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📖 A collection of pure bash alternatives to external processes. I'm adding extra code snippets to the README

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NEW: pure sh bible (📖 A collection of pure POSIX sh alternatives to external processes).


pure bash bible

A collection of pure bash alternatives to external processes.


The goal of this book is to document commonly-known and lesser-known methods of doing various tasks using only built-in bash features. Using the snippets from this bible can help remove unneeded dependencies from scripts and in most cases make them faster. I came across these tips and discovered a few while developing neofetch, pxltrm and other smaller projects.

The snippets below are linted using shellcheck and tests have been written where applicable. Want to contribute? Read the CONTRIBUTING.md. It outlines how the unit tests work and what is required when adding snippets to the bible.

See something incorrectly described, buggy or outright wrong? Open an issue or send a pull request. If the bible is missing something, open an issue and a solution will be found.


This book is also available to purchase on leanpub. https://leanpub.com/bash

Or you can buy me a coffee.


Table of Contents


FOREWORD

A collection of pure bash alternatives to external processes and programs. The bash scripting language is more powerful than people realise and most tasks can be accomplished without depending on external programs.

Calling an external process in bash is expensive and excessive use will cause a noticeable slowdown. Scripts and programs written using built-in methods (where applicable) will be faster, require fewer dependencies and afford a better understanding of the language itself.

The contents of this book provide a reference for solving problems encountered when writing programs and scripts in bash. Examples are in function formats showcasing how to incorporate these solutions into code.

STRINGS

Trim leading and trailing white-space from string

This is an alternative to sed, awk, perl and other tools. The function below works by finding all leading and trailing white-space and removing it from the start and end of the string. The : built-in is used in place of a temporary variable.

Example Function:

trim_string() {
    # Usage: trim_string "   example   string    "
    : "${1#"${1%%[![:space:]]*}"}"
    : "${_%"${_##*[![:space:]]}"}"
    printf '%s\n' "$_"
}

Example Usage:

$ trim_string "    Hello,  World    "
Hello,  World

$ name="   John Black  "
$ trim_string "$name"
John Black

Trim all white-space from string and truncate spaces

This is an alternative to sed, awk, perl and other tools. The function below works by abusing word splitting to create a new string without leading/trailing white-space and with truncated spaces.

Example Function:

# shellcheck disable=SC2086,SC2048
trim_all() {
    # Usage: trim_all "   example   string    "
    set -f
    set -- $*
    printf '%s\n' "$*"
    set +f
}

Example Usage:

$ trim_all "    Hello,    World    "
Hello, World

$ name="   John   Black  is     my    name.    "
$ trim_all "$name"
John Black is my name.

Use regex on a string

The result of bash's regex matching can be used to replace sed for a large number of use-cases.

CAVEAT: This is one of the few platform dependent bash features. bash will use whatever regex engine is installed on the user's system. Stick to POSIX regex features if aiming for compatibility.

CAVEAT: This example only prints the first matching group. When using multiple capture groups some modification is needed.

Example Function:

regex() {
    # Usage: regex "string" "regex"
    [[ $1 =~ $2 ]] && printf '%s\n' "${BASH_REMATCH[1]}"
}

Example Usage:

$ # Trim leading white-space.
$ regex '    hello' '^\s*(.*)'
hello

$ # Validate a hex color.
$ regex "#FFFFFF" '^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$'
#FFFFFF

$ # Validate a hex color (invalid).
$ regex "red" '^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$'
# no output (invalid)

Example Usage in script:

is_hex_color() {
    if [[ $1 =~ ^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$ ]]; then
        printf '%s\n' "${BASH_REMATCH[1]}"
    else
        printf '%s\n' "error: $1 is an invalid color."
        return 1
    fi
}

read -r color
is_hex_color "$color" || color="#FFFFFF"

# Do stuff.

Split a string on a delimiter

CAVEAT: Requires bash 4+

This is an alternative to cut, awk and other tools.

Example Function:

split() {
   # Usage: split "string" "delimiter"
   IFS=$'\n' read -d "" -ra arr <<< "${1//$2/$'\n'}"
   printf '%s\n' "${arr[@]}"
}

Example Usage:

$ split "apples,oranges,pears,grapes" ","
apples
oranges
pears
grapes

$ split "1, 2, 3, 4, 5" ", "
1
2
3
4
5

# Multi char delimiters work too!
$ split "hello---world---my---name---is---john" "---"
hello
world
my
name
is
john

Change a string to lowercase

CAVEAT: Requires bash 4+

Example Function:

lower() {
    # Usage: lower "string"
    printf '%s\n' "${1,,}"
}

Example Usage:

$ lower "HELLO"
hello

$ lower "HeLlO"
hello

$ lower "hello"
hello

Change a string to uppercase

CAVEAT: Requires bash 4+

Example Function:

upper() {
    # Usage: upper "string"
    printf '%s\n' "${1^^}"
}

Example Usage:

$ upper "hello"
HELLO

$ upper "HeLlO"
HELLO

$ upper "HELLO"
HELLO

Reverse a string case

CAVEAT: Requires bash 4+

Example Function:

reverse_case() {
    # Usage: reverse_case "string"
    printf '%s\n' "${1~~}"
}

Example Usage:

$ reverse_case "hello"
HELLO

$ reverse_case "HeLlO"
hElLo

$ reverse_case "HELLO"
hello

Trim quotes from a string

Example Function:

trim_quotes() {
    # Usage: trim_quotes "string"
    : "${1//\'}"
    printf '%s\n' "${_//\"}"
}

Example Usage:

$ var="'Hello', \"World\""
$ trim_quotes "$var"
Hello, World

Strip all instances of pattern from string

Example Function:

strip_all() {
    # Usage: strip_all "string" "pattern"
    printf '%s\n' "${1//$2}"
}

Example Usage:

$ strip_all "The Quick Brown Fox" "[aeiou]"
Th Qck Brwn Fx

$ strip_all "The Quick Brown Fox" "[[:space:]]"
TheQuickBrownFox

$ strip_all "The Quick Brown Fox" "Quick "
The Brown Fox

Strip first occurrence of pattern from string

Example Function:

strip() {
    # Usage: strip "string" "pattern"
    printf '%s\n' "${1/$2}"
}

Example Usage:

$ strip "The Quick Brown Fox" "[aeiou]"
Th Quick Brown Fox

$ strip "The Quick Brown Fox" "[[:space:]]"
TheQuick Brown Fox

Strip pattern from start of string

Example Function:

lstrip() {
    # Usage: lstrip "string" "pattern"
    printf '%s\n' "${1##$2}"
}

Example Usage:

$ lstrip "The Quick Brown Fox" "The "
Quick Brown Fox

Strip pattern from end of string

Example Function:

rstrip() {
    # Usage: rstrip "string" "pattern"
    printf '%s\n' "${1%%$2}"
}

Example Usage:

