November 25, 2019 in Learning, Tips and Tricks

what is the use of microk8s

What is Kubernetes

Kubernetes clusters host containerised applications in a reliable and scalable way. Having DevOps in mind, Kubernetes makes maintenance tasks such as upgrades dead simple.

What is MicroK8s

MicroK8s is a CNCF certified upstream Kubernetes deployment that runs entirely on your workstation or edge device. Being a snap it runs all Kubernetes services natively (i.e. no virtual machines) while packing the entire set of libraries and binaries needed. Installation is limited by how fast you can download a couple of hundred megabytes and the removal of MicroK8s leaves nothing behind.

In this tutorial you’ll learn how to…

• Get your Kubernetes cluster up and running
• Enable core Kubernetes addons such as dns and dashboard
• Control your cluster from the kubectl CLI client
• Deploy your first container workload

You will only need …

• A machine with Linux

Integrated commands

There are many commands that ship with MicroK8s. We’ve only seen the essential ones in this tutorial. Explore the others at your own convenience:

• microk8s.status: Provides an overview of the MicroK8s state (running / not running) as well as the set of enabled addons
• microk8s.enable: Enables an addon
• microk8s.disable: Disables an addon
• microk8s.kubectl: Interact with kubernetes
• microk8s.config: Shows the kubernetes config file
• microk8s.istioctl: Interact with the istio services; needs the istio addon to be enabled
• microk8s.inspect: Performs a quick inspection of the MicroK8s intallation
• microk8s.reset: Resets the infrastructure to a clean state
• microk8s.stop: Stops all kubernetes services
• microk8s.start: Starts MicroK8s after it is being stopped

Lightweight Kubernetes done right

The smallest, fastest, fully-conformant Kubernetes that tracks upstream releases and makes clustering trivial. MicroK8s is great for offline development, prototyping, and testing. Use it on a VM as a small, cheap, reliable k8s for CI/CD. The best kubernetes for appliances. Develop IoT apps for k8s and deploy them to MicroK8s on your Linux boxes.

Reliable, fast, small, upstream.

• Fast install : Get a full Kubernetes system running in under 60 seconds.
• Secure : Runs safely on your laptop with state of the art isolation.
• Upstream : CNCF binaries delivered to your laptop, with updates and upgrades.
• Complete : Includes a docker registry so you can make containers, push them, and deploy them all on your laptop.
• Featureful : Cool things you probably want to try on a small, standard K8s are all built-in. Just enable them and go.
• Updates : Get the daily build if you want it, or betas and milestones, or just stable point releases.
• Upgrades : When a new major version comes out, upgrade with a single command (or automatically).
• GPGPU Passthrough : Give MicroK8s a GPGPU and your docker containers can get all nice and CUDA.
• Small : Use MicroK8s in your CI/CD pipelines and get on with your day without headaches.

November 25, 2019 in Learning, Tips and Tricks

What is DevOps?

DevOps is a set of practices that automates the processes between software development and IT teams, in order that they can build, test, and release software faster and more reliably. The concept of DevOps is founded on building a culture of collaboration between teams that historically functioned in relative siloes. The promised benefits include increased trust, faster software releases, ability to solve critical issues quickly, and better manage unplanned work.

At its essence, DevOps is a culture, a movement, a philosophy.

It’s a firm handshake between development and operations that emphasizes a shift in mindset, better collaboration, and tighter integration. It unites agile, continuous delivery, automation, and much more, to help development and operations teams be more efficient, innovate faster, and deliver higher value to businesses and customers.

History of DevOps

The DevOps movement started to coalesce some time between 2007 and 2008, when IT operations and software development communities got vocal about what they felt was a fatal level of dysfunction in the industry.

They railed against the traditional software development model, which called for those who write the code to be organizationally and functionally apart from those who deploy and support that code.

Developers and IT/Ops professionals had separate (and often competing) objectives, separate department leadership, separate key performance indicators by which they were judged, and often worked on separate floors or even separate buildings. The result was siloed teams concerned only with their own fiefdoms, long hours, botched releases, and unhappy customers.

Surely there’s a better way, they said. So the two communities got together and started talking – with people like Patrick Dubois, Gene Kim, and John Willis driving the conversation.

