Bash on Codrut Constantin Gusoi

Concatenate shell commands

Thu, 13 Oct 2022 08:16:04 +0000

Steps Link to heading

Fetch a command with either:

C-e C-u: go to end of line, cut until beginning of line.
C-a C-k: go to start of line, cut until end of line.

Navigate to older command with:

C-p: previous command.
C-r: search command (use fzf for better results).

Navigate to the end with C-e and type &&.

Now you can paste with C-y.

Prepend to $PATH in bash

Sat, 01 Oct 2022 10:49:32 +0000

You should always check if the value is present in a list before adding it in.

function prepend_path () {
  case ":${PATH}:" in
    *:"$1":*)
    ;;
    *)
      PATH="$1:${PATH}"
  esac
}

Usage Link to heading

prepend_path ~/.local/bin

Cleanup Link to heading

unset prepend_path

Pretty print Linux $PATH

Sun, 25 Sep 2022 10:19:10 +0000

Bash

echo $PATH | sed "s/:/\n/g"

Ruby Version Manager: rbenv

Sun, 18 Sep 2022 10:01:05 +0000

Docker Link to heading

The best way to manage ruby for your project is by using Docker:

If you don’t have a Docker setup yet, you have to suffer, temporarily, by using rbenv. There used to be another tool called rvm for this sort of thing but it’s been abandoned for a long time now, it’s insecure to install from their website, has install errors, and it’s completely broken for newer versions of ruby and newer versions of OpenSSL. Your only real option is to use rbenv.

How to install Homebrew securely

Sat, 17 Sep 2022 12:18:08 +0000

The instructions at https://brew.sh/ are extremely dangerous! Here is how to install homebrew properly.

NOTE: we assume your homebrew path is: ~/Workspace/Hub/brew

Code Link to heading

Clone the repository:

git clone https://github.com/Homebrew/brew.git ~/Workspace/Hub/brew

cd ~/Workspace/Hub/brew

Review the code carefully!
Check the commit sha matches the one from the last commit on the repository website:
```
git rev-parse HEAD
```
Now you have a secure copy of the repository and you can automate the process.

Shell script infinite loop

Fri, 11 Jun 2021 13:24:23 +0000

Useful for all sorts of things:

while true; do echo 'Inside the loop'; sleep 5; done

Bash profiling

Fri, 18 Dec 2020 12:19:25 +0000

Execute these lines in a shell, or put them at the top of your bash script:

set -x
PS4='+ $EPOCHREALTIME ($LINENO) '

Now, every time you execute a command or script, you will see a timestamp, line number, and command/script executed.

export A=1
# + 1608294433.986333 (3) export A=1
# + 1608294433.986378 (3) A=1

export B=2
# + 1608294439.100780 (4) export B=2
# + 1608294439.100807 (4) B=2

[ "$A" == "$B" ] && echo 'Equal' || echo 'Not Equal' && false
# + 1608294491.748071 (5) '[' 1 == 2 ']'
# + 1608294491.748115 (5) echo 'Not Equal'
# Not Equal
# + 1608294491.748200 (5) false

One Liners: Generate random password

Tue, 28 Jul 2020 18:15:13 +0000

Basic command:

tr -dc "a-zA-Z0-9" < /dev/urandom | head -c 32

Print it to STDOUT:

echo $(tr -dc "a-zA-Z0-9" < /dev/urandom | head -c 32)

Save it in an environment variable:

export SECRET_PASSWORD=$(tr -dc "a-zA-Z0-9" < /dev/urandom | head -c 32)

How to Use: shellcheck

Thu, 25 Jun 2020 19:38:41 +0000

Install Link to heading

From package:

# Manjaro / Arch
sudo pacman -S shellcheck

# Alpine
apk add --update shellcheck

From Docker:

docker run --rm -it -v "$PWD":/work -w /work koalaman/shellcheck-alpine:latest sh

Configure Link to heading

Add a .shellcheckrc file containing your rules:

disable=SC2059

Use Link to heading

shellcheck ./path/to/script.sh

How to Use: envsubst

Fri, 12 Jun 2020 22:29:13 +0000

Install Link to heading

# Manjaro / Arch
sudo pacman -S gettext

# Alpine
apk add --update gettext

Usage Link to heading

Create a template input file ./truth.template containing:

