Extended Bash Library

What is?

Extended Bash Library is a superset for the bash shell! This superset aims to create a more readable shell script and add functionality inspired by other languages, such as pyhton and javascript.

Some methods have been adapted from javascript that work in a similar way, such as:

• arrayMap(): works similar to Array.map, but does not return an array
• arrayFilter(): works with syntax and behavior similar to array.filter, but the penultimate argument must be the NAME of the return array
• forEach(), a function that at each iteration points a reference to the current item in an array

From python:

• len(), returns to stdout the size of an array, the size of a string passed by reference, or a simple string
• Split(), has the same behavior as python's split() method

Curiosity

Previously the library was called "Common Shell Library", but from now on ( 07/28/2022 ) it is called "Extended Bash Library"
"Extended Bash Library" name was inspired by the extended family of filesystems (ext2, ext3, ext4)...

Pseudo keywords

Bash does not have these keywords, but aliases have been created to make it easier to declare certain types

• int, declare variable with 'integer' attribute
• dict, declare variable as associative array
• newPtr, declare variable as reference to named variable

Considerations about scope of variables:

When using these pseudotypes in a function, the variables are locally scoped!
To declare them as global variables, add the -g parameter
Local variables are visible to the function in which they are defined, as well as their children¹

Example:

f(){
	# Makes X a global variable
	int -g X=0
	# Makes NAMES a global variable
	dict -g NAMES=()
}
f

Advantages

Rapid development of installation and configuration scripts using WriterFileln function families
Support for referencing variables using the newPtr keyword (alias to declare -n)

• Easy development of installers for debian systems, using custom APT functions
• Facilitates repository configuration, using the function
• Import some concepts and facilities from python and javascripts to bash
• It is a library that has passed unit tests!!

Functions

Note: a shell function is declared by Name(){COMMANDS;} or function Name{ COMMANDS;} Each argument is referenced by $1..$n.

The list below includes the parameters within the parentheses for teaching purposes.

• replaceLine(file,string_to_find,string_to_replace)
• deleteLine(file,line_to_delete)
• scappeString(str)//
• AptInstall(packages) //install apt packages

New: String manipulation functions

• strLen(str) //returns to output of length of string, a equivalent C strlen()
• strGetSubstring(str,offset,length) // returns to output a str delimeted of offset and lenght
• strGetCurrentChar(str,index) //returns to output a char delimited by index, a equivalent C str[index];
• Split(str,delimiter,ref_array) // split (using a builtin command) a string and store in ref_array ( ref_array is a reference to array )
• splitStr(str,delimiter,ref_array) split a string and store in ref_array

New: Array Functions

Important note!!

In array functions the command must be enclosed in single quotes:

• arrayMap(array,item, '{commands...}') // executes 'one or more commands' on each item in an array.
• arrayFilter(array, item, filteredItems, '[conditions]')
• arrayToString(array)
• arraySlice(array,offset,arraySliced) || arraySlice(array,offset,length,arraySliced)
• forEach(array,item '{commands...}') //execute one or more commands, on each item in array, forEach is a function similar to arrayMap, but the iterator is a reference to the current element of the array
• initArrayAsCommand(array, '{commands'}) //init an array as output of '{ commands }'

New: APT functions

This family call APT functions with -y and check erros param

• AptInstall(args...) #install packages without need confirm action
• getCurrentDebianFrontend() # set (if is possible) DEBIAN_FRONTEND=
• getAptKeys(array_key_ref) # import apt keys to Apt from array of Urls: note
• getDebPackVersion # returns a version of package (.deb) installed
• ConfigureSourcesListByScript(scripts_url) configure sources from array of url scripts (apt)
• ConfigureSourcesList(repository, mirrors,apt_keys), configure sources

Samples:

len function

Note: The len function can determine to infer the type of argument, if it is the name of a variable or a simple string

A length of ${#names[@]}

unset names
names=({1..20..2})
len names 

A lenght of ${#names}

unset names
names='Davros' 
# Returns 6 to stdout
len names

Sample return size of 'names' string

unset names
# Returns 5 to stdout
len names 

sample: Splitting a string

source ./extended-bash.sh
#split a string delimeted by ' ' (blank space)
my_array=()
str="Hello World!"
Split "$str" " " my_array # my_array=("Hello" "World!")

sample: Getting a substring using a offset and length

source ./extended-bash.sh
str="user@pc:~"
sub_str="$(strGetSubstring "$str" 5 2)" #sub_str="pc"

sample: Installing packages using arrayMap

source ./extended-bash.sh
packages=(gcc g++ wget)
arrayMap  packages package 'sudo apt-get install $package -y

Notes: packages is array variable package is name to iterator 'sudo apt-get install $package' is a command to execute for each item in packages

sample: Filter pars numbers and store in pars.

source ./extended-bash.sh
numbers=({357..368})
pars=()
arrayFilter numbers number pars '((number %2 == 0))'
#show pars
arrayToString pars

sample: Filter names with start of letter D

source ./extended-bash.sh
names=(Davros Daniel Debra 'Yan Mordock' Woody)
matchD=()
regex_matched_to_d='^D'
arrayFilter names name matchD '[[ "$name" =~ $regex_matched_to_d ]]'

sample: Calculing five times table with forEach

source ./extended-bash.sh
five_times_table=({0..10})
  forEach five_times_table number 'number=$(echo "$number * 5"| bc )'
  arrayMap five_times_table multiple number 'echo "5 * $number = $multiple"' #printing five times table

sample: setting up 3rd party repository quickly

source ./extended-bash.sh

#example: configure google chrome, sublime text and microsoft teams repository!
repositorys=(
	"/etc/apt/sources.list.d/google-chrome.list"
	"/etc/apt/sources.list.d/sublime-text.list"
	"/etc/apt/sources.list.d/geogebra.list"
	"/etc/apt/sources.list.d/teams.list")

mirrors=(
	'deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main' 
	'deb https://download.sublimetext.com/ apt/stable/' 
	'deb http://www.geogebra.net/linux/ stable main'   
	"deb [arch=amd64] https://packages.microsoft.com/repos/ms-teams stable main")

apt_key_url_repository=(
	"https://dl-ssl.google.com/linux/linux_signing_key.pub"
	"https://static.geogebra.org/linux/office@geogebra.org.gpg.key"
	"https://packages.microsoft.com/keys/microsoft.asc")

# Note: requires admin
ConfigureSourcesList apt_key_url_repository mirrors repositorys

sample: setting repository by url script download

source ./extended-bash.sh
# Configuring nodejs repository sample
scripts_url=(
  https://deb.nodesource.com/setup_lts.x 
)
ConfigureSourcesListByScript scripts_url #note requires admin 

References

1 Bash Manual.