What began in online forums and local meet-ups is now a major theme in the software zeitgeist, which is probably what brought you here! You and your team are feeling the pain caused by siloed teams and broken lines of communication within your company.

You’re using agile methodologies for planning and development, but still struggling to get that code out the door without a bunch of drama. You’ve heard a few things about DevOps and the seemingly magical effect it can have on teams and think “I want some of that magic.”

The bad news is that DevOps isn’t magic, and transformations don’t happen overnight. The good news is that you don’t have to wait for upper management to roll out a large-scale initiative. By understanding the value of DevOps and making small, incremental changes, your team can embark on the DevOps journey right away. Let’s look at each of these benefits in detail.

What’s in it for you?

Collaboration and trust

Culture is the #1 success factor in DevOps. Building a culture of shared responsibility, transparency and faster feedback is the foundation of every high performing DevOps team.

Teams that work in siloes often don’t adhere to the ‘systems thinking’ of DevOps. ‘Systems thinking’ is being aware of how your actions not only affect your team, but all the other teams involved in the release process. Lack of visibility and shared goals means lack of dependency planning, misaligned priorities, finger pointing, and ‘not our problem’ mentality, resulting in slower velocity and substandard quality. DevOps is that change in mindset of looking at the development process holistically and breaking down the barrier between Dev and Ops.

Release faster and work smarter

Speed is everything. Teams that practice DevOps release more frequently, with higher quality and stability.

Lack of automated test and review cycles block the release to production and poor incident response time kills velocity and team confidence. Disparate tools and processes increase OPEX, lead to context switching, and slow down momentum. Through automation and standardized tools and processes, teams can increase productivity and release more frequently with fewer hiccups.

Accelerate time to resolution

The team with the fastest feedback loop is the team that thrives. Full transparency and seamless communication enable DevOps teams to minimize downtime and resolve issues faster than ever before.

If critical issues aren’t resolved quickly, customer satisfaction tanks. Key issues slip through the cracks in the absence of open communication, resulting in increased tension and frustration among teams. Open communication helps Dev and Ops teams swarm on issues, fix incidents, and unblock the release pipeline faster.

Better manage unplanned work

Unplanned work is a reality that every team faces–a reality that most often impacts team productivity. With established processes and clear prioritization, the Dev and Ops teams can better manage unplanned work while continuing to focus on planned work.

Transitioning and prioritizing unplanned work across different teams and systems is inefficient and distracts from work at hand. However, through raised visibility and proactive retrospection, teams can better anticipate and share unplanned work.

November 24, 2019 in Learning, Tips and Tricks

What are the disadvantages of AngularJS?

Advantages of AngularJS:

1. Open source JavaScript framework, developed by Google
2. MVC architecture
3. Write less do more
4. Modify DOM directly
5. Two way data binding
6. Quiet a number of ways to do same thins

Disadvantages of AngularJS:

1. Limitation in watchers (not more than 2000)
2. Not built for mobile devices
3. Multiple ways to do the same thing, it is very hard for a developer to tell which is the best way.
4. Two way binding checks all the variables twice for updating which makes the UI slow

If you are new to AngularJS, I would recommend to learn Angular 2 or above.

Angular 2 is a completely rewritten of Angular 1.X so you can learn it without knowing about AngularJS or Angular 1.x.

Following are the Advantages of AngularJS

• allows us to create a single page application
• follows MVC pattern
• predefined form validations
• supports animation
• open source
• cross-browser compliant
• supports two-way data binding
• its code is unit testable

Following are the Disadvantages of AngularJS

• JavaScript Dependent: If end user disables JavaScript, AngularJS will not work.
• Not Secured: It is JavaScript based framework so it is not safe to authenticate user through AngularJS only.

With AngularJS, you don’t have the ability to compose many NG-apps on the same page. This can cause name clashes.

Advantages Of AngularJS

Here are some of the compelling advantages of AngularJS:

Built by Google

AngularJS has been developed as well as maintained by dedicated Google engineers. This means that there is a huge community out there for you to learn from. Apart from that, there are engineers that can help you tackle any challenges you face on the way. It also means that clients get what they want.

