What is this?

A collection of shell scripts written just for fun and learning aimed towards UNIX and Linux systems.

Possible questions

• Why is the commit history overwritten so much?

To start from scratch and correct any mistakes I made (e.g illogical commit dates).

• Why do I get an error message when running git pull?

Because I forcefully pushed commits. To fix it, delete the repository's directory and clone it again.

Dependencies ✅

• bash >= 5
• git >= 2.40.1
• coreutils >= 9.1
• Any POSIX compliant shell (e.g dash)

Per script

dl	si	che	chk4up	screenshot
youtube-dl >= 2021.12.17	apt >= 2.7.0	shadow >= 4.12.3	pamac >= 10	scrot >= 1.9
	dnf >= 4.15.0		libnotify >= 0.8.2	libnotify >= 0.8.2
	pacman >= 6
	ncurses >= 6.4

Installation ⬇

0. Get required software.
1. Clone repository.

git clone https://github.com/tricantivu/bashy.git.

2. Run (from repository's root):

./install.sh

Coding style

Sections

1. Indentation
2. Shebang
3. Quoting
4. Variables
5. Constants
6. Functions
7. Arithmetic
8. Loops
9. Conditions
10. Switch-Case
11. Traps
12. ShellCheck

Indentation

• 4 spaces.

for (( ;; )); do

    printf 'y\n'

done

Shebang

Use the env command without options that are not specified by POSIX (e.g -S).

---

POSIX scripts:

#!/usr/bin/env sh

---

Non-POSIX scripts:

#!/usr/bin/env bash

---

Quoting

• Single quote strings without parameter expansions.

printf '%s\n' 'Success!'

echo 'Failure!'

• Do not quote parameters expanding to numerical values.

Variables

• Names are snake cased. Except for loop counters, they must be lowercase letters.

i=0 j=0 k=0

parent_node

• Initialized or declared without declare builtin command.

Constants

• Names must be in SCREAMING_SNAKE_CASE.

readonly INT_MAX=32767

• Initialized with readonly builtin command.

readonly LONG_MAX=2147483647

Functions

• Define them with inline curly braces.

• Write a space after the closing parenthesis.

• Names are snake cased, abbreviated or full words.

getaddrinfo() {

    :
}

get_current_dir_name() {

    :
}

Arithmetic

• Avoid floating point numbers.

• Surround expressions with a space.

(( i * 3 ))

• Check parameters expand to one or more without operators.

(( UID )) || exit 1

• Check parameters expand to zero without operators.

(( EUID )) && exit 1

• If you are not scripting with a POSIX shell, use unary operators to increment or decrement variables. Otherwise, use arithmetic expansions.

---

Non-POSIX:

(( i++ ))

(( j-- ))

---

POSIX:

i=$(( i + 1 ))

j=$(( j - 1 ))

---

Loops

• Bodies must preceded and followed by a blank line.

for i in {1..10}; do

    echo "${i}"

done

while (( RANDOM < 1000 )); do

    echo 'Hello'

done

until (( 1 = 2 )); do

    :

done

• Do not write them inline.

• Preferably, iterate using brace expansions. However, C like loops are allowed.

Conditions

• Use logical operators for trivial conditions.

if [[ "${REPLY}" == [Nn] ]]; then
    exit

fi

⤵

[[ "${REPLY}" == [Nn] ]] && exit

Equivalently for negated conditions:

if ! [[ -f /etc/fstab ]]; then
    echo 'Your system is broken!'

fi

⤵

[[ -f /etc/fstab ]] || echo 'Your system is broken!'

• Use command groups when there is more than one statement to execute if a command fails or succeeds (i.e $? > 0 and $? == 0 respectively).

while read -r line; do

    [[ "${line}" =~ ^root ]] && break

done < /etc/passwd || {

    echo 'Hmm?'

    exit 1
}

while read -r line; do

    [[ "${line}" =~ ^(/usr)?/bin/bash$ ]] && break

done < /etc/shells && {

    echo 'Bash is a valid login shell'

    exit 0
}

"Switch-case"

• Patterns must be followed by a blank line.

• Semicolons must be on a new line and at the same indentation level as its corresponding pattern.

case "${USER}" in
    (root)

        echo 'I am almost Groot!'
    ;;
    (groot)

        echo 'I am Groot!'
    ;;
esac

Traps

• Use complete signal names.

• Sort command lines by length.

trap 'rm "${TMPFILE}"' EXIT
trap "printf '\e[2J\e[H'" EXIT

ShellCheck

• Do not prefix codes with SC.

# shellcheck disable=2086
echo $*

Scripts

rss - Add feeds to Newsboat.

chk4up - Update AUR packages with desktop notifications.

si - System information script.

screenshot - scrot wrapper.

spi - Process information command line utility.

che - Change account expiration dates with relative time units.

sysexits - Lookup sysexits code names, values and descriptions.