¬ just serendipity 🍀 (not just serendipity)

When using watch(1) to monitor program output, colors will not be emitted by default.

Thankfully watch(1) has a --color (or -c flag).

Still, when using it with e.g. node tests, colors are not emitted:

% watch --color -- node mytest.js
Every 2.0s: node ex5.js                       MacBookAir: 14:43:06
                                                     in 0.107s (0)
✔ toWasm (0.865792ms)
ℹ tests 1
ℹ suites 0
ℹ pass 1
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 3.8805

The command detects that it’s not attached to the terminal. :(

How can we force color output in this case?

There’s no universal answer:

• Set CLICOLOR=1, CLICOLOR_FORCE=1
• See whether the program has a --color flag. For example: git and ls both support --color=always.

Another possibility, which is program agnostic, is to use an utility such as unbuffer(1) from the TCL Expect package:

% watch --color -- unbuffer node mytest.js

The unbuffer solution is my favorite (previously).

Reference: Stack Overflow.