Great MVC

As mentioned earlier, most frameworks require programmers to splitting the app into multiple MVC components. After that, the programmer has to write a code to put them together again. AngularJS, however, strings it together automatically. That saves you time, and reduces the app’s time-to-market.

Intuitive

AngularJS is more intuitive as it makes use of HTML as a declarative language. Moreover, it is less brittle for reorganizing.

Comprehensive

AngularJS is a comprehensive solution for rapid front-end development. It does not need any other plugins or frameworks. Moreover, there are a range of other features that include Restful actions, data building, dependency injection, enterprise-level testing, etc.

Unit Testing Ready

AngularJS is unit testing ready, and that is one of its most compelling advantages.

Apart from these, there are a range of other advantages that make AngularJS as popular as it is.

Disadvantages Of AngularJS

Along with advantages, you will always come across disadvantages of any platform. That’s the case with AngularJS too.

Here’s a compilation of some of the drawbacks of using AngularJS:

Confusion

There are multiple ways to do the same thing with AngularJS. Sometimes, it can be hard for novices to say which way is better for a task. Hence, it is imperative for programmers to develop an understanding of the various components and how they help.

Lagging UI

If there are more than 2000 watchers, it can get the UI to severely lag. This means that the possible complexity of Angular Forms is limited. This includes big data grids and lists.

November 24, 2019 in Learning, Tips and Tricks

Syncs directories and S3 prefixes. Recursively copies new and updated files from the source directory to the destination. Only creates folders in the destination if they contain one or more files.

Examples

The following sync command syncs objects under a specified prefix and bucket to files in a local directory by uploading the local files to s3. A local file will require uploading if the size of the local file is different than the size of the s3 object, the last modified time of the local file is newer than the last modified time of the s3 object, or the local file does not exist under the specified bucket and prefix. In this example, the user syncs the bucket mybucket to the local current directory. The local current directory contains the files test.txt and test2.txt. The bucket mybucket contains no objects:

aws s3 sync . s3://mybucket

Output:

upload: test.txt to s3://mybucket/test.txt
upload: test2.txt to s3://mybucket/test2.txt

The following sync command syncs objects under a specified prefix and bucket to objects under another specified prefix and bucket by copying s3 objects. A s3 object will require copying if the sizes of the two s3 objects differ, the last modified time of the source is newer than the last modified time of the destination, or the s3 object does not exist under the specified bucket and prefix destination. In this example, the user syncs the bucket mybucket to the bucket mybucket2. The bucket mybucket contains the objects test.txt and test2.txt. The bucket mybucket2 contains no objects:

aws s3 sync s3://mybucket s3://mybucket2

Output:

copy: s3://mybucket/test.txt to s3://mybucket2/test.txt
copy: s3://mybucket/test2.txt to s3://mybucket2/test2.txt

The following sync command syncs files in a local directory to objects under a specified prefix and bucket by downloading s3 objects. A s3 object will require downloading if the size of the s3 object differs from the size of the local file, the last modified time of the s3 object is newer than the last modified time of the local file, or the s3 object does not exist in the local directory. Take note that when objects are downloaded from s3, the last modified time of the local file is changed to the last modified time of the s3 object. In this example, the user syncs the current local directory to the bucket mybucket. The bucket mybucket contains the objects test.txt and test2.txt. The current local directory has no files:

aws s3 sync s3://mybucket .

Output:

download: s3://mybucket/test.txt to test.txt
download: s3://mybucket/test2.txt to test2.txt

The following sync command syncs objects under a specified prefix and bucket to files in a local directory by uploading the local files to s3. Because the –delete parameter flag is thrown, any files existing under the specified prefix and bucket but not existing in the local directory will be deleted. In this example, the user syncs the bucket mybucket to the local current directory. The local current directory contains the files test.txt and test2.txt. The bucket mybucket contains the object test3.txt:

aws s3 sync . s3://mybucket --delete

Output:

upload: test.txt to s3://mybucket/test.txt
upload: test2.txt to s3://mybucket/test2.txt
delete: s3://mybucket/test3.txt