$ rstrip "The Quick Brown Fox" " Fox"
The Quick Brown

Percent-encode a string

Example Function:

urlencode() {
    # Usage: urlencode "string"
    local LC_ALL=C
    for (( i = 0; i < ${#1}; i++ )); do
        : "${1:i:1}"
        case "$_" in
            [a-zA-Z0-9.~_-])
                printf '%s' "$_"
            ;;

            *)
                printf '%%%02X' "'$_"
            ;;
        esac
    done
    printf '\n'
}

Example Usage:

$ urlencode "https://github.com/dylanaraps/pure-bash-bible"
https%3A%2F%2Fgithub.com%2Fdylanaraps%2Fpure-bash-bible

Decode a percent-encoded string

Example Function:

urldecode() {
    # Usage: urldecode "string"
    : "${1//+/ }"
    printf '%b\n' "${_//%/\\x}"
}

Example Usage:

$ urldecode "https%3A%2F%2Fgithub.com%2Fdylanaraps%2Fpure-bash-bible"
https://github.com/dylanaraps/pure-bash-bible

Check if string contains a sub-string

Using a test:

if [[ $var == *sub_string* ]]; then
    printf '%s\n' "sub_string is in var."
fi

# Inverse (substring not in string).
if [[ $var != *sub_string* ]]; then
    printf '%s\n' "sub_string is not in var."
fi

# This works for arrays too!
if [[ ${arr[*]} == *sub_string* ]]; then
    printf '%s\n' "sub_string is in array."
fi

Using a case statement:

case "$var" in
    *sub_string*)
        # Do stuff
    ;;

    *sub_string2*)
        # Do more stuff
    ;;

    *)
        # Else
    ;;
esac

Check if string starts with sub-string

if [[ $var == sub_string* ]]; then
    printf '%s\n' "var starts with sub_string."
fi

# Inverse (var does not start with sub_string).
if [[ $var != sub_string* ]]; then
    printf '%s\n' "var does not start with sub_string."
fi

Check if string ends with sub-string

if [[ $var == *sub_string ]]; then
    printf '%s\n' "var ends with sub_string."
fi

# Inverse (var does not end with sub_string).
if [[ $var != *sub_string ]]; then
    printf '%s\n' "var does not end with sub_string."
fi

ARRAYS

Reverse an array

Enabling extdebug allows access to the BASH_ARGV array which stores the current function’s arguments in reverse.

CAVEAT: Requires shopt -s compat44 in bash 5.0+.

Example Function:

reverse_array() {
    # Usage: reverse_array "array"
    shopt -s extdebug
    f()(printf '%s\n' "${BASH_ARGV[@]}"); f "$@"
    shopt -u extdebug
}

Example Usage:

$ reverse_array 1 2 3 4 5
5
4
3
2
1

$ arr=(red blue green)
$ reverse_array "${arr[@]}"
green
blue
red

Remove duplicate array elements

Create a temporary associative array. When setting associative array values and a duplicate assignment occurs, bash overwrites the key. This allows us to effectively remove array duplicates.

CAVEAT: Requires bash 4+

CAVEAT: List order may not stay the same.

Example Function:

remove_array_dups() {
    # Usage: remove_array_dups "array"
    declare -A tmp_array

    for i in "$@"; do
        [[ $i ]] && IFS=" " tmp_array["${i:- }"]=1
    done

    printf '%s\n' "${!tmp_array[@]}"
}

Example Usage:

$ remove_array_dups 1 1 2 2 3 3 3 3 3 4 4 4 4 4 5 5 5 5 5 5
1
2
3
4
5

$ arr=(red red green blue blue)
$ remove_array_dups "${arr[@]}"
red
green
blue

Random array element

Example Function:

random_array_element() {
    # Usage: random_array_element "array"
    local arr=("$@")
    printf '%s\n' "${arr[RANDOM % $#]}"
}

Example Usage:

$ array=(red green blue yellow brown)
$ random_array_element "${array[@]}"
yellow

# Multiple arguments can also be passed.
$ random_array_element 1 2 3 4 5 6 7
3

Cycle through an array

Each time the printf is called, the next array element is printed. When the print hits the last array element it starts from the first element again.

arr=(a b c d)

cycle() {
    printf '%s ' "${arr[${i:=0}]}"
    ((i=i>=${#arr[@]}-1?0:++i))
}

Toggle between two values

This works the same as above, this is just a different use case.

arr=(true false)

cycle() {
    printf '%s ' "${arr[${i:=0}]}"
    ((i=i>=${#arr[@]}-1?0:++i))
}

LOOPS

Loop over a range of numbers

Alternative to seq.

# Loop from 0-100 (no variable support).
for i in {0..100}; do
    printf '%s\n' "$i"
done

Loop over a variable range of numbers

Alternative to seq.

# Loop from 0-VAR.
VAR=50
for ((i=0;i<=VAR;i++)); do
    printf '%s\n' "$i"
done

Loop over an array

arr=(apples oranges tomatoes)

# Just elements.
for element in "${arr[@]}"; do
    printf '%s\n' "$element"
done

Loop over an array with an index

arr=(apples oranges tomatoes)

# Elements and index.
for i in "${!arr[@]}"; do
    printf '%s\n' "${arr[i]}"
done

# Alternative method.
for ((i=0;i<${#arr[@]};i++)); do
    printf '%s\n' "${arr[i]}"
done

Loop over the contents of a file

while read -r line; do
    printf '%s\n' "$line"
done < "file"

Loop over files and directories

Don’t use ls.

# Greedy example.
for file in *; do
    printf '%s\n' "$file"
done

# PNG files in dir.
for file in ~/Pictures/*.png; do
    printf '%s\n' "$file"
done

# Iterate over directories.
for dir in ~/Downloads/*/; do
    printf '%s\n' "$dir"
done

# Brace Expansion.
for file in /path/to/parentdir/{file1,file2,subdir/file3}; do
    printf '%s\n' "$file"
done

# Iterate recursively.
shopt -s globstar
for file in ~/Pictures/**/*; do
    printf '%s\n' "$file"
done
shopt -u globstar

FILE HANDLING

CAVEAT: bash does not handle binary data properly in versions < 4.4.

Read a file to a string

Alternative to the cat command.

file_data="$(<"file")"

Read a file to an array (by line)

Alternative to the cat command.

# Bash <4 (discarding empty lines).
IFS=$'\n' read -d "" -ra file_data < "file"

# Bash <4 (preserving empty lines).
while read -r line; do
    file_data+=("$line")
done < "file"

# Bash 4+
mapfile -t file_data < "file"

Get the first N lines of a file

Alternative to the head command.

CAVEAT: Requires bash 4+

Example Function:

head() {
    # Usage: head "n" "file"
    mapfile -tn "$1" line < "$2"
    printf '%s\n' "${line[@]}"
}

Example Usage:

$ head 2 ~/.bashrc
# Prompt
PS1='➜ '

$ head 1 ~/.bashrc
# Prompt

Get the last N lines of a file

Alternative to the tail command.

