Bash 101

bash_101.sh

#!/bin/bash

echo "[1. echo]"
echo "Hello World"

GREETING="Hello World"
echo "[2. variable]"
echo "${GREETING}"

echo "[3. function]" 
function say_hello()
{
  echo "${GREETING}" 
}
say_hello

echo "[4. function with parameters]"
function say() 
{
  echo "${1}"  
}
say "${GREETING}"

GREETING_ARRAY=(
  "Hello"  
  "World"
)
echo "[5. arrays]"
for WORD in "${GREETING_ARRAY[@]}"
do
  echo "${WORD}"
done

echo "[6. associative arrays]"
declare -a MESSAGE_HASH
MESSAGE_HASH[greeting]="${GREETING}"
echo "${MESSAGE_HASH[greeting]}"

echo "[7. while]"
COUNTER=0
while [ $COUNTER -le 1 ]
do
  echo "${GREETING_ARRAY[${COUNTER}]}"
  ((COUNTER++))
done

echo "[8. if/else]"
if [ 0 -eq 1 ]; then
  echo "If..."
elif [ "a" == "a" ]; then
  echo "${GREETING}"
else 
  echo "Else..."
fi

echo "[9. executing a utility]"
FILE_MESSAGE=$(cat hello_world.txt)
echo "${FILE_MESSAGE}"

echo "[10. using an external file]"
source external_file.sh
external_greeting

exit 0