Capture Real Command Output with Exec

In this tutorial, you'll record a real git workflow showing actual command output. Unlike the typing demo tutorial where we simulated typing, here you'll execute actual commands and capture their real output.

Your finished recording will show:

  1. Checking git status
  2. Creating a new file
  3. Staging and committing the changes
  4. Viewing the commit log

This is perfect for creating accurate documentation, demos, and tutorials showing real tool behavior. This tutorial takes about 20 minutes.

Prerequisites

You should complete the Typing Demo tutorial first to understand basic VCR# concepts.

You'll also need:

  • Git installed and configured
  • A test repository (we'll create one)
  • About 20 minutes

Step 1: Create a Test Repository

First, let's create a test git repository to work with:

mkdir vcr-git-demo
cd vcr-git-demo
git init
git config user.name "Demo User"
git config user.email "demo@example.com"

Create a tape file called git-workflow.tape:

Output git-workflow.gif
  
Set Cols 100
Set Rows 30
Set Theme Dracula
Set Shell "bash"

We're ready to record real commands.

Step 2: Execute Your First Real Command

Add this line to git-workflow.tape:

Exec "git status"
Sleep 1s

Run the recording:

vcr git-workflow.tape

Open the GIF. Notice something different from the typing demo: the output appeared instantly, and it shows the actual git status output from your repository.

The Exec command runs the actual program and captures its real output. VCR# waits for the command to finish before continuing to the next line.

Step 3: Chain Multiple Commands

Update your tape file to create and commit a file:

Output git-workflow.gif
  
Set Cols 100
Set Rows 30
Set Theme Dracula
Set Shell "bash"
  
Exec "git status"
Sleep 500ms
  
Exec "echo 'Hello from VCR#' > README.md"
Sleep 500ms
  
Exec "git add README.md"
Sleep 500ms
  
Exec "git commit -m 'Add README'"
Sleep 500ms
  
Exec "git log --oneline -n 1"
Sleep 2s

Run the recording again:

vcr git-workflow.tape

Watch the GIF. You'll see each command execute in sequence with their real output: the file is created, staged, committed, and the commit appears in the log. Each Sleep command creates a pause so viewers can read the output.

Notice how VCR# waits for each command to complete before moving to the next one. You don't have to guess how long commands will take.

Step 4: Wait for Specific Output

Sometimes you want to wait for specific text to appear before continuing. Let's add a Wait command:

Output git-workflow.gif
  
Set Cols 100
Set Rows 30
Set Theme Dracula
Set Shell "bash"
  
Exec "git status"
Sleep 500ms
  
Exec "echo 'Hello from VCR#' > README.md"
Sleep 500ms
  
Exec "git add README.md"
Sleep 500ms
  
Exec "git commit -m 'Add README'"
Wait "Add README"
Sleep 500ms
  
Exec "git log --oneline -n 1"
Sleep 2s

Notice the Wait "Add README" line. This tells VCR# to pause until it sees "Add README" in the terminal output before continuing. This is more reliable than using fixed delays when output timing varies.

Run the recording:

vcr git-workflow.tape

The recording works the same, but now it explicitly waits for the commit message to appear. This technique is useful when commands produce output gradually or when timing is unpredictable.

Next Steps

Great work! You've learned to:

  • Execute real commands with Exec
  • Chain multiple commands in sequence
  • Wait for specific output with Wait
  • Create accurate recordings of real workflows

You now know both simulated typing (from the typing demo) and real execution.

Complete Code

Here's the full git-workflow.tape file:

Output git-workflow.gif
  
Set Cols 100
Set Rows 30
Set Theme Dracula
Set Shell "bash"
  
Exec "git status"
Sleep 500ms
  
Exec "echo 'Hello from VCR#' > README.md"
Sleep 500ms
  
Exec "git add README.md"
Sleep 500ms
  
Exec "git commit -m 'Add README'"
Wait "Add README"
Sleep 500ms
  
Exec "git log --oneline -n 1"
Sleep 2s
Previous
Next