Added crash course for bash scripting

Signed-off-by: Aakarsh MJ <[email protected]>

Author: ChucklesDroid

Crash Course/cheatsheet.sh

@@ -0,0 +1,140 @@
+#! /usr/bin/bash
+
+#echo "Hello World!"
+# echo Hello World
+
+# Creating Variables
+# Syntax: 
+# a) Capital letters 
+# b) alphabets, numbers and underscores including no-spaces 
+# c) no spaces around the equal sign
+# NAME="Jerry"
+
+# Using Variables
+# Syntax: $variable_name or ${variable_name}
+# echo My name is $NAME
+# echo ${NAME} is a KDE developer
+
+# simple if statement
+# if [ "$NAME" == "Aakarsh" ]
+# then 
+#     echo Your name is $NAME
+# fi
+
+# If-else statement
+# if [ "$NAME" == "Aakarsh" ]
+# then 
+#     echo Your name is Aakarsh
+# else 
+#     echo Yout name is not Aakarsh
+# fi
+
+# else-if statement
+# if [ "$NAME" == "Aakarsh" ]
+# then 
+#     echo Your name is Aakarsh
+# elif [ "$NAME" == "Abhilash" ]
+# then
+#     echo Your name is Abhilash
+# else 
+#     echo Your name is neither Aakarsh or Abhilash
+# fi
+
+# COMPARISIONS 
+# val1 -eq val2 means it checks if val1 is equal to val2
+# val1 -ne val2 means it checks if val1 is not equal to val2
+# val1 -gt val2 means it checks if val1 is greater than val2
+# val1 -ge val2 means it checks if val1 is greater than or equal to val2
+# val1 -lt val2 means it checks if val1 is lesser than val2
+# val1 -le val2 means it checks if val1 is less than or equal to val2
+
+# NUM1=31
+# NUM2=5
+
+# if [ "$NUM1" -eq "$NUM2" ]
+# then 
+#     echo both numbers are equal
+# else
+#     echo both numbers are not equal
+# fi
+
+# if [ "$NUM1" -gt "$NUM2" ]
+# then    
+#     echo $NUM1 is greater than $NUM2
+# else
+#     echo $NUM1 is less than $NUM2
+# fi
+
+# File conditions
+# -d <file> True if the given string <file> is a directory
+# -f <file> True if the given string <file> is a file
+# -e <file> True if the given file exists or not but this is not portable and -f is heavily used instead
+# -g <file> True if group id is set on the given file
+# -u <file> True if user id is set on the given file
+# -r <file> True if the given file is readable
+# -w <file> True if the given file is writable
+# -x <file> True if the given file is executable
+# -s <file> True if the file has non zero size
+
+# FILE="test.txt"
+# if [ -w "$FILE" ]
+# then 
+#     echo The given directory is writeable
+# else
+#     echo The given directory is NOT writable
+# fi
+
+# Case statements
+# each condition statement ends with ')'
+# instead of break we make use of ';;'
+# to make use of default make use of '*)' => break down into '*' and ')', latter is used to end the case statement
+
+# read -p "Are you 21 or older: " ANSWER
+# case "$ANSWER" in
+#     [yY] | [yY][eE][sS])
+#         echo "You may have a drink"
+#         ;;
+#     [nN] | [nN][oO])
+#         echo "You cannot have a drink"
+#         ;;
+#     *)
+#         echo "Please reply with a y/yes or n/no"
+#        ;;
+# esac
+
+# Loops
+# Simple For loop
+# NAMES="Aakarsh Achintya Manik Tushar"
+# for NAME in $NAMES
+#     do
+#         echo $NAME
+# done
+
+# Using for loops to rename files
+# FILES=$(ls *.txt)
+# for FILE in $FILES
+#     do
+#         mv $FILE "NEW"-$FILE
+# done
+
+# LINE=1
+# while read -r CURRENT_LINE
+#     do
+#         echo $LINE: $CURRENT_LINE
+#         ((LINE++))
+# done < "1.txt"
+
+# Functions
+# functions with no parameters
+# function helloworld() {
+#     echo "Hello World"
+# }
+
+# helloworld
+
+# #Functions with parameters
+# function greeting() {
+#     echo Hello $1 and you are assigned age $2
+# }
+
+# greeting "Aakarsh" 23