CAVEAT: Requires bash 4+

Example Function:

tail() {
    # Usage: tail "n" "file"
    mapfile -tn 0 line < "$2"
    printf '%s\n' "${line[@]: -$1}"
}

Example Usage:

$ tail 2 ~/.bashrc
# Enable tmux.
# [[ -z "$TMUX"  ]] && exec tmux

$ tail 1 ~/.bashrc
# [[ -z "$TMUX"  ]] && exec tmux

Get the number of lines in a file

Alternative to wc -l.

Example Function (bash 4):

lines() {
    # Usage: lines "file"
    mapfile -tn 0 lines < "$1"
    printf '%s\n' "${#lines[@]}"
}

Example Function (bash 3):

This method uses less memory than the mapfile method and works in bash 3 but it is slower for bigger files.

lines_loop() {
    # Usage: lines_loop "file"
    count=0
    while IFS= read -r _; do
        ((count++))
    done < "$1"
    printf '%s\n' "$count"
}

Example Usage:

$ lines ~/.bashrc
48

$ lines_loop ~/.bashrc
48

Count files or directories in directory

This works by passing the output of the glob to the function and then counting the number of arguments.

Example Function:

count() {
    # Usage: count /path/to/dir/*
    #        count /path/to/dir/*/
    printf '%s\n' "$#"
}

Example Usage:

# Count all files in dir.
$ count ~/Downloads/*
232

# Count all dirs in dir.
$ count ~/Downloads/*/
45

# Count all jpg files in dir.
$ count ~/Pictures/*.jpg
64

Create an empty file

Alternative to touch.

# Shortest.
>file

# Longer alternatives:
:>file
echo -n >file
printf '' >file

Extract lines between two markers

Example Function:

extract() {
    # Usage: extract file "opening marker" "closing marker"
    while IFS=$'\n' read -r line; do
        [[ $extract && $line != "$3" ]] &&
            printf '%s\n' "$line"

        [[ $line == "$2" ]] && extract=1
        [[ $line == "$3" ]] && extract=
    done < "$1"
}

Example Usage:

# Extract code blocks from MarkDown file.
$ extract ~/projects/pure-bash/README.md '```sh' '```'
# Output here...

FILE PATHS

Get the directory name of a file path

Alternative to the dirname command.

Example Function:

dirname() {
    # Usage: dirname "path"
    local tmp=${1:-.}

    [[ $tmp != *[!/]* ]] && {
        printf '/\n'
        return
    }

    tmp=${tmp%%"${tmp##*[!/]}"}

    [[ $tmp != */* ]] && {
        printf '.\n'
        return
    }

    tmp=${tmp%/*}
    tmp=${tmp%%"${tmp##*[!/]}"}

    printf '%s\n' "${tmp:-/}"
}

Example Usage:

$ dirname ~/Pictures/Wallpapers/1.jpg
/home/black/Pictures/Wallpapers

$ dirname ~/Pictures/Downloads/
/home/black/Pictures

Get the base-name of a file path

Alternative to the basename command.

Example Function:

basename() {
    # Usage: basename "path" ["suffix"]
    local tmp

    tmp=${1%"${1##*[!/]}"}
    tmp=${tmp##*/}
    tmp=${tmp%"${2/"$tmp"}"}

    printf '%s\n' "${tmp:-/}"
}

Example Usage:

$ basename ~/Pictures/Wallpapers/1.jpg
1.jpg

$ basename ~/Pictures/Wallpapers/1.jpg .jpg
1

$ basename ~/Pictures/Downloads/
Downloads

VARIABLES

Assign and access a variable using a variable

$ hello_world="value"

# Create the variable name.
$ var="world"
$ ref="hello_$var"

# Print the value of the variable name stored in 'hello_$var'.
$ printf '%s\n' "${!ref}"
value

Alternatively, on bash 4.3+:

$ hello_world="value"
$ var="world"

# Declare a nameref.
$ declare -n ref=hello_$var

$ printf '%s\n' "$ref"
value

Name a variable based on another variable

$ var="world"
$ declare "hello_$var=value"
$ printf '%s\n' "$hello_world"
value

ESCAPE SEQUENCES

Contrary to popular belief, there is no issue in utilizing raw escape sequences. Using tput abstracts the same ANSI sequences as if printed manually. Worse still, tput is not actually portable. There are a number of tput variants each with different commands and syntaxes (try tput setaf 3 on a FreeBSD system). Raw sequences are fine.

Text Colors

NOTE: Sequences requiring RGB values only work in True-Color Terminal Emulators.

Sequence What does it do? Value
\e[38;5;<NUM>m Set text foreground color. 0-255
\e[48;5;<NUM>m Set text background color. 0-255
\e[38;2;<R>;<G>;<B>m Set text foreground color to RGB color. R, G, B
\e[48;2;<R>;<G>;<B>m Set text background color to RGB color. R, G, B

Text Attributes

NOTE: Prepend 2 to any code below to turn it's effect off (examples: 21=bold text off, 22=faint text off, 23=italic text off).

Sequence What does it do?
\e[m Reset text formatting and colors.
\e[1m Bold text.
\e[2m Faint text.
\e[3m Italic text.
\e[4m Underline text.
\e[5m Blinking text.
\e[7m Highlighted text.
\e[8m Hidden text.
\e[9m Strike-through text.

Cursor Movement

Sequence What does it do? Value
\e[<LINE>;<COLUMN>H Move cursor to absolute position. line, column
\e[H Move cursor to home position (0,0).
\e[<NUM>A Move cursor up N lines. num
\e[<NUM>B Move cursor down N lines. num
\e[<NUM>C Move cursor right N columns. num
\e[<NUM>D Move cursor left N columns. num
\e[s Save cursor position.
\e[u Restore cursor position.

Erasing Text

Sequence What does it do?
\e[K Erase from cursor position to end of line.
\e[1K Erase from cursor position to start of line.
\e[2K Erase the entire current line.
\e[J Erase from the current line to the bottom of the screen.
\e[1J Erase from the current line to the top of the screen.
\e[2J Clear the screen.
\e[2J\e[H Clear the screen and move cursor to 0,0.

PARAMETER EXPANSION

Indirection

Parameter What does it do?
${!VAR} Access a variable based on the value of VAR.
${!VAR*} Expand to IFS separated list of variable names starting with VAR.
${!VAR@} Expand to IFS separated list of variable names starting with VAR. If double-quoted, each variable name expands to a separate word.

Replacement

Parameter What does it do?
${VAR#PATTERN} Remove shortest match of pattern from start of string.
${VAR##PATTERN} Remove longest match of pattern from start of string.
${VAR%PATTERN} Remove shortest match of pattern from end of string.
${VAR%%PATTERN} Remove longest match of pattern from end of string.
${VAR/PATTERN/REPLACE} Replace first match with string.
${VAR//PATTERN/REPLACE} Replace all matches with string.
${VAR/PATTERN} Remove first match.
${VAR//PATTERN} Remove all matches.

Length

Parameter What does it do?
${#VAR} Length of var in characters.
${#ARR[@]} Length of array in elements.

