Mermaid ASCII

Render mermaid diagrams in your terminal:

Installation

You can download the binary from Github releases:

# Get the latest release
$ curl -s https://api.github.com/repos/AlexanderGrooff/mermaid-ascii/releases/latest | grep "browser_download_url.*mermaid-ascii" | grep "$(uname)_$(uname -m)" | cut -d: -f2,3 | tr -d \" | wget -qi -
# Unzip it
$ tar xvzf mermaid-ascii_*.tar.gz
$ ./mermaid-ascii --help

You can also build it yourself:

$ git clone
$ cd mermaid-ascii
$ go build
$ mermaid-ascii --help

Or using Nix:

$ git clone
$ cd mermaid-ascii
$ nix build
$ ./result/bin/mermaid-ascii --help

Usage

You can render graphs directly from the command line or start a web interface to render them interactively.

$ cat test.mermaid
graph LR
A --> B & C
B --> C & D
D --> C
$ mermaid-ascii --file test.mermaid
+---+     +---+     +---+
|   |     |   |     |   |
| A |---->| B |---->| D |
|   |     |   |     |   |
+---+     +---+     +---+
  |         |         |
  |         |         |
  |         |         |
  |         |         |
  |         v         |
  |       +---+       |
  |       |   |       |
  ------->| C |<-------
          |   |
          +---+

# Increase horizontal spacing
$ mermaid-ascii --file test.mermaid -x 8
+---+        +---+        +---+
|   |        |   |        |   |
| A |------->| B |------->| D |
|   |        |   |        |   |
+---+        +---+        +---+
  |            |            |
  |            |            |
  |            |            |
  |            |            |
  |            v            |
  |          +---+          |
  |          |   |          |
  ---------->| C |<----------
             |   |
             +---+

# Increase box padding
$ mermaid-ascii -f ./test.mermaid -p 3
+-------+     +-------+     +-------+
|       |     |       |     |       |
|       |     |       |     |       |
|       |     |       |     |       |
|   A   |---->|   B   |---->|   D   |
|       |     |       |     |       |
|       |     |       |     |       |
|       |     |       |     |       |
+-------+     +-------+     +-------+
    |             |             |
    |             |             |
    |             |             |
    |             |             |
    |             v             |
    |         +-------+         |
    |         |       |         |
    |         |       |         |
    |         |       |         |
    --------->|   C   |<---------
              |       |
              |       |
              |       |
              +-------+

# Labeled edges
$ cat test.mermaid
graph LR
A --> B
A --> C
B --> C
B -->|example| D
D --> C
$ mermaid-ascii -f ./test.mermaid
+---+     +---+         +---+
|   |     |   |         |   |
| A |---->| B |-example>| D |
|   |     |   |         |   |
+---+     +---+         +---+
  |         |             |
  |         |             |
  |         |             |
  |         |             |
  |         v             |
  |       +---+           |
  |       |   |           |
  ------->| C |<-----------
          |   |
          +---+

# Top-down layout
$ cat test.mermaid
graph TD
A --> B
A --> C
B --> C
B -->|example| D
D --> C
$ mermaid-ascii -f ./test.mermaid
+---------+          
|         |          
|    A    |-------|  
|         |       |  
+---------+       |  
     |            |  
     |            |  
     |            |  
     |            |  
     v            v  
+---------+     +---+
|         |     |   |
|    B    |---->| C |
|         |     |   |
+---------+     +---+
     |            ^  
     |            |  
  example         |  
     |            |  
     v            |  
+---------+       |  
|         |       |  
|    D    |-------|  
|         |          
+---------+          

$ mermaid-ascii --help
Generate ASCII diagrams from mermaid code.

Usage:
  mermaid-ascii [flags]
  mermaid-ascii [command]

Available Commands:
  completion  Generate the autocompletion script for the specified shell
  help        Help about any command
  web         HTTP server for rendering mermaid diagrams.

Flags:
  -p, --borderPadding int   Padding between text and border (default 1)
  -c, --coords              Show coordinates
  -f, --file string         Mermaid file to parse
  -h, --help                help for mermaid-ascii
  -x, --paddingX int        Horizontal space between nodes (default 5)
  -y, --paddingY int        Vertical space between nodes (default 5)
  -v, --verbose             Verbose output

Use "mermaid-ascii [command] --help" for more information about a command.

