How does apt render its fancy progress bar?

Re:How does apt render its fancy progress bar? by rbonvall on Wednesday October 13, 2021 @10:51AM (#28852883)

Standardness notwithstanding, using tput is more readable and memorable. I can type this from memory:

    echo "I'm $(tput setaf 4)blue$(tput sgr0)."

but I couldn't get this one right without looking it up:

    echo -e "I'm \033[0;34mblue\033[0m."

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Re:How does apt render its fancy progress bar? by junon on Wednesday October 13, 2021 @12:50PM (#28854505)

Because you're using a lot more characters than you need.

    echo -e "I'm \e[34mblue\e[m."

However, `tput` is definitely the more 'correct' approach. What actual benefit it affords you over the hardcoded escapes is left to edge-cases and very, very old or otherwise niche terminal emulators.

By the way, the `3x` means foreground, the `4x` means background. `x` is a number between 0 and 7 (inclusive) that indicates the color. `x=8` means "extended"/non-standard and generally takes a few more control codes afterward, and `x=9` means "reset".

If you know binary, you can remember the 0-7 colors. It's a 3-bit code corresponding to BGR (where B is the MSB).

    BGR
    000 = 0 = black
    001 = 1 = red
    010 = 2 = green
    011 = 3 = yellow
    100 = 4 = blue
    101 = 5 = magenta
    110 = 6 = cyan
    111 = 7 = white

You can also add 60 to the code to make it "bright", e.g. red foreground (31) can be made bright red by adding 31+60=91. Same can be applied to backgrounds (4x+60=10x).

The bright codes are less supported though admittedly I've never seen a modern emulator that doesn't. It also gives you bright colors on old Windows cmd.exe prompts without needing the bold mode (1).

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Re:How does apt render its fancy progress bar? by faho on Wednesday October 13, 2021 @11:46AM (#28853683)

Still not particularly readable or memorable. You still need to remember that blue is color number 4 and that "sgr0" is "exit_attribute_mode", what you might call "reset".

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Re:How does apt render its fancy progress bar? by tomc1985 on Wednesday October 13, 2021 @12:26PM (#28854217)

Store the sequences in variables and put those instead. You get readability and locality!

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Re:How does apt render its fancy progress bar? by nick__m on Wednesday October 13, 2021 @12:51PM (#28854519)

I was about to post the exact same reply so I will post it as an example:

  #!/bin/sh
  BLUE=$(tput setaf 4)
  RST=$(tput sgr0)
  echo "I'm ${BLUE}blue${RST}."

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Re:How does apt render its fancy progress bar? by mmphosis on Wednesday October 13, 2021 @05:34PM (#28857996)

  alias red='echo -ne "\e[31m"'
  alias yellow='echo -ne "\e[33m"'
  alias green='echo -ne "\e[32m"'
  alias blue='echo -ne "\e[34m"'
  alias cyan='echo -ne "\e[36m"'
  alias violet='echo -ne "\e[35m"'
  alias grey='echo -ne "\e[90m"'
  alias gray='echo -ne "\e[90m"'
  alias white='echo -ne "\e[37m"'
  alias bold='echo -ne "\e[1m"'
  alias flash='echo -ne "\e[7m\e[5m"'
  alias normal='echo -ne "\e(B\e[m"'

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