Black Hat Bash - Bash Scripting for Hackers and Pentesters (Early Access) (Dolev Farhi, Nick Aleks)

#!/bin/bash

PUBLISHER="No Starch Press"

print_name(){

local name

name="Black Hat Bash"

echo "${name} by ${PUBLISHER}"

}

print_name

echo "The variable ${name} will not be printed because it is a local variable."

We assign the value No Starch Press to the variable

publisher, then create a function called print_name(). (

You’ll learn more about functions in the next chapter.) Within the

function, we declare a local variable called name and assign it the

value "Black Hat Bash". Then we call the print_name()

function and attempt to access the name variable as part of a

sentence to be printed using echo.

The echo command at the end of the script file will result in an

empty variable, as the name variable is locally scoped to the

print_name() function, which means that nothing outside of the

function can access it. So, it will simply return without a value.

Save this script, remembering to set the executable permission

using chmod, and run it using the following command:

$ ./local_scope_variable.sh

Black Hat Bash by No Starch Press

The variable will not be printed because it is a local variable.

This script is available at https://github.com/dolevf/Black-Hat-

Bash/blob/master/ch01/local_scope_variable.sh.

Arithmetic Operators

Arithmetic operators allow you to perform mathematical

operations on integers. Table 1-3 shows some of the arithmetic

operators available. The full list of the available arithmetic operators

can be found at https://tldp.org/LDP/abs/html/ops.html.

Table 1-3

Arithmetic Operators

Operator

Description