Anoduck’s Das Wiki

Contents:

The comforts of shell

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The comforts of shell

Here is a nice introduction to shell. It explains what they are, what differentiates them from the command line, and the different varieties of shell available.

Terminal Colors

Bash

Here is where I write a nice introduction about the Bourne again shell.

Here is my page to the wiki page for bash –> bash

ZSH

Here is where I take a stab at explaining what ZSH is, and why zsh differs from bash.

Here is my page on zsh –> zsh

Neat tricks

This section is to cover neat tricks that are too cool to be tucked away in a section of their own.

Using EOF to write a file in your shell

cat <<EOF> $FILE
> #!/usr/bin/env bash
> echo "Do something really cool!"
> EOF

Require SuperUser Privileges

While performing some server configuration work, this convenient script was written to make copying the configuration file over and restarting the server more convenient. It’s importance is the simple conditional that requires a user to have SuperUser Privileges in order to run. Appropriate slang included for variety.

#!/usr/bin/env bash

HTTPDIR="/etc/httpd.conf.d"
REPODIR="/local/location/of/files"

if [ "$EUID" -ne 0 ]; then
  echo "Yo! You gotta be root to run this shit! Fool!"
  echo "Try using sudo."
  exit
else
  echo "Nice, Playa! Word to your momma."
  sleep 1
fi

UFILE="$REPODIR/$1"
SFILE="$HTTPDIR/$1"

if ! [[ -f "$UFILE" ]]; then
  echo "Argument must be a configuration file located in $REPODIR"
  exit
fi

USUM=$(cat "$UFILE" | md5)
SSUM=$(cat "$SFILE" | md5)

if [[ "$USUM" == "$SSUM" ]]; then
  echo "Both files are the same."
  exit
else
  if [[ "$UFILE" -nt "$SFILE" ]]; then
    echo "Replacing httpd configuration file and reloading server"
    cp "$UFILE" "$SFILE"
    rcctl restart httpd
    echo "Done."
  else
    if [[ "$SFILE" -nt "$UFILE" ]]; then
      echo "Replacing file in repository."
      cp "$SFILE" "$UFILE"
      chown "$USER" "$UFILE"
      chmod 0755 "$UFILE"
      echo "Done"
    fi
  fi
fi

Restart on configuration file change

This script is worth taking notice, because parts of it have been used numerous times in other scripts to aid in launching applications, and ensuring those applications remain running. This particular script just comes with an additional feature, which is to continuously check configuration files for changes.

#!/usr/bin/env bash

# Variables
CONFIG="$HOME/.config/hypr/waybar"
WAYCONFIG="$CONFIG/config"
WAYSTYLE="$CONFIG/style.css"

# start waybar if not started
if ! pgrep -x "waybar" > /dev/null; then
	hyprctl keyword exec waybar -b "bar" --config "$WAYCONFIG"
fi

# current checksums
current_checksum_config=$(md5sum "$WAYCONFIG")
current_checksum_style=$(md5sum "$WAYSTYLE")

# loop forever
while true; do
	# new checksums
	new_checksum_config=$(md5sum "$WAYCONFIG")
	new_checksum_style=$(md5sum "$WAYSTYLE")

	# if checksums are different
	if [ "$current_checksum_config" != "$new_checksum_config" ] || [ "$current_checksum_style" != "$new_checksum_style" ]; then
		# kill waybar
		killall waybar

		# start waybar
		waybar &

		# update checksums
		current_checksum_config=$new_checksum_config
		current_checksum_style=$new_checksum_style
	fi
done

Common case switch for bash

Just a basic example of using case in bash.

case "$1" in
  start | up)
    vagrant up
    ;;

  *)
    echo "Usage: $0 {start|stop|ssh}"
    ;;
esac

More Advanced Example of a case switch for bash

This example was directly taken from a deprecated script once used to launch a remote desktop session using one of several methods.

while [[ "$1" =~ ^- && ! "$1" == "--" ]]; do case "$1" in
	-a | --autossh )
		run_autossh
		;;
	-s | --ssh )
		RUN_HYPR=false
		run_ssh
		;;
	-r | --hypr )
		RUN_HYPR=true
		run_ssh
		;;
	-k | --kill )
		kill_all
		;;
	-v | --vnc )
		"$VNC_CMD"
		;;
	_)
		run_ssh
		;;
esac; shift; done
if [[ "$1" == '--' ]]; then shift; fi

Download latest Github Release of a project

This is a snippet of a script that will download the latest release of an application.

#!/usr/bin/env bash

PROFILE=""
PROJECT=""
OUTFILE=""
ENDFILE=""
 
VERSION=$(curl -s "https://api.github.com/repos/$PROFILE/$PROJECT/releases/latest" | \grep -Po '"tag_name": *"v\K[^"]*')
 
curl -Lo "$OUTFILE" "https://github.com/$PROFILE/$PROJECT/releases/download/v${VERSION}/$PROJECT_${VERSION}_Linux_x86_64.tar.gz"
 
tar xf $OUTFILE $ENDFILE
 
sudo install $ENDFILE -D -t /usr/local/bin/

Upgrade godns

This takes part of the snippet above and actually integrates it into a working example of upgrading godns. It first checks to see if the current version and the current release are the same, if so nothing is done, if not so it downloads and installs the newest release.

Recursively find and replace string

Quite easily actually.

find /some/path \(-type d -name .git -prune \) -o -type f -print0 | xargs -0 sed -i 's/some_phrase/some_replacement/g'

New Commands

Recently a few new commands have been encountered, that have never been seen before. Unsure if they are new arrivals or if they are older commands which were unknown of. Either way, they listed below.

newgrp

Newgroup allows a user to initiate and finalize changes to group membership without having to log out and in again. This feature becomes handy when the user does not need to lose any established environment variables.

Pushd

Pushd comes from perl, and appears to be part of the standard perl package. The best way to describe the functionality of pushd is to think of it as a temporary change directory command. As it allows the user to designate a directory to change into, and when ready, executing the command again without any arguements then will return the user back to the directory he started out in.