Expansion

Parameter What does it do?
${VAR:OFFSET} Remove first N chars from variable.
${VAR:OFFSET:LENGTH} Get substring from N character to N character.
(${VAR:10:10}: Get sub-string from char 10 to char 20)
${VAR:: OFFSET} Get first N chars from variable.
${VAR:: -OFFSET} Remove last N chars from variable.
${VAR: -OFFSET} Get last N chars from variable.
${VAR:OFFSET:-OFFSET} Cut first N chars and last N chars.

Case Modification

Parameter What does it do? CAVEAT
${VAR^} Uppercase first character. bash 4+
${VAR^^} Uppercase all characters. bash 4+
${VAR,} Lowercase first character. bash 4+
${VAR,,} Lowercase all characters. bash 4+
${VAR~} Reverse case of first character. bash 4+
${VAR~~} Reverse case of all characters. bash 4+

Default Value

Parameter What does it do?
${VAR:-STRING} If VAR is empty or unset, use STRING as its value.
${VAR-STRING} If VAR is unset, use STRING as its value.
${VAR:=STRING} If VAR is empty or unset, set the value of VAR to STRING.
${VAR=STRING} If VAR is unset, set the value of VAR to STRING.
${VAR:+STRING} If VAR is not empty, use STRING as its value.
${VAR+STRING} If VAR is set, use STRING as its value.
${VAR:?STRING} Display an error if empty or unset.
${VAR?STRING} Display an error if unset.

BRACE EXPANSION

Ranges

# Syntax: {<START>..<END>}

# Print numbers 1-100.
echo {1..100}

# Print range of floats.
echo 1.{1..9}

# Print chars a-z.
echo {a..z}
echo {A..Z}

# Nesting.
echo {A..Z}{0..9}

# Print zero-padded numbers.
# CAVEAT: bash 4+
echo {01..100}

# Change increment amount.
# Syntax: {<START>..<END>..<INCREMENT>}
# CAVEAT: bash 4+
echo {1..10..2} # Increment by 2.

String Lists

echo {apples,oranges,pears,grapes}

# Example Usage:
# Remove dirs Movies, Music and ISOS from ~/Downloads/.
rm -rf ~/Downloads/{Movies,Music,ISOS}

CONDITIONAL EXPRESSIONS

File Conditionals

Expression Value What does it do?
-a file If file exists.
-b file If file exists and is a block special file.
-c file If file exists and is a character special file.
-d file If file exists and is a directory.
-e file If file exists.
-f file If file exists and is a regular file.
-g file If file exists and its set-group-id bit is set.
-h file If file exists and is a symbolic link.
-k file If file exists and its sticky-bit is set
-p file If file exists and is a named pipe (FIFO).
-r file If file exists and is readable.
-s file If file exists and its size is greater than zero.
-t fd If file descriptor is open and refers to a terminal.
-u file If file exists and its set-user-id bit is set.
-w file If file exists and is writable.
-x file If file exists and is executable.
-G file If file exists and is owned by the effective group ID.
-L file If file exists and is a symbolic link.
-N file If file exists and has been modified since last read.
-O file If file exists and is owned by the effective user ID.
-S file If file exists and is a socket.

File Comparisons

Expression What does it do?
file -ef file2 If both files refer to the same inode and device numbers.
file -nt file2 If file is newer than file2 (uses modification time) or file exists and file2 does not.
file -ot file2 If file is older than file2 (uses modification time) or file2 exists and file does not.

Variable Conditionals

Expression Value What does it do?
-o opt If shell option is enabled.
-v var If variable has a value assigned.
-R var If variable is a name reference.
-z var If the length of string is zero.
-n var If the length of string is non-zero.

Variable Comparisons

Expression What does it do?
var = var2 Equal to.
var == var2 Equal to (synonym for =).
var != var2 Not equal to.
var < var2 Less than (in ASCII alphabetical order.)
var > var2 Greater than (in ASCII alphabetical order.)

ARITHMETIC OPERATORS

Assignment

Operators What does it do?
= Initialize or change the value of a variable.

Arithmetic

Operators What does it do?
+ Addition
- Subtraction
* Multiplication
/ Division
** Exponentiation
% Modulo
+= Plus-Equal (Increment a variable.)
-= Minus-Equal (Decrement a variable.)
*= Times-Equal (Multiply a variable.)
/= Slash-Equal (Divide a variable.)
%= Mod-Equal (Remainder of dividing a variable.)

Bitwise

Operators What does it do?
<< Bitwise Left Shift
<<= Left-Shift-Equal
>> Bitwise Right Shift
>>= Right-Shift-Equal
& Bitwise AND
&= Bitwise AND-Equal
| Bitwise OR
|= Bitwise OR-Equal
~ Bitwise NOT
^ Bitwise XOR
^= Bitwise XOR-Equal

Logical

Operators What does it do?
! NOT
&& AND
|| OR

Miscellaneous

Operators What does it do? Example
, Comma Separator ((a=1,b=2,c=3))

ARITHMETIC

Simpler syntax to set variables

# Simple math
((var=1+2))

# Decrement/Increment variable
((var++))
((var--))
((var+=1))
((var-=1))

# Using variables
((var=var2*arr[2]))

Ternary Tests

# Set the value of var to var2 if var2 is greater than var.
# var: variable to set.
# var2>var: Condition to test.
# ?var2: If the test succeeds.
# :var: If the test fails.
((var=var2>var?var2:var))

TRAPS

Traps allow a script to execute code on various signals. In pxltrm (a pixel art editor written in bash) traps are used to redraw the user interface on window resize. Another use case is cleaning up temporary files on script exit.

Traps should be added near the start of scripts so any early errors are also caught.

NOTE: For a full list of signals, see trap -l.

Do something on script exit

# Clear screen on script exit.
trap 'printf \\e[2J\\e[H\\e[m' EXIT

Ignore terminal interrupt (CTRL+C, SIGINT)

trap '' INT

React to window resize

# Call a function on window resize.
trap 'code_here' SIGWINCH

Do something before every command

trap 'code_here' DEBUG

Do something when a shell function or a sourced file finishes executing

trap 'code_here' RETURN

PERFORMANCE

Disable Unicode

If unicode is not required, it can be disabled for a performance increase. Results may vary however there have been noticeable improvements in neofetch and other programs.

# Disable unicode.
LC_ALL=C
LANG=C

OBSOLETE SYNTAX

Shebang

Use #!/usr/bin/env bash instead of #!/bin/bash.

  • The former searches the user's PATH to find the bash binary.
  • The latter assumes it is always installed to /bin/ which can cause issues.

NOTE: There are times when one may have a good reason for using #!/bin/bash or another direct path to the binary.

# Right:

    #!/usr/bin/env bash

# Less right:

    #!/bin/bash

Command Substitution

Use $() instead of ` `.

# Right.
var="$(command)"

# Wrong.
var=`command`

# $() can easily be nested whereas `` cannot.
var="$(command "$(command)")"

Function Declaration

Do not use the function keyword, it reduces compatibility with older versions of bash.

