How to have an in-place string that updates on stdout
go, stdout
Solution
`stdout` is a stream (`io.Writer`). You cannot modify what was already written to it. What can be changed is how that stream's represented in case it is printed to a terminal. Note that there's no good reason to assume this scenario. For example, a user could redirect stdout to a pipe or to a file at will.
So the proper approach is to first check:
- if the stdout is going to a terminal
- what is that terminal's procedure to overwrite a line/screen
Both of the above are out of this question's scope, but let's assume that a terminal is our device. Then usually, printing:
fmt.Printf("\rOn %d/10", i)
will overwrite the previous line in the terminal. `\r` stands for `carriage return`, implemented by many terminals as moving the cursor to the beginning of the current line, hence providing the "overwrite line" facility.
As an example of "other" terminal with a differently supported 'overwriting', here is an example at the playground.
Problem
I want to output to stdout and have the output "overwrite" the previous output. For example; if I output `On 1/10`, I want the next output `On 2/10` to overwrite `On 1/10`. How can I do this?