====== BASH Scripting Reference ======

==== Links/Resources ====
[[https://linuxhint.com/3hr_bash_tutorial/|3 Hour Bash Tutorial]] \\

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==== Functions ====
<code>
function double()
{
   Result = $1 * 2
}
Double 12
</code>

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==== If / Elif / Else ====
[[https://linuxhint.com/bash_if_else_examples/|link]]
<code>

if CONDITION-TO-TEST; then
     CODE-TO-EXECUTE-1
elif NEXT-CONDITION-TO-TEST; then
     CODE-TO-EXECUTE-2
elif NEXT-CONDITION-TO-TEST; then
     CODE-TO-EXECUTE-2
else
     CODE-TO-EXECUTE-2
fi
</code>

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==== Ask a yes/no question (case insensitive comparison)====
<code>
read -p "Do it? [y/n] " yesno
if [[ "${yesno,,}" != "y" ]]; then
   echo "OK. Exiting..."
   exit 1  # Exit with an error code to indicate user cancelled
else
   # Rest of your script if user confirms (y/Y)
   echo "OK. Continuing..."
fi 
</code>

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==== Check if running as root/sudo ====
<code>
if [[ $(/usr/bin/id -u) -ne 0 ]]; then
    echo "Not running as root"
    exit
fi
</code>

<code>
touch /etc/test.file
if [ $? -ne 0 ]; then
  echo "This command needs to be run with sudo!"
  exit 1
fi
</code>
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==== Pass Command Line Parameters ====
<code>
#!/bin/bash
echo "1st parameter = $1 "
echo "2nd Parameter = $2 "
</code>

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==== Test if variable is empty ====
<code>
if [ -z "$var" ]
then
  echo "\$var is empty"
else
  echo "\$var is NOT empty"
fi
</code>

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==== Add a user, specifying group membership ====
<code>
sudo useradd -m -g users -G sudo,docker username
sudo id username
</code>
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