# Right.
do_something() {
    # ...
}

# Wrong.
function do_something() {
    # ...
}

INTERNAL VARIABLES

Get the location to the bash binary

"$BASH"

Get the version of the current running bash process

# As a string.
"$BASH_VERSION"

# As an array.
"${BASH_VERSINFO[@]}"

Open the user's preferred text editor

"$EDITOR" "$file"

# NOTE: This variable may be empty, set a fallback value.
"${EDITOR:-vi}" "$file"

Get the name of the current function

# Current function.
"${FUNCNAME[0]}"

# Parent function.
"${FUNCNAME[1]}"

# So on and so forth.
"${FUNCNAME[2]}"
"${FUNCNAME[3]}"

# All functions including parents.
"${FUNCNAME[@]}"

Get the host-name of the system

"$HOSTNAME"

# NOTE: This variable may be empty.
# Optionally set a fallback to the hostname command.
"${HOSTNAME:-$(hostname)}"

Get the architecture of the Operating System

"$HOSTTYPE"

Get the name of the Operating System / Kernel

This can be used to add conditional support for different Operating Systems without needing to call uname.

"$OSTYPE"

Get the current working directory

This is an alternative to the pwd built-in.

"$PWD"

Get the number of seconds the script has been running

"$SECONDS"

Get a pseudorandom integer

Each time $RANDOM is used, a different integer between 0 and 32767 is returned. This variable should not be used for anything related to security (this includes encryption keys etc).

"$RANDOM"

INFORMATION ABOUT THE TERMINAL

Get the terminal size in lines and columns (from a script)

This is handy when writing scripts in pure bash and stty/tput can’t be called.

Example Function:

get_term_size() {
    # Usage: get_term_size

    # (:;:) is a micro sleep to ensure the variables are
    # exported immediately.
    shopt -s checkwinsize; (:;:)
    printf '%s\n' "$LINES $COLUMNS"
}

Example Usage:

# Output: LINES COLUMNS
$ get_term_size
15 55

Get the terminal size in pixels

CAVEAT: This does not work in some terminal emulators.

Example Function:

get_window_size() {
    # Usage: get_window_size
    printf '%b' "${TMUX:+\\ePtmux;\\e}\\e[14t${TMUX:+\\e\\\\}"
    IFS=';t' read -d t -t 0.05 -sra term_size
    printf '%s\n' "${term_size[1]}x${term_size[2]}"
}

Example Usage:

# Output: WIDTHxHEIGHT
$ get_window_size
1200x800

# Output (fail):
$ get_window_size
x

Get the current cursor position

This is useful when creating a TUI in pure bash.

Example Function:

get_cursor_pos() {
    # Usage: get_cursor_pos
    IFS='[;' read -p $'\e[6n' -d R -rs _ y x _
    printf '%s\n' "$x $y"
}

Example Usage:

# Output: X Y
$ get_cursor_pos
1 8

CONVERSION

Convert a hex color to RGB

Example Function:

hex_to_rgb() {
    # Usage: hex_to_rgb "#FFFFFF"
    #        hex_to_rgb "000000"
    : "${1/\#}"
    ((r=16#${_:0:2},g=16#${_:2:2},b=16#${_:4:2}))
    printf '%s\n' "$r $g $b"
}

Example Usage:

$ hex_to_rgb "#FFFFFF"
255 255 255

Convert an RGB color to hex

Example Function:

rgb_to_hex() {
    # Usage: rgb_to_hex "r" "g" "b"
    printf '#%02x%02x%02x\n' "$1" "$2" "$3"
}

Example Usage:

$ rgb_to_hex "255" "255" "255"
#FFFFFF

CODE GOLF

Shorter for loop syntax

# Tiny C Style.
for((;i++<10;)){ echo "$i";}

# Undocumented method.
for i in {1..10};{ echo "$i";}

# Expansion.
for i in {1..10}; do echo "$i"; done

# C Style.
for((i=0;i<=10;i++)); do echo "$i"; done

Shorter infinite loops

# Normal method
while :; do echo hi; done

# Shorter
for((;;)){ echo hi;}

Shorter function declaration

# Normal method
f(){ echo hi;}

# Using a subshell
f()(echo hi)

# Using arithmetic
# This can be used to assign integer values.
# Example: f a=1
#          f a++
f()(($1))

# Using tests, loops etc.
# NOTE: ‘while’, ‘until’, ‘case’, ‘(())’, ‘[[]]’ can also be used.
f()if true; then echo "$1"; fi
f()for i in "$@"; do echo "$i"; done

Shorter if syntax

# One line
# Note: The 3rd statement may run when the 1st is true
[[ $var == hello ]] && echo hi || echo bye
[[ $var == hello ]] && { echo hi; echo there; } || echo bye

# Multi line (no else, single statement)
# Note: The exit status may not be the same as with an if statement
[[ $var == hello ]] &&
    echo hi

# Multi line (no else)
[[ $var == hello ]] && {
    echo hi
    # ...
}

Simpler case statement to set variable

The : built-in can be used to avoid repeating variable= in a case statement. The $_ variable stores the last argument of the last command. : always succeeds so it can be used to store the variable value.

# Modified snippet from Neofetch.
case "$OSTYPE" in
    "darwin"*)
        : "MacOS"
    ;;

    "linux"*)
        : "Linux"
    ;;

    *"bsd"* | "dragonfly" | "bitrig")
        : "BSD"
    ;;

    "cygwin" | "msys" | "win32")
        : "Windows"
    ;;

    *)
        printf '%s\n' "Unknown OS detected, aborting..." >&2
        exit 1
    ;;
esac

# Finally, set the variable.
os="$_"

REAL IMPLEMENTATION

A custom Neovim Config script

  • Example of using the Simpler case statement to set variable

  • And

  • Shorter for loop syntax - C-Style

#!/usr/bin/env bash

install_prompt() {
        # Acceptable inputs: yes, y, no, n and Enter1
        read -r -p "Ready to install the new Neovim configuration? (yes/no) or hit Enter: " confirm
        confirm=${confirm:"yes"}
        confirm=$(echo "$confirm" | tr '[:upper:]' '[:lower:]')
        if [[ "$confirm" != "yes" && "$confirm" != "y" ]]; then
            printf "\e[1;31m[-] Exiting installation.\e[0m\n"
            exit 1
        fi
}

# Detect operating system, either macOS or Linux
get_os() {
    case "$(uname -s)" in
        "Darwin")
            # Get macOS version
            darwin_version=$(sw_vers -productVersion)
            case "$darwin_version" in
                16.*) OS="Tahoe" ;;
                15.*) OS="Sequoia" ;;
                14.*) OS="Sonoma" ;;
                13.*) OS="Ventura" ;;
                12.*) OS="Monterey" ;;
                *)    OS="macOS" ;;
            esac
        ;;
        "Linux")
            OS="Linux"  # Directly set OS to "Linux"
        ;;
        *BSD|DragonFly|Bitrig)
            OS="BSD"    # Directly set OS to "BSD"
        ;;
        *)
            printf "\e[1;31m[-] Unknown OS detected: '%s', aborting...\e[0m\n" "$(uname -s)" >&2
            exit 1
        ;;
    esac

