SSH automation in Bash Scripting - Step-by-Step Execution

Concept Flow - SSH automation

Start script

↓

Check SSH key

Yes↓

Run ssh command

↓

Receive output

↓

Process output or error

↓

End script

The script checks for SSH keys, runs a remote command via SSH, receives output, and ends.

Execution Sample

Bash Scripting

ssh user@host 'echo Hello from remote'
echo Done

Connects to remote host via SSH and runs a simple echo command, then prints Done locally.

Execution Table

Step	Action	Command/Condition	Result	Output
1	Start script	N/A	Script begins
2	Check SSH key	ssh-keygen -F host	Key found or not	Entry printed if key exists
3	Run ssh command	ssh user@host 'echo Hello from remote'	Connected and command executed	Hello from remote
4	Print local message	echo Done	Printed locally	Done
5	End script	N/A	Script ends

💡 Script ends after running remote command and printing local message.

Variable Tracker

Variable	Start	After SSH command	Final
ssh_output		Hello from remote	Hello from remote
local_message			Done

Key Moments - 2 Insights

Why does the script not ask for a password every time?

Because SSH keys are set up and found in step 2 (see execution_table row 2), allowing passwordless login.

What happens if the remote command fails?

The ssh command returns an error and no output is captured in ssh_output (see execution_table row 3). The script still prints Done locally.

Visual Quiz - 3 Questions

Look at the execution table, what is the output of the ssh command at step 3?

A Done

B Hello from remote

C No output

D Error message

💡 Hint

Check the Output column in execution_table row 3.

At which step does the script print the local message 'Done'?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at the Action and Output columns in execution_table row 4.

If SSH keys are not set up, what would change in the execution flow?

A The script would ask for a password at step 3

B The script would skip the ssh command

C The script would print 'Done' before ssh command

D The script would end immediately

💡 Hint

Think about what happens when ssh-keygen -F host does not find a key (execution_table row 2).

Concept Snapshot

SSH automation runs commands on remote machines without manual login.
Use SSH keys for passwordless access.
Basic command: ssh user@host 'command'.
Capture output to variables for processing.
Automate repetitive remote tasks easily.

Full Transcript

This visual execution shows how SSH automation works in a bash script. The script starts and checks if SSH keys exist for passwordless login. Then it runs a remote command using ssh, capturing the output 'Hello from remote'. After that, it prints a local message 'Done'. The script ends after these steps. Key points include the importance of SSH keys to avoid password prompts and how output is handled. The execution table tracks each step, the commands run, and their results. Variables like ssh_output store remote command output. This helps beginners see how SSH automation scripts flow and behave.