Here is the code snippet which calls php eval on a code which is wrapped in <?php read more
WordPress – how to add filter to description meta tag
If you using Yoast seo plugin, then you can use its filter wpseo_metadesc to change meta description tag as per your needs. Typically you want read more
WordPress – write custom php log to separate file
Why write php log to separate file Using default php error log in wordpress php code for informational messages can pollute php error log file. read more
Mysql query to find all yoast meta description
In case you are are using Yoast plugin for SEO and using it to enter meta post description, you can query meta descriptions of all read more
jQuery – difference between html() and text()
Jquery can be used to set content on and element (div, etc.) using text() and html() methods. Methods text(content) will first convert the content using read more
How to open vim at previous location
Vi (or Vim) editor can remember location at the time of exiting a file. This can be fairly convenient while editing files during development. .vimrc read more
Using WordPress custom field for displaying code
WordPress custom fields (post meta keys) can be used to store key value pairs for a post. This can be very useful to store code read more