Execute Remote Commands via SSH in Bash

#!/bin/bash

REMOTE_USER="webadmin"
REMOTE_HOST="your_server.com" # Replace with your actual server hostname or IP
REMOTE_WEB_ROOT="/var/www/html/myapp"

# --- Method 1: Execute a single command and check its exit status ---
echo "
--- Checking remote directory listing ---"
ssh "$REMOTE_USER@$REMOTE_HOST" "ls -la $REMOTE_WEB_ROOT"

if [ $? -eq 0 ]; then
  echo "Remote 'ls' command executed successfully."
else
  echo "Error: Remote 'ls' command failed. Check SSH connection/permissions."
fi

# --- Method 2: Execute multiple commands as a single string ---
echo "
--- Creating a remote test file and listing it ---"
ssh "$REMOTE_USER@$REMOTE_HOST" "cd $REMOTE_WEB_ROOT && echo 'Hello from remote script' > remote_test_file.txt && ls remote_test_file.txt"

# --- Method 3: Execute a local script block remotely using a here-document ---
echo "
--- Running a more complex remote task (e.g., checking service status) ---"
ssh "$REMOTE_USER@$REMOTE_HOST" << 'EOF'
  echo "Executing complex block on $(hostname)"
  cd "$REMOTE_WEB_ROOT" || { echo "Error: Cannot change directory to $REMOTE_WEB_ROOT"; exit 1; }
  DATE_STR=$(date +%Y%m%d_%H%M%S)
  echo "Timestamp: $DATE_STR" >> remote_log.txt
  echo "Checking web server status..."
  systemctl is-active --quiet apache2 && echo "Apache is running." || echo "Apache is NOT running."
  # Clean up the test file created earlier
  rm -f remote_test_file.txt
  echo "Remote cleanup complete."
EOF

# --- Method 4: Piping a local script into SSH ---
echo "
--- Running a local script on remote (piped) ---"
echo '#!/bin/bash
REMOTE_SCRIPT_VAR="Piped Variable"
echo "Remote script executed. Value: $REMOTE_SCRIPT_VAR"
' | ssh "$REMOTE_USER@$REMOTE_HOST" 'bash -s'

echo "
All remote operations attempted."

# Remember to set up SSH keys for passwordless authentication for automation.