The following sync command syncs objects under a specified prefix and bucket to files in a local directory by uploading the local files to s3. Because the –exclude parameter flag is thrown, all files matching the pattern existing both in s3 and locally will be excluded from the sync. In this example, the user syncs the bucket mybucket to the local current directory. The local current directory contains the files test.jpg and test2.txt. The bucket mybucket contains the object test.jpg of a different size than the local test.jpg:

aws s3 sync . s3://mybucket --exclude "*.jpg"

Output:

upload: test2.txt to s3://mybucket/test2.txt

The following sync command syncs files under a local directory to objects under a specified prefix and bucket by downloading s3 objects. This example uses the –exclude parameter flag to exclude a specified directory and s3 prefix from the sync command. In this example, the user syncs the local current directory to the bucket mybucket. The local current directory contains the files test.txt and another/test2.txt. The bucket mybucket contains the objects another/test5.txt and test1.txt:

aws s3 sync s3://mybucket/ . --exclude "*another/*"

Output:

download: s3://mybucket/test1.txt to test1.txt

The following sync command syncs files between two buckets in different regions:

aws s3 sync s3://my-us-west-2-bucket s3://my-us-east-1-bucket --source-region us-west-2 --region us-east-1

November 18, 2019 in Learning, Tips and Tricks

SUMMARY OF LESS COMMANDS

Less command is linux utility which can be used to read contents of text file one page(one screen) per time. It has faster access because if file is large, it don’t access complete file, but access it page by page.

For example, if it’s a large file and you are reading it using any text editor, then the complete file will be loaded to main memory, but less command don’t load entire file, but load it part by part, which makes it faster.

      Commands marked with * may be preceded by a number, N.
      Notes in parentheses indicate the behavior if N is given.
      A key preceded by a caret indicates the Ctrl key; thus ^K is ctrl-K.

  h  H                 Display this help.
  q  :q  Q  :Q  ZZ     Exit.
 ---------------------------------------------------------------------------

                           MOVING

  e  ^E  j  ^N  CR  *  Forward  one line   (or N lines).
  y  ^Y  k  ^K  ^P  *  Backward one line   (or N lines).
  f  ^F  ^V  SPACE  *  Forward  one window (or N lines).
  b  ^B  ESC-v      *  Backward one window (or N lines).
  z                 *  Forward  one window (and set window to N).
  w                 *  Backward one window (and set window to N).
  ESC-SPACE         *  Forward  one window, but don't stop at end-of-file.
  d  ^D             *  Forward  one half-window (and set half-window to N).
  u  ^U             *  Backward one half-window (and set half-window to N).
  ESC-)  RightArrow *  Right one half screen width (or N positions).
  ESC-(  LeftArrow  *  Left  one half screen width (or N positions).
  ESC-}  ^RightArrow   Right to last column displayed.
  ESC-{  ^LeftArrow    Left  to first column.
  F                    Forward forever; like "tail -f".
  ESC-F                Like F but stop when search pattern is found.
  r  ^R  ^L            Repaint screen.
  R                    Repaint screen, discarding buffered input.
        ---------------------------------------------------
        Default "window" is the screen height.
        Default "half-window" is half of the screen height.
 ---------------------------------------------------------------------------

                          SEARCHING

  /pattern          *  Search forward for (N-th) matching line.
  ?pattern          *  Search backward for (N-th) matching line.
  n                 *  Repeat previous search (for N-th occurrence).
  N                 *  Repeat previous search in reverse direction.
  ESC-n             *  Repeat previous search, spanning files.
  ESC-N             *  Repeat previous search, reverse dir. & spanning files.
ESC-u                Undo (toggle) search highlighting.
  &pattern          *  Display only matching lines
        ---------------------------------------------------
        A search pattern may be preceded by one or more of:
        ^N or !  Search for NON-matching lines.
        ^E or *  Search multiple files (pass thru END OF FILE).
        ^F or @  Start search at FIRST file (for /) or last file (for ?).
        ^K       Highlight matches, but don't move (KEEP position).
        ^R       Don't use REGULAR EXPRESSIONS.
 ---------------------------------------------------------------------------