    # No need for $_ here, OS is already set
    printf "\e[1;32m[+] Detected OS: %s\e[0m\n" "$OS"
}

# Check for macOS first
detect_distro() {
        # Define an array of supported macOS versions
        local mac_vers=("Tahoe" "Sequoia" "Sonoma" "Ventura" "Monterey" "macOS")
        local is_macos_version=false

        for ((i=0;i<${#mac_vers[@]};i++)); do
            if [ "$OS" = "${mac_vers[$i]}" ]; then
                is_macos_version=true
                break
            fi
        done

        if [ "$is_macos_version" = true ]; then
            DISTRO="$OS"

            # Check if Homebrew is installed
            if command -v brew &> /dev/null; then
                PKG_MANAGER="brew"
            else
                printf "\e[1;33m[!] Homebrew is not installed on your macOS system.\e[0m\n"
                printf "\e[1;34m[?] Would you like to install Homebrew? (yes/no): \e[0m"
                read -r -p "" install_brew
                install_brew=${install_brew:-"no"}
                install_brew=$(echo "$install_brew" | tr '[:upper:]' '[:lower:]')
                if [[ "$install_brew" == "yes" || "$install_brew" == "y" ]]; then
                    printf "\e[1;34m[+] Installing Homebrew...\e[0m\n"
                    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
                    PKG_MANAGER="brew"
                else
                    printf "\e[1;31m[-] Homebrew is required for package management on macOS. Exiting.\e[0m\n"
                    exit 1
                fi
            fi
            printf "\e[1;32m[+] Detected macOS: %s (Package Manager: %s)\e[0m\n" "$DISTRO" "$PKG_MANAGER"
            return
        fi

        # Attempt to get distribution info from os-release file
        if [ -f /etc/os-release ]; then
            . /etc/os-release
            DISTRO="$NAME"
        # Then check specific distribution files in a consistent order
        elif [ -f /etc/lsb-release ]; then
            . /etc/lsb-release
            DISTRO="$DISTRIB_ID"
        elif [ -f /etc/debian_version ]; then
            DISTRO="Debian"
        elif [ -f /etc/ubuntu_version ]; then
            DISTRO="Ubuntu"
        elif [ -f /etc/fedora-release ]; then
            DISTRO="Fedora"
        elif [ -f /etc/redhat-release ]; then
            DISTRO="Red Hat"
        elif [ -f /etc/centos-release ]; then
            DISTRO="CentOS"
        elif [ -f /etc/arch-release ]; then
            DISTRO="Arch"
        elif [ -f /etc/alpine-release ]; then
            DISTRO="Alpine"
        elif [ -f /etc/opensuse-release ]; then
            DISTRO="openSUSE"  # Standardized capitalization
        elif [ -f /etc/void-release ]; then
            DISTRO="Void"
        elif uname -s | grep -q "FreeBSD"; then
            DISTRO="FreeBSD"
        else
            printf "\e[1;31m[-] Unsupported Linux distribution.\e[0m\n"
            exit 1
        fi

        # Determine package manager based on distribution
        case "$DISTRO" in
            "Debian"* | "Ubuntu"*)
                PKG_MANAGER="apt"
            ;;
            "Fedora"*)
                PKG_MANAGER="dnf"
            ;;
            "Red Hat"* | "CentOS"*)
                PKG_MANAGER="dnf"
            ;;
            "Arch"*)
                PKG_MANAGER="pacman"
            ;;
            "Alpine"*)
                PKG_MANAGER="apk"
            ;;
            "openSUSE"*)
                PKG_MANAGER="zypper"
            ;;
            "Void"*)
                PKG_MANAGER="xbps"
            ;;
            "FreeBSD"*)
                PKG_MANAGER="pkg"
            ;;
            *)
                printf "\e[1;31m[-] Unsupported Linux distribution.\e[0m\n"
                exit 1
            ;;
        esac

        printf "\e[1;32m[+] Detected distribution: %s (Package Manager: %s)\e[0m\n" "$DISTRO" "$PKG_MANAGER"
}

full_sys_upgrade() {
    # Based on the detected distribution, perform a full system upgrade using that distribution's package manager
    case "$PKG_MANAGER" in
                "apt")
                    : "sudo apt update && sudo apt upgrade -y"
                ;;
                "dnf")
                    : "sudo dnf update -y"
                ;;
                "pacman")
                    : "sudo pacman -Syu --noconfirm"
                ;;
                "apk")
                    : "sudo apk update && sudo apk upgrade"
                ;;
                "zypper")
                    : "sudo zypper update -y"
                ;;
                "xbps")
                    : "sudo xbps-install -Su -y"
                ;;
                "pkg")
                    : "sudo pkg update && sudo pkg upgrade -y"
                ;;
                "brew")
                    : "brew update && brew upgrade"
                ;;
                *)
                    printf "\e[1;31m[-] Unsupported package manager: %s\e[0m\n" "$PKG_MANAGER"
                    exit 1
                ;;
    esac

    # Execute the command stored in $_
    eval "$_"
}

check_neovim_version() {
        # Check if nvim is installed first
        if ! command -v nvim &> /dev/null; then
            printf "\e[1;31m[-] Neovim is not installed.\e[0m\n"
            printf "\e[1;34m[?] Would you like to install Neovim? (yes/no): \e[0m"
            read -r -p "" install_nvim
            install_nvim=${install_nvim:-"no"}
            install_nvim=$(echo "$install_nvim" | tr '[:upper:]' '[:lower:]')
            if [[ "$install_nvim" == "yes" || "$install_nvim" == "y" ]]; then
                build_neovim
            else
                printf "\e[1;31m[-] Neovim is required for this configuration. Exiting.\e[0m\n"
                exit 1
            fi
            return
        fi

        # Reliably extract version number
        nvim_version=$(nvim --version | head -n1 | grep -oE '[0-9]+\.[0-9]+\.[0-9]+' || nvim --version | head -n1 | grep -oE '[0-9]+\.[0-9]+')
        required_version="0.9.0"

        # Compare versions using sort -V (version sort)
        if ! printf "%s\n%s\n" "$required_version" "$nvim_version" | sort -V -C; then
            printf "\e[1;31m[-] Neovim version %s or higher is required. Your version: %s\e[0m\n" "$required_version" "$nvim_version"
            printf "\e[1;34m[?] Would you like to build the latest Neovim from source? (yes/no): \e[0m"
            read -r -p "" build_source
            build_source=${build_source:-"no"}
            build_source=$(echo "$build_source" | tr '[:upper:]' '[:lower:]')
            if [[ "$build_source" == "yes" || "$build_source" == "y" ]]; then
                build_neovim
            else
                printf "\e[1;31m[-] A newer version of Neovim is required. Exiting.\e[0m\n"
                exit 1
            fi
        else
            printf "\e[1;32m[+] Neovim version check passed: %s\e[0m\n" "$nvim_version"
        fi
}

build_neovim() {
        printf "\e[1;34m[+] Building Neovim from source...\e[0m\n"