# And some ridiculous example
$ mermaid-ascii -f complex.mermaid
+---+     +---+     +---+     +---+     +---+     +---+     +---+     +---+     +---+
|   |     |   |     |   |     |   |     |   |     |   |     |   |     |   |     |   |
| A |---->| B |---->| D |---->| E |---->| I |---->| M |---->| Q |---->| U |---->| Y |
|   |     |   |  |  |   |     |   |  |  |   |  |  |   |  |  |   |  |  |   |  |  |   |
+---+     +---+  |  +---+     +---+  |  +---+  |  +---+  |  +---+  |  +---+  |  +---+
  |         |    |    |         |    |    |    |    |    |    |    |    |    |       
  |         |    |    |         |    |    |    |    |    |    |    |    |    |       
  |         -----|    -----|---------|---------|---------|---------|---------|       
  |         |    |         |    |    |    |    |    |    |    |    |    |            
  |         |    |         |    |    |    |    |    |    |    |    |    |            
  |       +---+  |  +---+  |  +---+  |  +---+  |  +---+  |  +---+  |  +---+          
  |       |   |  |  |   |  |  |   |  |  |   |  |  |   |  |  |   |  |  |   |          
  ------->| C |  -->| F |<--->| H |---->| L |---->| P |---->| T |---->| X |          
          |   |     |   |  |  |   |  |  |   |  |  |   |  |  |   |  |  |   |          
          +---+     +---+  |  +---+  |  +---+  |  +---+  |  +---+  |  +---+          
            |         |    |         |         |         |         |                 
            |         |    |         |         |         |         |                 
            |         -----|         |         |         |         |                 
            |         |    |         |         |         |         |                 
            |         |    |         |         |         |         |                 
            |       +---+  |  +---+  |  +---+  |  +---+  |  +---+  |                 
            |       |   |  |  |   |  |  |   |  |  |   |  |  |   |  |                 
            ------->| G |  -->| J |--|->| N |--|->| R |--|->| V |<-|                 
                    |   |     |   |  |  |   |  |  |   |  |  |   |  |                 
                    +---+     +---+  |  +---+  |  +---+  |  +---+  |                 
                      |         |    |    |    |    |    |    |    |                 
                      |         |    |    |    |    |    |    |    |                 
                      |         -----|    -----|    -----|    -----|                 
                      |         |         |         |         |                      
                      |         |         |         |         |                      
                      |       +---+     +---+     +---+     +---+                    
                      |       |   |     |   |     |   |     |   |                    
                      ------->| K |---->| O |---->| S |---->| W |                    
                              |   |     |   |     |   |     |   |                    
                              +---+     +---+     +---+     +---+                    

Colored output is also supported (given that your terminal supports it) using the classDef syntax:

graph LR
classDef example1 color:#ff0000
classDef example2 color:#00ff00
classDef example3 color:#0000ff
test1:::example1 --> test2
test2:::example2 --> test3:::example3

This results in the following graph:

How it works

We parse a mermaid file into basic components in order to render a grid. The grid is used for mapping purposes, which is eventually converted to a drawing. The grid looks a bit like this:

There are three grid-points per node, and one in-between nodes.
These coords don't have to be the same size, as long as they
can be used for pathing purposes where we convert them to drawing
coordinates.
This allows us to navigate edges between nodes, like the arrow in this
drawing taking the path [(2,1), (3,1), (3,5), (4,5)].
    0      1      2  3  4      5      6
    |      |      |  |  |      |      |
    v      v      v  v  v      v      v
                                       
0-> +-------------+     +-------------+
    |             |     |             |
1-> |  Some text  |---  |  Some text  |
    |             |  |  |             |
2-> +-------------+  |  +-------------+
                     |                 
3->                  |                 
                     |                 
4-> +-------------+  |  +-------------+
    |             |  |  |             |
5-> |  Some text  |  -->|  Some text  |
    |             |     |             |
6-> +-------------+     +-------------+

You can show these coords in your graph by enabling the --coords flag:

$ mermaid-ascii -f ./test.mermaid --coords
   01  23    45  67  89       0
   0123456789012345678901234567
0 0+---+     +---+   +--------+
  1|   |     |   |   |        |
1 2| A |-123>| B |-->|   D    |
  3|   |     |   |   |        |
2 4+---+     +---+   +--------+
  5  |         |          |
3 6  |         2          |
  7  |         v       123456
4 8  |       +---+        |
  9  |       |   |        |
510  ------->| C |<--------
 11          |   |
612          +---+

Note that with --coords enabled, the grid-coords shown show the starting location of the coord, not the center of the coord. This is why (1,0) is next to (0,0) instead of in the center of the A node.

TODOs

The baseline components for Mermaid work, but there are a lot of things that are not supported yet. Here's a list of things that are not yet supported:

Syntax support

• Labelled edges (like A -->|label| B)
• Graph directions like graph LR and graph TB
• classDef and class
• A & B
• Multiple arrows on one line (like A --> B --> C)
• subgraph
• Shapes other than rectangles
• Whitespacing and comments

Rendering

• Prevent arrows overlapping nodes
• Diagonal arrows
• Place nodes in a more compact way
• Prevent rendering more than X characters wide (like default 80 for terminal width)