                           JUMPING

  g  <  ESC-<       *  Go to first line in file (or line N).
  G  >  ESC->       *  Go to last line in file (or line N).
  p  %              *  Go to beginning of file (or N percent into file).
  t                 *  Go to the (N-th) next tag.
  T                 *  Go to the (N-th) previous tag.
  {  (  [           *  Find close bracket } ) ].
  }  )  ]           *  Find open bracket { ( [.
  ESC-^F <c1> <c2>  *  Find close bracket <c2>.
  ESC-^B <c1> <c2>  *  Find open bracket <c1>
        ---------------------------------------------------
        Each "find close bracket" command goes forward to the close bracket
          matching the (N-th) open bracket in the top line.
        Each "find open bracket" command goes backward to the open bracket
          matching the (N-th) close bracket in the bottom line.

  m<letter>            Mark the current position with <letter>.
  '<letter>            Go to a previously marked position.
  ''                   Go to the previous position.
  ^X^X                 Same as '.
        ---------------------------------------------------
        A mark is any upper-case or lower-case letter.
        Certain marks are predefined:
             ^  means  beginning of the file
             $  means  end of the file
 ---------------------------------------------------------------------------

                        CHANGING FILES

  :e [file]            Examine a new file.
  ^X^V                 Same as :e.
  :n                *  Examine the (N-th) next file from the command line.
  :p                *  Examine the (N-th) previous file from the command line.
  :x                *  Examine the first (or N-th) file from the command line.
  :d                   Delete the current file from the command line list.
  =  ^G  :f            Print current file name.
 ---------------------------------------------------------------------------

                    MISCELLANEOUS COMMANDS

  -<flag>              Toggle a command line option [see OPTIONS below].
  --<name>             Toggle a command line option, by name.
  _<flag>              Display the setting of a command line option.
  __<name>             Display the setting of an option, by name.
  +cmd                 Execute the less cmd each time a new file is examined.

  !command             Execute the shell command with $SHELL.
  |Xcommand            Pipe file between current pos & mark X to shell command.
  s file               Save input to a file.
  v                    Edit the current file with $VISUAL or $EDITOR.
  V                    Print version number of "less".
 ---------------------------------------------------------------------------

                           OPTIONS

        Most options may be changed either on the command line,
        or from within less by using the - or -- command.
        Options may be given in one of two forms: either a single
        character preceded by a -, or a name preceded by --.

  -?  ........  --help
                  Display help (from command line).
  -a  ........  --search-skip-screen
                  Search skips current screen.
  -A  ........  --SEARCH-SKIP-SCREEN
                  Search starts just after target line.
  -b [N]  ....  --buffers=[N]
                  Number of buffers.
  -B  ........  --auto-buffers
                  Don't automatically allocate buffers for pipes.
  -c  ........  --clear-screen
                  Repaint by clearing rather than scrolling.
  -d  ........  --dumb
                  Dumb terminal.
 -D [xn.n]  .  --color=xn.n
                  Set screen colors. (MS-DOS only)
  -e  -E  ....  --quit-at-eof  --QUIT-AT-EOF
                  Quit at end of file.
  -f  ........  --force
                  Force open non-regular files.
  -F  ........  --quit-if-one-screen
                  Quit if entire file fits on first screen.
  -g  ........  --hilite-search
                  Highlight only last match for searches.
  -G  ........  --HILITE-SEARCH
                  Don't highlight any matches for searches.
  -h [N]  ....  --max-back-scroll=[N]
                  Backward scroll limit.
  -i  ........  --ignore-case
                  Ignore case in searches that do not contain uppercase.
  -I  ........  --IGNORE-CASE
                  Ignore case in all searches.
  -j [N]  ....  --jump-target=[N]
                  Screen position of target lines.
  -J  ........  --status-column
                  Display a status column at left edge of screen.
  -k [file]  .  --lesskey-file=[file]
                  Use a lesskey file.
  -K            --quit-on-intr
                  Exit less in response to ctrl-C.
  -L  ........  --no-lessopen
                  Ignore the LESSOPEN environment variable.
  -m  -M  ....  --long-prompt  --LONG-PROMPT
                  Set prompt style.
  -n  -N  ....  --line-numbers  --LINE-NUMBERS
                  Don't use line numbers.
  -o [file]  .  --log-file=[file]
                  Copy to log file (standard input only).
  -O [file]  .  --LOG-FILE=[file]
                  Copy to log file (unconditionally overwrite).
  -p [pattern]  --pattern=[pattern]
                  Start at pattern (from command line).
  -P [prompt]   --prompt=[prompt]
                  Define new prompt.
  -q  -Q  ....  --quiet  --QUIET  --silent --SILENT
                  Quiet the terminal bell.
  -r  -R  ....  --raw-control-chars  --RAW-CONTROL-CHARS
  Output "raw" control characters.
  -s  ........  --squeeze-blank-lines
                  Squeeze multiple blank lines.
  -S  ........  --chop-long-lines
                  Chop (truncate) long lines rather than wrapping.
  -t [tag]  ..  --tag=[tag]
                  Find a tag.
  -T [tagsfile] --tag-file=[tagsfile]
                  Use an alternate tags file.
  -u  -U  ....  --underline-special  --UNDERLINE-SPECIAL
                  Change handling of backspaces.
  -V  ........  --version
                  Display the version number of "less".
  -w  ........  --hilite-unread
                  Highlight first new line after forward-screen.
  -W  ........  --HILITE-UNREAD
                  Highlight first new line after any forward movement.
  -x [N[,...]]  --tabs=[N[,...]]
                  Set tab stops.
  -X  ........  --no-init
                  Don't use termcap init/deinit strings.
  -y [N]  ....  --max-forw-scroll=[N]
                  Forward scroll limit.
  -z [N]  ....  --window=[N]
                  Set size of window.
  -" [c[c]]  .  --quotes=[c[c]]
                  Set shell quote characters.
  -~  ........  --tilde
                  Don't display tildes after end of file.
  -# [N]  ....  --shift=[N]
                  Horizontal scroll amount (0 = one half screen width)
      ........  --no-keypad
                  Don't send termcap keypad init/deinit strings.
      ........  --follow-name
                  The F command changes files if the input file is renamed.
      ........  --use-backslash
                  Subsequent options use backslash as escape char.


