Htykuut

I use graphviz to draw a diagram.

The placement of the nodes are not ideal. I would like the six nodes to be roughly placed in a 2 by 3 table:

file_in   stdin_in     string_in



file_out  stdout_out   variable_out

I have tried to add weights to some edges but still fails to move the nodes into such a table. See my dot program below. Thanks.

digraph G {



/* directly betw inputs */

node [color=black]

string_in -> stdin_in [label="redirection"];

 file_in -> stdin_in [label="redirection"];

 stdin_in -> file_in [label="device file /dev/stdin, or arg -", weight=8];

 stdin_in -> string_in [label="xargs"]; 



/* directly betw outputs */

node [color=red]

edge [color=red]

  stdout_out -> file_out [label="redirection" fontcolor="red"];

  file_out -> stdout_out [label="/dev/stdout or arg -" fontcolor="red"];



/* directly from input to output */

edge [color=blue]

 stdin_in -> stdout_out [label="cat or tee" fontcolor="blue" weight=8];

 stdin_in -> file_out [label = "tee > /dev/null" fontcolor = "blue"]; 

 string_in -> stdout_out [label="echo -n" fontcolor="blue" weight=2];

 file_in -> stdout_out [label="cat" fontcolor="blue"];

 file_in -> file_out [label="none" fontcolor="blue"];

 string_in -> variable_out [label="assignment" fontcolor="blue"];



/* directly from output to input */

edge [color=green]

 stdout_out -> stdin_in [label="pipe" fontcolor="green"];

 stdout_out -> file_in  [label="process substitution"  fontcolor="green"];

 stdout_out -> string_in [label="command substitution"  fontcolor="green"];

 file_out -> file_in [label="none"  fontcolor="green"];

 variable_out -> string_in [label="parameter expansion"  fontcolor="green"];

}

The key point here is using rank = same; I have added this instruction at the top of your code. I have also increased the distance between the two rank levels so that there is more space for the edge labels. I have also changed the weights you had given to the edges in order to have a matrix like appearance.

Two more things I would recommend:

• rather than the HTML-like syntax for the node, use the standard graphviz format; matter of taste, but I find it easier to read and it is more flexible, see (How shall escape `>` in an edge label?),


• when creating edges from nodes lower in the hierarchy to higher ones, don't use b->a, rather write a->b[dir="back"]; this avoids graphviz getting confused when the number of nodes increases

I have not completely edited the file, as it is not strictly necessary for the two items just mentioned - here the job I have done:

digraph G {



# layout

ranksep = 2

{ rank = same; file_in stdin_in string_in }

{ rank = same; file_out stdout_out variable_out }



/* directly betw inputs */

node [color=black]

 string_in -> stdin_in [label="redirection"];

 file_in -> stdin_in [label="redirection"];

 stdin_in -> file_in [label="device file /dev/stdin, or arg -"] 

 stdin_in -> string_in [label="xargs"]; 



/* directly betw outputs */

node [color=red]

edge [color=red]

  stdout_out -> file_out [label=<<font color="red">redirection</font>>];

  file_out -> stdout_out [label=<<font color="red">/dev/stdout or arg -</font>>];



/* directly from input to output */

edge [color=blue]

 stdin_in -> stdout_out [label=<<font color="blue">cat or tee</font>> weight = 10];

 # stdin_in -> file_out [label=<<font color="blue">tee /dev/null</font>>]; 

 stdin_in -> file_out[ label = "tee > /dev/null" fontcolor = "blue" ];

 string_in -> stdout_out [label=<<font color="blue">echo -n</font>> ];

 file_in -> stdout_out [label=<<font color="blue">cat</font>> ];

 file_in -> file_out [label = "none" fontcolor = "blue" weight = 10];

 string_in -> variable_out [label = "assignment" fontcolor = "blue" weight = 10 ];



/* directly from output to input */

edge [color=green]

 stdout_out -> stdin_in [label=<<font color="green">pipe</font>>];

 stdout_out -> file_in  [label=<<font color="green">process substitution</font>>];

 stdout_out -> string_in [label=<<font color="green">command substitution</font>>];

 file_in -> file_out [label="none" fontcolor="green" dir = back ];

 variable_out -> string_in [label=<<font color="green">parameter expansion</font>>];

}

which gives you