It's a note not a blog

How to Escape Character when Running SSH Remote Command

Tags: linux, ssh April 8, 2020 4:18 AM

Solution of Escaping Character on SSH

The solution is DO NOT escape it. Use cat HEREDOC to build the string of commands and then pass it to SSH.

$ export VARIABLE="FOO BAR"
$ cat <<EOF | ssh user@myserver bash
echo "This is complex command"
echo "Another command that take a $VARIABLE."
sudo mkdir /tmp/foo && echo "SUCCESS"
EOF

If you have a lot of $ dollar signs in your script and do not want local shell to interpret it then use single quote HEREDOC.

$ export VARIABLE_NAME="FOO BAR"
$ cat <<'EOF' | ssh user@myserver bash
export VARIABLE="SSH VAR"
echo "This is complex command"
echo "Another command that take a $VARIABLE name."
sudo mkdir /tmp/foo && echo "SUCCESS"
EOF

On command above the variable $VARIABLE value is "SSH VAR" since it is took the value from remote server not from local machine.

Variable Variables in Shell

Tags: bash, shell, variable March 10, 2020 8:12 PM

0 comments

Subtitute Variable inside Variable in Bash

Example below is using Bash for variable variables subtitution.

$ hello="Hello World"
$ foobar="hello"
$ echo "${!foobar}"
Hello World

Subtitute Variable inside Variable using eval

This is for other shell which do not recognize "${!}" syntax. It utilise eval so use it with caution.

$ hello="Hello World"
$ foobar="hello"
$ eval echo "\$${foobar}"
Hello World

References for Variable Variables in Shell

Terraform: Force Destroy Resource when prevent_destroy is true

Tags: bash, cloud, perl, terraform March 3, 2020 6:55 AM

1 comments

How to Force Destroy Resource in Terraform

Terraform resource that having lifecycle prevent_destroy = true can not be destroyed. You need to manually edit the file inplace and change the value prevent_destroy to false manually each time you want to destroy the resource. Instead of having to edit manually and make git status dirty we can automate this using simple shell script.

Automate Force Destroy Resource in Terraform

The idea is simple.

Search all *.tf files and look the value of prevent_default = true to prevent_default = false
Run terraform destroy command
Revert the changes back to prevent_default = true

Here is the implementation in Bash.

#!/bin/bash

$ find . -name '*.tf' -type f \
-exec perl -i -pe 's@prevent_destroy = true@prevent_destroy = false@g' {} \;

# Run terraform destroy
[ "$IS_PLAN" = "yes" ] && terraform plan -destroy || terraform destroy $@

# Revert the changes
$ find . -name '*.tf' -type f \
 -exec perl -i -pe 's@prevent_destroy = false@prevent_destroy = true@g' {} \;

Save the file with name e.g: terraform-force-destroy.sh. To issue terraform plan -destroy command use the following.

$ IS_PLAN=yes bash terraform-force-destroy.sh

To force destroy the resource use the following command.

$ bash terraform-force-destroy.sh -auto-approve

You can give normal terraform's arguments just like the original terraform destroy.

References for Terraform Force Destroy

Expose module in global scope using Browserify or Webpack

Tags: browserify, exports, javascript, webpack October 25, 2019 6:05 AM

0 comments

Goal

You want to expose a module as in global scope so it can be called in HTML file. For example we will create a small function for reversing a string. We will expose it as StrReverse.

// File main.js
module.exports = function(str) {
  return str.split('').reverse().join('');
}

Browserify

$ browserify --standalone StrReverse main.js --outfile bundle.js

The key is --standalone parameter.

Webpack

$ webpack-cli --mode=none --output-library StrReverse main.js --output bundle.js

The key is --output-library parameter.

Test in HTML

Create a HTML file and include bundle.js via <script> tag.

<!DOCTYPE html>
<html>
<body>
<script src="bundle.js"></script>
var reversed = StrReverse("Hello World");
document.write(reversed);
</body>
</html>

Compile Swoole Extension on MacOS using Homebrew

Tags: extension, homebrew, macos, php, swoole July 29, 2019 10:59 PM

0 comments

What is Swoole

Swoole is Production-Grade Async programming Framework for PHP. It helps you write high-performance asynchronous non-blocking I/O. Similar with Go or NodeJS.

How to Compile using Homebrew

I am using MacOS High Sierra and PHP 7.2.20.

$ export LD_LIBRARY_PATH=$( brew --prefix openssl )/lib
$ export CPATH=$( brew --prefix openssl)/include
$ export PKG_CONFIG_PATH=$( brew --prefix openssl )/lib/pkgconfig
$ pecl install swoole
...
Configuring for:
PHP Api Version:         20170718
Zend Module Api No:      20170718
Zend Extension Api No:   320170718
enable sockets supports? [no] : yes
enable openssl support? [no] : yes
enable http2 support? [no] : no
enable mysqlnd support? [no] : no
...
... some long message about compiling
...
Build process completed successfully
Installing '/usr/local/Cellar/php@7.2/7.2.20/include/php/ext/swoole/config.h'
Installing '/usr/local/Cellar/php@7.2/7.2.20/pecl/20170718/swoole.so'
install ok: channel://pecl.php.net/swoole-4.4.2
Extension swoole enabled in php.ini

MySQL DISTINCT with Case Sensitive

Tags: distinct, mysql, query March 14, 2019 9:55 AM

0 comments

Goals

We want MySQL distinct to use case sensitive grouping because by default MySQL use case insensitive.

Solution of MySQL DISTINCT case sensitive

We can use binary operator to convert the character set.

SELECT DISTINCT CAST(expr as BINARY)

As an alternative we can just use BINARY.

SELECT BINARY expr

References

Disable Word Wrap on MySQL Shell

Tags: mysql, shell, word-wrap March 8, 2019 8:54 PM

0 comments

Goals

Turn off or disable word wrap on MySQL shell

Solution of Disable Word Wrap on MySQL Shell

We can use external pager such as less to do the job. Pager in MySQL shell actually is a pipe to another program.

mysql> pager less -SFX
PAGER set to 'less -SFX'

That's it. Simple and easy. Now when you have very long output horizontally it will not wrap.

Reference

http://blog.clearandfizzy.com/post/145657760526/mysql-turn-off-word-wrap

It's a note not a blog

How to Escape Character when Running SSH Remote Command

Solution of Escaping Character on SSH

Variable Variables in Shell

Subtitute Variable inside Variable in Bash

Subtitute Variable inside Variable using eval

References for Variable Variables in Shell

Terraform: Force Destroy Resource when prevent_destroy is true

How to Force Destroy Resource in Terraform

Automate Force Destroy Resource in Terraform

References for Terraform Force Destroy

Expose module in global scope using Browserify or Webpack

Goal

Browserify

Webpack

Test in HTML

Compile Swoole Extension on MacOS using Homebrew

What is Swoole

How to Compile using Homebrew

MySQL DISTINCT with Case Sensitive

Goals

Solution of MySQL DISTINCT case sensitive

References

Disable Word Wrap on MySQL Shell

Goals

Solution of Disable Word Wrap on MySQL Shell

Reference

Tags

Archive

Popular Post