        # Check if existing Neovim should be removed
        if command -v nvim &> /dev/null; then
            printf "\e[1;34m[?] Remove existing Neovim installation? (yes/no): \e[0m"
            read -r -p "" remove_existing
            remove_existing=${remove_existing:-"no"}
            remove_existing=$(echo "$remove_existing" | tr '[:upper:]' '[:lower:]')
            if [[ "$remove_existing" =~ ^(yes|y)$ ]]; then
                echo "Removing existing Neovim installation..."
                # Complete removal: remove all previous neovim files and directories & purge
                case "$PKG_MANAGER" in
                    "apt")
                        : "sudo apt remove -y neovim && sudo apt purge -y --autoremove neovim"
                    ;;
                    "dnf")
                        : "sudo dnf remove -y neovim && sudo dnf autoremove -y"
                    ;;
                    "pacman")
                        : "sudo pacman -Rns --noconfirm neovim"
                    ;;
                    "apk")
                        : "sudo apk del neovim"
                    ;;
                    "pkg")
                        : "sudo pkg delete -y neovim"
                    ;;
                    "zypper") # openSUSE
                        : "sudo zypper remove -y --clean-deps neovim"
                    ;;
                    "xbps") # Void Linux
                        : "sudo xbps-remove -R -y neovim"
                    ;;
                    "brew") # macOS with Homebrew
                        : "brew remove neovim"
                    ;;
                    *)
                        printf "\e[1;31m[-] Unsupported package manager: %s\e[0m\n" "$PKG_MANAGER"
                        exit 1
                    ;;
                esac

                # Execute the command stored in $_
                eval "$_"
            fi
        fi

        # Install Neovim build prerequisites
        printf "\e[1;34m[+] Installing Neovim build dependencies...\e[0m\n"
        case "$PKG_MANAGER" in
            "apt") # Debian/Ubuntu & debian-based systems
                : "sudo apt install -y ninja-build gettext cmake unzip curl build-essential"
            ;;
            "dnf") # RHEL/Fedora
                : "sudo dnf -y install ninja-build cmake gcc make gettext curl glibc-gconv-extra"
            ;;
            "pacman") # Arch Linux
                : "sudo pacman -S base-devel cmake ninja curl"
            ;;
            "apk") # Alpine Linux
                : "apk add build-base cmake coreutils curl gettext-tiny-dev"
            ;;
            "zypper") # openSUSE
                : "sudo zypper install ninja cmake gcc-c++ gettext-tools curl"
            ;;
            "xbps") # Void Linux
                : "xbps-install base-devel cmake curl git"
            ;;
            "pkg") # FreeBSD
                : "sudo pkg install cmake gmake sha wget gettext curl"
            ;;
            "brew") # macOS with Homebrew
                : "brew install ninja cmake gettext curl"
            ;;
            *)
                printf "\e[1;31m[-] Unsupported package manager: %s\e[0m\n" "$PKG_MANAGER"
                exit 1
            ;;
        esac

        # Execute the command
        eval "$_"

        # Create a temporary directory for building Neovim
        build_dir=$(mktemp -d)
        if ! build_dir=$(mktemp -d); then
            printf "\e[1;31m[-] Failed to create temporary directory for building Neovim.\e[0m\n"
            exit 1
        fi

        # Ensure clean up after build
        trap 'rm -rf "$build_dir"' EXIT

        # Clone Neovim repository
        cd "$build_dir" || {
            printf "\e[1;31m[-] Failed to change directory to %s.\e[0m\n" "$build_dir"
            exit 1
        }

        if ! git clone https://github.com/neovim/neovim.git; then
            printf "\e[1;31m[-] Failed to clone Neovim repository.\e[0m\n"
            exit 1
        fi

        cd neovim || {
            printf "\e[1;31m[-] Failed to change directory to neovim.\e[0m\n"
            exit 1
        }

        # Checkout the stable branch
        if ! git checkout stable; then
            printf "\e[1;31m[-] Failed to checkout stable branch.\e[0m\n"
            exit 1
        fi

        # Build Neovim with parallel jobs
        printf "\e[1;34m[+] Building Neovim (this may take a while)...\e[0m\n"
        if ! make -j"$(nproc)" CMAKE_BUILD_TYPE=RelWithDebInfo; then
            printf "\e[1;31m[-] Failed to build Neovim.\e[0m\n"
            exit 1
        fi

        # Install Neovim
        printf "\e[1;34m[+] Installing Neovim...\e[0m\n"
        if ! sudo make install; then
            printf "\e[1;31m[-] Failed to install Neovim.\e[0m\n"
            exit 1
        fi

        # Create a symbolic link for Neovim if it doesn't exist
        if [ ! -f /usr/bin/nvim ]; then
            sudo ln -sf /usr/local/bin/nvim /usr/bin/nvim
        fi

        printf "\e[1;32m[+] Neovim built and installed successfully.\e[0m\n"

        # Verify the installation
        nvim_version=$(nvim --version | head -n1)
        printf "\e[1;32m[+] Installed: %s\e[0m\n" "$nvim_version"
}


install_nvim_config_deps(){
         printf "\e[1;34m[+] Installing the custom configuration dependencies for %s using %s...\e[0m\n" "$DISTRO" "$PKG_MANAGER"

         case "$PKG_MANAGER" in
             "apt")
                 : "sudo apt update && sudo apt install -y tree-sitter tree-sitter-cli nodejs npm shellcheck ripgrep"
                 ;;
             "dnf")
                 : "sudo dnf update -y && sudo dnf install -y tree-sitter tree-sitter-cli nodejs npm ripgrep"
                 ;;
             "pacman")
                 : "sudo pacman -S --noconfirm tree-sitter tree-sitter-cli nodejs npm shellcheck ripgrep"
                 ;;
             "apk")
                 : "sudo apk add --no-cache -y tree-sitter tree-sitter-cli nodejs npm shellcheck ripgrep"
                 ;;
             "pkg")
                 : "sudo pkg install -y tree-sitter tree-sitter-cli nodejs npm shellcheck ripgrep"
                 ;;
             "zypper")
                 : "sudo zypper install -y tree-sitter tree-sitter-cli nodejs npm shellcheck ripgrep"
                 ;;
             "xbps")
                 : "sudo xbps-install -S -y tree-sitter tree-sitter-cli nodejs npm shellcheck ripgrep"
                 ;;
             "brew") # macOS with Homebrew
                 : "brew install tree-sitter node shellcheck ripgrep"
                 ;;
             *)
                 printf "\e[1;31m[-] Unsupported package manager: %s\e[0m\n" "$PKG_MANAGER"
                 exit 1
                 ;;
         esac

         # Execute the command stored in $_
           eval "$_"
}
# Removing your old Neovim config to install the new one
remove_old_config() {
        printf "\e[1;34m[+] Removing old Neovim configuration...\e[0m\n"
        rm -rf ~/.config/nvim; rm -rf ~/.local/share/nvim
        sleep 2
}


