fix: chapter 7 samples, fixes #356 (#360)

samples/templates/advanced.template.sh

@@ -0,0 +1,17 @@
+file_path="$HOME/effective-shell/templates/advanced.template.sh"
+env_var_names=$(env | sed -E -n 's/^([^=]+)(=.*)/\1/p')
+
+for env_var_name in ${env_var_names}; do
+    echo "Checking for '${env_var_name}'..."
+
+    if grep -q "%${env_var_name}%" "${file_path}"; then
+        echo "-> Found '${env_var_name}', expanding now..."
+
+        env_var_value="${!env_var_name}"
+        escaped_value=$(echo ${env_var_value} | sed -e 's/[\/&]/\\&/g')
+
+        sed -e "s/%${env_var_name}%/${escaped_value}/" \
+            "${file_path}" > "${file_path}.tmp"
+        mv "${file_path}.tmp" "${file_path}"
+    fi
+done

samples/templates/credentials.sh

@@ -0,0 +1,2 @@
+USERNAME=admin
+PASSWORD=ThisIsVerySensitive!

samples/templates/credentials.template.sh

@@ -0,0 +1,2 @@
+USERNAME=admin
+PASSWORD=%PASSWORD%