Merge pull request #253 from golergka/bash

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+---
+
+language: bash
+contributors:
+    - ["Max Yankov", "https://github.com/golergka" - "Darren Lin", "https://github.com/CogBear"]
+filename: LearnBash.sh
+
+---
+
+Bash is a name of the unix shell, which was also distributed as the shell for the GNU operating system and as default shell on Linux and Mac OS X.
+Nearly all examples below can be a part of a shell script or executed directly in the shell.
+
+[Read more here.](http://www.gnu.org/software/bash/manual/bashref.html)
+
+```bash
+#!/bin/sh
+# First line of the script is shebang which tells the system how to execute the script: http://en.wikipedia.org/wiki/Shebang_(Unix)
+# As you already figured, comments start with #. Shebang is also a comment.
+
+# Simple hello world example:
+echo Hello, world!
+
+# Each command starts on a new line, or after semicolon:
+echo 'This is the first line'; echo 'This is the second line'
+
+# Declaring a variable looks like this:
+VARIABLE="Some string"
+
+# But not like this:
+VARIABLE = "Some string" # Bash will decide that VARIABLE is a command he must execute and give an error because it couldn't be found.
+
+# Using the variable:
+echo $VARIABLE
+echo "$VARIABLE"
+# When you use the variable itself — assign it, export it, or else — you write it's name without $. If you want to use variable's value, you should use $.
+
+# Reading a value from input:
+echo "What's your name?"
+read NAME # Note that we didn't need to declare new variable
+echo Hello, $NAME!
+
+# We have the usual if structure:
+if true
+then
+	echo "This is expected"
+else
+	echo "And this is not"
+fi
+
+# Expressions are denoted with the following format:
+echo $(( 10 + 5 ))
+
+# Unlike other programming languages, bash is a shell — so it works in a context of current directory.
+# You can list files and directories in the current directories with ls command:
+ls
+
+# These commands have options that control their execution:
+ls -l # Lists every file and directory on a separate line
+
+# Results of the previous command can be passed to the next command as input.
+# grep command filters the input with provided patterns. That's how we can list txt files in the current directory:
+ls -l | grep "\.txt"
+
+# Commands can be substitued within other commands using $( ):
+# The following command displays the number of files and directories in the current directory.
+echo "There are $(ls | wc -l) items here."
+
+#Bash uses a case statement that works similarily to switch in Java and C++:
+case "$VARIABLE"
+in
+	#List patterns for the conditions you want to meet
+	0) echo "There is a zero."
+	1) echo "There is a one."
+	*) echo "It is not null."
+esac
+
+#For loops iterate for as many arguments given:
+#The contents of var $VARIABLE is printed three times.
+for $VARIABLE in x y z
+do
+	echo "$VARIABLE"
+done
+
+```