# Function to make the nvim directory if it doesn't exist in ~/.config/nvim
# mkdir -p ~/.config/nvim
mk_nvim_dir() {
        mkdir -p "${XDG_CONFIG_HOME:-$HOME/.config}"/nvim
        # check that the directory was created
        if [ -d "${XDG_CONFIG_HOME:-$HOME/.config}"/nvim ]; then
                printf "\e[1;32m[+] Neovim configuration directory created successfully.\e[0m\n"
        else
            # Force a manual creation of the directory if it doesn't exist
            # prompt user to enter mkdir -p ~/.config/nvim
            printf "\e[1;31m[-] Failed to create Neovim configuration directory.\e[0m\n"
            printf "\e[1;31mPlease run the following commands manually:\e[0m\n"
            printf "\e[1;31m    mkdir -p ~/.config/nvim\e[0m\n"
            printf "\e[1;31mThen continue with the custom config installation:\e[0m\n"
            printf "\e[1;31m    git clone https://github.com/LinuxUser255/nvim.git ~/.config/nvim\e[0m\n"
            exit 1
        fi
}

# Git clone the Neovim configuration repo
install_config() {
        printf "\e[1;34m[+] Git cloning new config. Open Neovim to install plugins...\e[0m\n"

        # Create the directory
        mkdir -p "${XDG_CONFIG_HOME:-$HOME/.config}"/nvim

        # Clone the repository
        if ! git clone https://github.com/LinuxUser255/nvim.git "${XDG_CONFIG_HOME:-$HOME/.config}"/nvim; then
            printf "\e[1;31m[-] Failed to clone the configuration repository.\e[0m\n"
            printf "\e[1;31m    The directory might not be empty. Try running the script again.\e[0m\n"
            exit 1
        fi

        printf "\e[1;32m[+] Configuration cloned successfully.\e[0m\n"
}

main() {
        install_prompt
        get_os
        detect_distro
        full_sys_upgrade
        check_neovim_version  # This will call build_neovim if needed
        install_nvim_config_deps
        remove_old_config  # Then remove old config (this will recreate the directory)
        install_config
}

main

OTHER

Use read as an alternative to the sleep command

Surprisingly, sleep is an external command and not a bash built-in.

CAVEAT: Requires bash 4+

Example Function:

read_sleep() {
    # Usage: read_sleep 1
    #        read_sleep 0.2
    read -rt "$1" <> <(:) || :
}

Example Usage:

read_sleep 1
read_sleep 0.1
read_sleep 30

For performance-critical situations, where it is not economic to open and close an excessive number of file descriptors, the allocation of a file descriptor may be done only once for all invocations of read:

(See the generic original implementation at https://blog.dhampir.no/content/sleeping-without-a-subprocess-in-bash-and-how-to-sleep-forever)

exec {sleep_fd}<> <(:)
while some_quick_test; do
    # equivalent of sleep 0.001
    read -t 0.001 -u $sleep_fd
done

Check if a program is in the user's PATH

# There are 3 ways to do this and either one can be used.
type -p executable_name &>/dev/null
hash executable_name &>/dev/null
command -v executable_name &>/dev/null

# As a test.
if type -p executable_name &>/dev/null; then
    # Program is in PATH.
fi

# Inverse.
if ! type -p executable_name &>/dev/null; then
    # Program is not in PATH.
fi

# Example (Exit early if program is not installed).
if ! type -p convert &>/dev/null; then
    printf '%s\n' "error: convert is not installed, exiting..."
    exit 1
fi

Get the current date using strftime

Bash’s printf has a built-in method of getting the date which can be used in place of the date command.

CAVEAT: Requires bash 4+

Example Function:

date() {
    # Usage: date "format"
    # See: 'man strftime' for format.
    printf "%($1)T\\n" "-1"
}

Example Usage:

# Using above function.
$ date "%a %d %b  - %l:%M %p"
Fri 15 Jun  - 10:00 AM

# Using printf directly.
$ printf '%(%a %d %b  - %l:%M %p)T\n' "-1"
Fri 15 Jun  - 10:00 AM

# Assigning a variable using printf.
$ printf -v date '%(%a %d %b  - %l:%M %p)T\n' '-1'
$ printf '%s\n' "$date"
Fri 15 Jun  - 10:00 AM

Get the username of the current user

CAVEAT: Requires bash 4.4+

$ : \\u
# Expand the parameter as if it were a prompt string.
$ printf '%s\n' "${_@P}"
black

Generate a UUID V4

CAVEAT: The generated value is not cryptographically secure.

Example Function:

uuid() {
    # Usage: uuid
    C="89ab"

    for ((N=0;N<16;++N)); do
        B="$((RANDOM%256))"

        case "$N" in
            6)  printf '4%x' "$((B%16))" ;;
            8)  printf '%c%x' "${C:$RANDOM%${#C}:1}" "$((B%16))" ;;

            3|5|7|9)
                printf '%02x-' "$B"
            ;;

            *)
                printf '%02x' "$B"
            ;;
        esac
    done

    printf '\n'
}

Example Usage:

$ uuid
d5b6c731-1310-4c24-9fe3-55d556d44374

Progress bars

This is a simple way of drawing progress bars without needing a for loop in the function itself.

Example Function:

bar() {
    # Usage: bar 1 10
    #            ^----- Elapsed Percentage (0-100).
    #               ^-- Total length in chars.
    ((elapsed=$1*$2/100))

    # Create the bar with spaces.
    printf -v prog  "%${elapsed}s"
    printf -v total "%$(($2-elapsed))s"

    printf '%s\r' "[${prog// /-}${total}]"
}

Example Usage:

for ((i=0;i<=100;i++)); do
    # Pure bash micro sleeps (for the example).
    (:;:) && (:;:) && (:;:) && (:;:) && (:;:)

    # Print the bar.
    bar "$i" "10"
done

printf '\n'

Get the list of functions in a script

get_functions() {
    # Usage: get_functions
    IFS=$'\n' read -d "" -ra functions < <(declare -F)
    printf '%s\n' "${functions[@]//declare -f }"
}

Bypass shell aliases

# alias
ls

# command
# shellcheck disable=SC1001
\ls

Bypass shell functions

# function
ls

# command
command ls

Run a command in the background

This will run the given command and keep it running, even after the terminal or SSH connection is terminated. All output is ignored.

bkr() {
    (nohup "$@" &>/dev/null &)
}

bkr ./some_script.sh # some_script.sh is now running in the background

Capture the return value of a function without command substitution

CAVEAT: Requires bash 4+

This uses local namerefs to avoid using var=$(some_func) style command substitution for function output capture.

to_upper() {
  local -n ptr=${1}

  ptr=${ptr^^}
}

foo="bar"
to_upper foo
printf "%s\n" "${foo}" # BAR

AFTERWORD

Thanks for reading! If this bible helped you in any way and you'd like to give back, consider donating. Donations give me the time to make this the best resource possible. Can't donate? That's OK, star the repo and share it with your friends!

Rock on. 🤘

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📖 A collection of pure bash alternatives to external processes. I'm adding extra code snippets to the README

Topics

macos linux bash cli neofetch shell-script bash-script shell-scripting bash-scripting posix-compliant neofetch-clone

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