Current date in cal is not highlighted in recent Debian

Question

As answered in Highlight the current date in cal

the current date in output form cal is automatically highlighted (reverse colors) if the output goes to terminal.

That's what I had always been getting.

However, with my current Debian GNU/Linux, it is not the case any more, and I'm wondering what the fix is.

$ echo $TERM
xterm

$ lsb_release -a 
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux bullseye/sid
Release:        testing
Codename:       bullseye

Answer 1

I believe the correct "Answer" to this question is documented here on GitHub

To quote add

alias cal="if [ -t 1 ] ; then ncal -b ; else /usr/bin/cal ; fi"

into your shell rc file.

This is an extremely irritating change. Changing the behavior of a frequently used cli command for at least 17 years to make it "correct" is kind of insane. Now I understand why so many people hate Windows so much but are still reluctant to switch to Linux. I'm pretty sure almost all package maintainer who use cal (actually I think majority of them uses date anyway) are trained to use cal -h to turn off the highlight. Now the change even breaks compatibility with cal -h.

The change is documented here

A simpler hack to solve the "no highlight" is to alias cal to ncal -b, but it is not 100% correct with the package ncal maintainer's expectation.

Answer 2

cal -3 doesn't work after alias, this accepts options:

if [ -t 1 ] ; then alias cal="ncal -b" ; else alias cal="/usr/bin/cal" ; fi

Answer 3

I just wanted to add onto @ShiB's great answer with the following:

function cal() {
    if [ -t 1 ]; then ncal -b "${@}"; else command cal "${@}"; fi
}

Changes from @ShiB's answer:

1. Use a function instead of an alias to facilitate passing arguments to the command(s)
2. Replace /usr/bin/cal with command cal in case the user has cal installed in a non-standard location