I'm trying to render the output of a linux shell command in HTML. For example, systemctl status mysql looks like this in my terminal:
As I understand from Floz'z Misc I was expecting that the underlying character stream would contain control codes. But looking at it in say hexyl (systemctl status mysql | hexyl) I can't see any codes:
Looking near the bottom on lines 080 and 090 where the text "Active: failed" is displayed, I was hoping to find some control sequences to change the color to red. While not necessarily ascii, I used some ascii tables to help me:
- looking at the second lot of 8 characters on line 090 where the letters
ive: faare displayed, I find: - 69 = i
- 76 = v
- 65 = e
- 3a = :
- 20 = space
- 66 = f
- 61 = a
- 69 = i
There are no bytes for control sequences.
I wondered if hexyl is choosing not to display them so I wrote a Java program which outputs the raw bytes after executing the process as a bash script and the results are the same - no control sequences.
The Java is roughly:
p = Runtime.getRuntime().exec(new String[]{"/bin/sh", "-c", "systemctl status mysql"}); // runs in the shell
p.waitFor();
byte[] bytes = p.getInputStream().readAllBytes();
for(byte b : bytes) {
System.out.println(b + "\t" + ((char)b));
}
That outputs:
...
32
32
32
32
32
65 A
99 c
116 t
105 i
118 v
101 e
58 :
32
102 f
97 a
105 i
108 l
101 e
100 d
...
So the question is: How does bash know that it has to display the word "failed" red?
