Add parser-friendly output mode

[max-baz]

Hi,

First of all, love the tool, awesome idea!

I got interested to use progress as a framework for building other tools on top of it, specifically an indicator for my status panel that would show the currently running operations, and I found it quite difficult to parse the values out of the progress command. Hence this feature request 🙂

Just to give you an example, suppose I want to display on my status panel just the command name (cp, mv, etc.) and the current progress percentage, e.g. cp 73% rsync 25%. In addition, I want to exclude certain commands (e.g. gpg) and I want to exclude 0% and 100% values.

Here's the current code that is capable of doing that:

progress -q | sed 's/\[[^]]*\] //g' | awk 'BEGIN { ORS=" " } NR%3==1 { op=$1 } NR%3==2 { pct=($1+0); if (op != "gpg" && pct > 0 && pct < 100) { print op, $1 } }'

Not very readable, and took time to come up with.

What made it difficult to parse was this:

• Multiple lines per entry (specifically, three lines)
• No easy separator between columns (the most obvious idea is to split on space, but e.g. PID can be [12345] and [ 1234])

I stumbled upon this blog post, and I must say this would probably be ideal if progress had a --json flag, which would output everything in JSON format, which is standard, predictable, and super easy to parse with jq.

I also saw #131 and initially got excited by it, but then I realized it doesn't print all the fields, so it isn't really a solution.

What do you think about --json option?