Ubuntu Terminal with alternating colours for each line

Question

I have poor eyesight that is getting worse and worse, and my work requires me to use a lot of terminal-based programmes with table-based outputs (see below). It can be very difficult to look at individual lines and access the information I need. I'm looking for a way to make the terminal show each line [EDIT:] of the background (i.e. where purple is default) in alternating colours in order to guide my eyes better. Is there a way to do this in the Ubuntu terminal, or another terminal programme that offers this option? I'm really struggling to find anything

[EDIT:]

@kos's response using this works with Xspec:

In ~/.bashrc:

alias colorize="perl -pe '
    if( \$. %2) {
        s/^/\e[38;5;15m/; s/^/\e[48;5;238m/
    }
    else {
        s/^/\e[38;5;0m/; s/^/\e[48;5;249m/
    }

    s/\$/\e[K/;
    s/\$/\e[0m/
'"

Usage:

<command> | colorize

However there is an issue where I cannot see my active prompt (i.e. "XSPEC12>") or what I'm typing in the prompt. Once I have hit enter, it shows up, but I can't see it whilst I'm typing

Answer 1

Use a background image

Unfortunately gnome-terminal no longer has background image feature, but e.g. Konsole still does. For Konsole it is set in profile settings by creating a new color scheme.

Create an image that has stripes at the same spacing as your terminal font. It is easiest to do this by taking a screenshot and drawing on top of it:

Set it as the terminal background and you have stripes in everything:

Downside is that the spacing will not scale if you zoom the terminal font. Though it is possible to create multiple profiles with different font settings and corresponding background images.

Answer 2

Ubuntu uses Gnome Terminal, which has an option to increase the space between its lines. The option is in the hamburger menu > Preferences > Profile > Text > Cell spacing > height:

Setting the cell height spacing to 1.4 changes the output from:

to this, where it may be easier to follow lines for you:

In the same settings, you can also increase the font size, which may also be helpful.

Answer 3

Try this:

Put this text into striped.py:

#!/usr/bin/env python3
# -*- coding: iso-8859-1 -*-

import sys

c = ['\x1b[36m', '\x1b[37m']  # alternate between these two, for odd/even lines.

print(
    ''.join([
        c[n%2] + line 
        for n,line in enumerate(sys.stdin)
        ]),
    '\n\x1b[0m'
    )

Make it executable by chmod 755 striped.py

And then use it as in e.g. maketable | ./striped.py

... which will print every other line in different color.

To use less with this output, add its -R option as in ... | less -R.

I tried to find a pair of colors that are distinguishable yet contrasting to each other.

Example to try out

$ striped.py < /etc/os-release | less -R

More

If you wish, you can have numbered lines; that can be done (in fancy fashion) by adding

rvson = '\x1b[7m'
rvsoff = '\x1b[27m'

on lines after c = ... and then change

c[n%2] + line

with + f'{rvson}{n:>4}:{rvsoff} ' inserted, as in...

c[n%2] + f'{rvson}{n:>4}:{rvsoff} ' + line

Alternative

Use dimmed text instead of colors; change the c = ... line to

c = ['\x1b[2m', '\x1b[22m']

Noted for this: Does not work in Windows/cmd.exe, it is simply ignored.

---

Ref: ANSI escape code - Wikipedia

---

For Windows cmd users: add

import os
os.system("")

e.g. on a line after import sys - this magically initializes (some) ANSI escape code support.

"That is the Windows way" - always some kind of special magic required.

---

Edit 2024-06-12:
Alternative: Make a striped background, using the "same" code as above.

#!/usr/bin/env python3
# -*- coding: iso-8859-1 -*-

import os
os.system("") # make this work in Win/cmd.exe

import sys

c = [
    '\x1b[48;2;80;80;80m',
    '\x1b[48;2;100;100;100m'
    ]

print(
    ''.join([
        c[n%2] + '\x1b[2K' + line 
        for n,line in enumerate(sys.stdin)
        ])+'\x1b[0m',end=''
    )
print()

Note:
*[48;2;80;80;80m has the 4 for background color (use 3 for foreground),
and ;80;80;80 for R, G, and B - as they're the same here we get a grey tone.

Any other RGB values will also work, i.e. create your own color-version in pink;
;255;0;255 is "full" pink (bright magenta), do reduce the 255's to get a less colorful tone. Chose two slightly different tones and place them as a and b in inside c = [ a, b ]

And last but not least + '\x1b[2K' + makes the background appear on the entire line, regardless of window size, line length or height - dependent only on c[n%2] to set the color.

Answer 4

Note: these are a good general solutions to colorize the output of a program. But they don't cope well with interactive shells, as each time you run a command in the interactive shell the prompt and the command will be drawn to the screen only after having hit enter. For use with interactive shells, see @jpa's solution.

---

Below are two solutions, both similar in concept to Hannu's solution (but using aliases and Perl);

One will colorize the text, the other will colorize both the text and the background;

Both require defining an alias in ~/.bashrc;

I chose white (\e[37m) and red (\e[31m) for the first option and white on dark grey (\e[38;5;15m / \e[48;5;238m) and black on light grey (\e[38;5;0m / \e[48;5;249m) for the second option, but you should probably choose your own colors based on which suit your eyesight the best.

The second option will require more extensive ANSI support from the terminal (it's going to be fine in gnome-terminal and most modern terminals though).

Option #1 (lighter approach): colorize the text

In ~/.bashrc:

alias colorize="perl -pe '\$. %2 ? s/^/\e[37m/ : s/^/\e[31m/; s/\$/\e[0m/'"

Usage:

<command> | colorize

Option #2 (heavier approach): colorize the text and the background

In ~/.bashrc:

alias colorize="perl -pe '
    if( \$. %2) {
        s/^/\e[38;5;15m/; s/^/\e[48;5;238m/
    }
    else {
        s/^/\e[38;5;0m/; s/^/\e[48;5;249m/
    }

    s/\$/\e[K/;
    s/\$/\e[0m/
'"

Usage:

<command> | colorize

---

The downside to using escape codes to colorize the output is that the output will be polluted with the escape codes; most of the time this won't be an issue, as the main purpose is obviously to run the alias to colorize the output to the terminal, however it's worth noting that, e.g., foo | colorize | tee >file will result in file containing the escape codes.