 ---------------------------------------------------------------------------

                          LINE EDITING

 These keys can be used to edit text being entered
        on the "command line" at the bottom of the screen.

 RightArrow ..................... ESC-l ... Move cursor right one character.
 LeftArrow ...................... ESC-h ... Move cursor left one character.
 ctrl-RightArrow  ESC-RightArrow  ESC-w ... Move cursor right one word.
 ctrl-LeftArrow   ESC-LeftArrow   ESC-b ... Move cursor left one word.
 HOME ........................... ESC-0 ... Move cursor to start of line.
 END ............................ ESC-$ ... Move cursor to end of line.
 BACKSPACE ................................ Delete char to left of cursor.
 DELETE ......................... ESC-x ... Delete char under cursor.
 ctrl-BACKSPACE   ESC-BACKSPACE ........... Delete word to left of cursor.
 ctrl-DELETE .... ESC-DELETE .... ESC-X ... Delete word under cursor.
 ctrl-U ......... ESC (MS-DOS only) ....... Delete entire line.
 UpArrow ........................ ESC-k ... Retrieve previous command line.
 DownArrow ...................... ESC-j ... Retrieve next command line.
 TAB ...................................... Complete filename & cycle.
 SHIFT-TAB ...................... ESC-TAB   Complete filename & reverse cycle.
 ctrl-L ................................... Complete filename, list all.

November 18, 2019 in Learning, Tips and Tricks

Unix Less Command: Tips for Effective Navigation

The navigation keys in less command are similar to Vim editor. In this article, let us look at few less command navigation and other operations which will make you a better command line warrior.

1. Less Command – Search Navigation

Once you’ve opened a log file (or any file) using less file-name, use the following keys to search. Please note that the match will be highlighted automatically by default.

Forward Search

• / – search for a pattern which will take you to the next occurrence.
• n – for next match in forward
• N – for previous match in backward

Backward Search

• ? – search for a pattern which will take you to the previous occurrence.
• n – for next match in backward direction
• N – for previous match in forward direction

Tip: If you dont bother about which direction the search is happening, and you want to search file path, or URL, such as “/home/ramesh/”, you can use backward search (?pattern) which will be handy as you don’t want to escape slashes each time.

Search Path
In forward: /\/home\/aditya\/
In backward: ?/home/aditya/

2. Less Command – Screen Navigation

Use the following screen navigation commands while viewing large log files.

