Update bash help:

- use snake case
- fix examples
- add notes to expansions

bash.html.markdown

@@ -18,6 +18,7 @@ contributors:
     - ["Harry Mumford-Turner", "https://github.com/harrymt"]
     - ["Martin Nicholson", "https://github.com/mn113"]
     - ["Mark Grimwood", "https://github.com/MarkGrimwood"]
+    - ["Emily Grace Seville", "https://github.com/EmilySeville7cfg"]
 filename: LearnBash.sh
 translators:
     - ["Dimitri Kokkonis", "https://github.com/kokkonisd"]
@@ -37,67 +38,68 @@ or executed directly in the shell.
 # As you already figured, comments start with #. Shebang is also a comment.
 
 # Simple hello world example:
-echo Hello world! # => Hello world!
+echo "Hello world!" # => Hello world!
 
 # Each command starts on a new line, or after a semicolon:
-echo 'This is the first line'; echo 'This is the second line'
+echo "This is the first command"; echo "This is the second command"
-# => This is the first line
+# => This is the first command 
-# => This is the second line
+# => This is the second command 
 
 # Declaring a variable looks like this:
-Variable="Some string"
+variable="Some string"
 
 # But not like this:
-Variable = "Some string" # => returns error "Variable: command not found"
+variable = "Some string" # => returns error "variable: command not found"
-# Bash will decide that Variable is a command it must execute and give an error
+# Bash will decide that `variable` is a command it must execute and give an error
 # because it can't be found.
 
 # Nor like this:
-Variable= 'Some string' # => returns error: "Some string: command not found"
+variable= "Some string" # => returns error: "Some string: command not found"
-# Bash will decide that 'Some string' is a command it must execute and give an
+# Bash will decide that "Some string" is a command it must execute and give an
-# error because it can't be found. (In this case the 'Variable=' part is seen
+# error because it can't be found. In this case the "variable=" part is seen
-# as a variable assignment valid only for the scope of the 'Some string'
+# as a variable assignment valid only for the scope of the "Some string"
-# command.)
+# command.
 
 # Using the variable:
-echo $Variable # => Some string
+echo "$variable" # => Some string
-echo "$Variable" # => Some string
+echo '$variable' # => $variable
-echo '$Variable' # => $Variable
 # When you use the variable itself — assign it, export it, or else — you write
 # its name without $. If you want to use the variable's value, you should use $.
 # Note that ' (single quote) won't expand the variables!
+# You can write variable without surrounding quotes but it's not recommended.
 
-# Parameter expansion ${ }:
+# Parameter expansion ${...}:
-echo ${Variable} # => Some string
+echo "${variable}" # => Some string
-# This is a simple usage of parameter expansion
+# This is a simple usage of parameter expansion such as two examples above.
-# Parameter Expansion gets a value from a variable.
+# Parameter expansion gets a value from a variable.
-# It "expands" or prints the value
+# It "expands" or prints the value.
-# During the expansion time the value or parameter can be modified
+# During the expansion time the value or parameter can be modified.
-# Below are other modifications that add onto this expansion
+# Below are other modifications that add onto this expansion.
 
-# String substitution in variables
+# String substitution in variables:
-echo ${Variable/Some/A} # => A string
+echo "${variable/Some/A}" # => A string
-# This will substitute the first occurrence of "Some" with "A"
+# This will substitute the first occurrence of "Some" with "A".
 
-# Substring from a variable
+# Substring from a variable:
-Length=7
+length=7
-echo ${Variable:0:Length} # => Some st
+echo "${variable:0:length}" # => Some st
 # This will return only the first 7 characters of the value
-echo ${Variable: -5} # => tring
+echo "${variable: -5}" # => tring
-# This will return the last 5 characters (note the space before -5)
+# This will return the last 5 characters (note the space before -5).
+# The space before minus is mandatory here.
 
-# String length
+# String length:
-echo ${#Variable} # => 11
+echo "${#variable}" # => 11
 
-# Indirect expansion
+# Indirect expansion:
-OtherVariable="Variable"
+other_variable="variable"
-echo ${!OtherVariable} # => Some String
+echo ${!other_variable} # => Some string
-# This will expand the value of OtherVariable
+# This will expand the value of `other_variable`.
 
-# Default value for variable
+# Default value for variable:
-echo ${Foo:-"DefaultValueIfFooIsMissingOrEmpty"}
+echo "${foo:-"DefaultValueIfFooIsMissingOrEmpty"}"
 # => DefaultValueIfFooIsMissingOrEmpty
-# This works for null (Foo=) and empty string (Foo=""); zero (Foo=0) returns 0.
+# This works for null (foo=) and empty string (foo=""); zero (foo=0) returns 0.
 # Note that it only returns default value and doesn't change variable value.
 
 # Declare an array with 6 elements