Pizza is ${WHAT}

Export your environment variable:

export WHAT=love

Substitute it inside an output file:

envsubst < ./truth.template > ./output.file

You can see the result:

cat ./output.file
# Pizza is love

Real world usage Link to heading

Use it to generate random passwords and save them in env files:

Compile Android projects from CLI

Mon, 08 Jun 2020 17:21:28 +0000

Install java:

sudo pacman -S jdk8-openjdk jre8-openjdk jre8-openjdk-headless

Install Android SDK:

sudo pacman -S snapd
sudo snap install androidsdk

Configure your SDK location in your ~/.bash_profile or ~/.bashrc:

export ANDROID_SDK_ROOT=~/snap/androidsdk/current/AndroidSDK/

Install the platform tools for your target android version:

androidsdk "platform-tools" "platforms;android-28"

Compile the project. This will install all dependencies, make sure to accept licenses when prompted.

./gradlew assembleDebug

If you haven’t done already, then Enable ‘Developer options’ on your phone

How to configure your Bash history

Sat, 25 Apr 2020 18:43:42 +0000

Good Link to heading

export HISTCONTROL=ignoreboth:erasedups
export HISTSIZE=5000000
export HISTFILESIZE=5000000
export HISTFILE=/home/$USER/.bash_history_persistent
shopt -s histappend

export PROMPT_COMMAND="history -a; $PROMPT_COMMAND"

It’s crucial that you change the location of your history file, otherwise it might get accidentally truncated. You always learn this the hard way.

Bad Link to heading

Don’t do:

export PROMPT_COMMAND="history -a; history -c; history -r; $PROMPT_COMMAND"

It will mess up your Ctrl + p and Ctrl + n functionality and that is infinetly more useful than having your command history shared between terminal tabs.

Install Ruby gems in home directory

Sun, 05 Apr 2020 15:26:35 +0000

Create the ~/.gemrc file with the following content:

gem: --no-rdoc --no-ri --user-install

Add these lines to your .bash_profile:

for entry in ~/.gem/ruby/*; do PATH=$entry/bin:$PATH; done
export PATH

export BUNDLE_PATH=~/.gem/bundle

Now you can install gems without needing your root password:

gem install rspec

which rspec
# /home/me/.gem/ruby/2.7.0/bin/rspec

Bundler with a Gemfile:

source 'https://rubygems.org'

gem 'rspec'

You can prefix your commands with bundle exec:

bundle install

bundle exec which rspec
# /home/me/.gem/bundle/ruby/2.7.0/bin/rspec

Don’t forget to clean up your old ruby gems directories:

Install NPM packages in home directory

Sat, 04 Apr 2020 21:41:19 +0000

Create the ~/.npmrc file with the following content:

prefix = "~/.local"

Add the following line to your .bash_profile:

export PATH=~/.local/bin:$PATH

Now you can install a npm package without your root password:

npm install -g eslint

which eslint
# /home/me/.local/bin/eslint

How to Use: fzf

Wed, 01 Apr 2020 19:00:53 +0000

Install Link to heading

sudo pacman -S fzf

Setup Link to heading

Add the following lines to your .bash_profile:

[[ -f /usr/share/fzf/completion.bash   ]] && . /usr/share/fzf/completion.bash
[[ -f /usr/share/fzf/key-bindings.bash ]] && . /usr/share/fzf/key-bindings.bash

Usage Link to heading

You have the following keybindings in an interactive bash shell:

Key binding	Description
`Ctrl + r`	Fuzzy search through your bash history.
`Ctrl + t`	fuzzy search a file in your current directory.

Best used with the following bash config:

Bash on Codrut Constantin Gusoi

Concatenate shell commands

Steps Link to heading

Result Link to heading

Prepend to $PATH in bash

Usage Link to heading

Cleanup Link to heading

Pretty print Linux $PATH

Ruby Version Manager: rbenv

Docker Link to heading

How to install Homebrew securely

Code Link to heading

Shell script infinite loop

Bash profiling

One Liners: Generate random password

How to Use: shellcheck

Install Link to heading

Configure Link to heading

Use Link to heading

How to Use: envsubst

Install Link to heading

Usage Link to heading

Real world usage Link to heading

Compile Android projects from CLI

How to configure your Bash history

Good Link to heading

Bad Link to heading

Install Ruby gems in home directory

Install NPM packages in home directory

How to Use: fzf

Install Link to heading

Setup Link to heading

Usage Link to heading