• CTRL+F – forward one window
• CTRL+B – backward one window
• CTRL+D – forward half window
• CTRL+U – backward half window

3. Less Command – Line navigation

In a smaller chunk of data, where you want to locate particular error, you may want to navigate line by line using these keys:

• j – navigate forward by one line
• k – navigate backward by one line

4. Less Command – Other Navigations

The following are other navigation operations that you can use inside the less pager.

• G – go to the end of file
• g – go to the start of file
• q or ZZ – exit the less pager

5. Simulate tail -f inside less pager – Press F

Once you’ve opened a file using less command, any content that is appended to the file after that will not be displayed automatically. However, you can press F less command will show the status ‘waiting for data‘. This is as similar to ‘tail -f’.

6. Less Command – Count magic

Similar to Vim editor navigation command, you can give 10j to scroll 10 lines down, or 10k to go up by 10 lines.

• 10j – 10 lines forward.
• 10k – 10 lines backward.
• CTRL+G – show the current file name along with line, byte and percentage statistics.

7. Other useful Less Command Operations

• v – using the configured editor edit the current file.
• h – summary of less commands
• &pattern – display only the matching lines, not all.

8. Open any types of files using less command

less command can be used to open and view the following 10 different file types:

1. PDF File – *.pdf
2. Word Document- *.doc
3. Image Files – *.gif, *.jpg, *.jpeg, *.png
4. TAR Files – *.tar
5. TAR Files with gzip – *.tar.gz
6. Zip Files – *.zip
7. Gzip and Gzip2 Files – *.gz and *.bz2
8. ISO Files
9. Debian Files – *.deb
10. RPM Files – *.rpm

Set the LESSOPEN environment variable to lesspipe

First, make sure the following is set in the environment variable.

$ set | grep less
LESSOPEN='|/usr/bin/lesspipe.sh %s'

Please note that you can also do the following to setup the lesspipe.

$ eval "($lesspipe)"

$ cat ~/.bashrc
eval "($lesspipe)"

• lesspipe, lessfile are the input preprocessor for less, which lets it to open all types of files.
• lesspipe allows you to open while the process of conversion is going on using pipe.
• lessfile completes the conversion first, and then displays the content. This writes the converted thing to a temporary file then displays it.
• You can also write your own input preprocessor, and use it.

File Type 1: How to open a pdf file?

It shows all the text in the pdf file clearly, but ignores the images. The output may have some special characters here and there. But it is definitely readable.

File Type 1: How to open a pdf file?

It shows all the text in the pdf file clearly, but ignores the images. The output may have some special characters here and there. But it is definitely readable.

$ less Linux-101-Hacks.pdf
^LLinux 101 Hacks
www.thegeekstuff.com
o
o
o
Chapter 1: Powerful CD Command Hacks
cd is one of the most frequently used commands during a UNIX session.
The cd command hacks mentioned in this chapter will boost your productivity

File Type 2: How to open a word document file?

$ less pdb.doc
The Python Debugger Pdb
=======================

To use the debugger in its simplest form:

        >>> import pdb
        >>> pdb.run

The debugger's prompt is Pdb.  This will stop in the first
function call in

File Type 3: How to open a jpg, jpeg, png file?

While opening a image file (jpeg, jpg and png), less command shows the following information:

• Name of the file
• Type of file
• Number of pixels — width & height
• Size of the file

$ less testfile.jpeg
testfile.jpeg JPEG 2304x1728 2304x1728+0+0 DirectClass 8-bit 1.57222mb 0.550u 0:02

Note: Similar kind of information will be displayed for other image file types.

9. Less Command – Marked navigation

When you are viewing a large log file using less command, you can mark a particular position and return back to that place again by using that mark.

• ma – mark the current position with the letter ‘a’,
• ‘a – go to the marked position ‘a’.

10. Less Command – Multiple file paging

Method 1: You can open multiple files by passing the file names as arguments.

$ less file1 file2

Method 2: While you are viewing file1, use :e to open the file2 as shown below.

$ less file1
:e file2

Navigation across files: When you opened more than two files ( for e.g – less * ), use the following keys to navigate between files.

• :n – go to the next file.
• :p – go to the previous file.