Plantuml Ascii

PlantUML ASCII art diagram generator

Generate terminal-friendly ASCII or Unicode text diagrams from PlantUML source, choosing -txt for pure ASCII and -utxt for box-drawing output that reads well in fixed-width environments.

When to invoke

• "Create an ASCII diagram."
• "Convert this PlantUML diagram to text output."
• "Generate a terminal-friendly sequence diagram."
• "Use plantuml -utxt for a README diagram."
• "Make a text-based class, activity, state, component, use case, or deployment diagram."

ASCII diagram purpose

Create text-based ASCII art diagrams using PlantUML. Perfect for documentation in terminal environments, README files, emails, or any scenario where graphical diagrams aren't suitable.

What is PlantUML ASCII art?

PlantUML can generate diagrams as plain text (ASCII art) instead of images. This is useful for:

• Terminal-based workflows
• Git commits/PRs without image support
• Documentation that needs to be version-controlled
• Environments where graphical tools aren't available

Prerequisites and context

 # macOS
brew install plantuml

 # Linux (varies by distro)
sudo apt-get install plantuml  # Ubuntu/Debian
sudo yum install plantuml      # RHEL/CentOS

 # Or download JAR directly
wget https://github.com/plantuml/plantuml/releases/download/v1.2024.0/plantuml-1.2024.0.jar

Output Formats

Procedure

1. Create a PlantUML diagram file, for example:

@startuml
participant Bob
actor Alice

Bob -> Alice : hello
Alice -> Bob : Is it ok?
@enduml

2. Generate ASCII art:

 # Standard ASCII output
plantuml -txt diagram.puml

 # Unicode-enhanced output (better looking)
plantuml -utxt diagram.puml

 # Using JAR directly
java -jar plantuml.jar -txt diagram.puml
java -jar plantuml.jar -utxt diagram.puml

3. View output:

Output is saved as diagram.atxt (ASCII) or diagram.utxt (Unicode).

Diagram Types Supported

Sequence Diagram

@startuml
actor User
participant "Web App" as App
database "Database" as DB

User -> App : Login Request
App -> DB : Validate Credentials
DB --> App : User Data
App --> User : Auth Token
@enduml

Class Diagram

@startuml
class User {
  +id: int
  +name: string
  +email: string
  +login(): bool
}

class Order {
  +id: int
  +total: float
  +items: List
  +calculateTotal(): float
}

User "1" -- "*" Order : places
@enduml

Activity Diagram

@startuml
start
:Initialize;
if (Is Valid?) then (yes)
  :Process Data;
  :Save Result;
else (no)
  :Log Error;
  stop
endif
:Complete;
stop
@enduml

State Diagram

@startuml
[*] --> Idle
Idle --> Processing : start
Processing --> Success : complete
Processing --> Error : fail
Success --> [*]
Error --> Idle : retry
@enduml

Component Diagram

@startuml
[Client] as client
[API Gateway] as gateway
[Service A] as svcA
[Service B] as svcB
[Database] as db

client --> gateway
gateway --> svcA
gateway --> svcB
svcA --> db
svcB --> db
@enduml

Use Case Diagram

@startuml
actor "User" as user
actor "Admin" as admin

rectangle "System" {
  user -- (Login)
  user -- (View Profile)
  user -- (Update Settings)
  admin -- (Manage Users)
  admin -- (Configure System)
}
@enduml

Deployment Diagram

@startuml
actor "User" as user
node "Load Balancer" as lb
node "Web Server 1" as ws1
node "Web Server 2" as ws2
database "Primary DB" as db1
database "Replica DB" as db2

user --> lb
lb --> ws1
lb --> ws2
ws1 --> db1
ws2 --> db1
db1 --> db2 : replicate
@enduml

Command-Line Options

 # Specify output directory
plantuml -txt -o ./output diagram.puml

 # Process all files in directory
plantuml -txt ./diagrams/

 # Include dot files (hidden files)
plantuml -txt -includeDot diagrams/

 # Verbose output
plantuml -txt -v diagram.puml

 # Specify charset
plantuml -txt -charset UTF-8 diagram.puml

Ant Task Integration

<target name="generate-ascii">
  <plantuml dir="./src" format="txt" />
</target>

<target name="generate-unicode-ascii">
  <plantuml dir="./src" format="utxt" />
</target>

Gotchas

1. Keep it simple: Complex diagrams don't render well in ASCII
2. Short labels: Long text breaks ASCII alignment
3. Use Unicode (-utxt): Better visual quality with box-drawing chars
4. Test before sharing: Verify in terminal with fixed-width font
5. Consider alternatives: For complex diagrams, use Mermaid.js or graphviz

Example Output Comparison

Standard ASCII (-txt):

     ,---.          ,---.
     |Bob|          |Alice|
     `---'          `---'
      |   hello      |
      |------------->|
      |              |
      |  Is it ok?   |
      |<-------------|
      |              |

Unicode ASCII (-utxt):

┌─────┐        ┌─────┐
│ Bob │        │Alice│
└─────┘        └─────┘
  │   hello      │
  │─────────────>│
  │              │
  │  Is it ok?   │
  │<─────────────│
  │              │

Quick reference

 # Create sequence diagram in ASCII
cat > seq.puml << 'EOF'
@startuml
Alice -> Bob: Request
Bob --> Alice: Response
@enduml
EOF

plantuml -txt seq.puml
cat seq.atxt

 # Create with Unicode
plantuml -utxt seq.puml
cat seq.utxt

Troubleshooting

Problem: Garbled Unicode characters

• Solution: Ensure terminal supports UTF-8 and has proper font

Problem: Diagram looks misaligned

• Solution: Use fixed-width font (Courier, Monaco, Consolas)

Problem: Command not found

• Solution: Install PlantUML or use Java JAR directly

Problem: Output file not created

• Solution: Check file permissions, ensure PlantUML has write access

Output template

## PlantUML ASCII result

**Status:** generated | blocked
**Source:** `<diagram.puml>`
**Format:** `-txt` | `-utxt`
**Output:** `<diagram.atxt | diagram.utxt>`

### Command
`plantuml -txt diagram.puml`

### Preview
```text
<paste the generated ASCII or Unicode diagram>

Validation

• PlantUML command completed: pass | fail
• Output file exists: pass | fail
• Fixed-width rendering checked: pass | fail

## Quality gate

- [ ] The source file is valid PlantUML bounded by `@startuml` and `@enduml`.
- [ ] The chosen output flag matches the request: `-txt` for pure ASCII, `-utxt` for Unicode box-drawing characters.
- [ ] The output path is reported as `.atxt` for ASCII or `.utxt` for Unicode.
- [ ] Labels are short enough to preserve alignment in a fixed-width font.
- [ ] Complex diagrams are simplified or the user is told when Mermaid.js or graphviz is a better fit.
- [ ] Installation blockers name the missing command and offer `brew install plantuml`, `sudo apt-get install plantuml`, `sudo yum install plantuml`, or `java -jar plantuml.jar`.

## References

- [PlantUML release JAR example](https://github.com/plantuml/plantuml/releases/download/v1.2024.0/plantuml-1.2024.0.jar)