implement a timeout option for `read` ala bash's `read -t timeout`

[szpak]

It would be useful to have a mode for read to fail immediately when there is nothing to read from stdin.

As the simpler version of read -n 0 -t 0 (from Bash) there could be just a switch (-n? from no wait) to just return !=0 when there was nothing awaiting on stdin (instead of showing a prompt).

[szpak]

As it can be achieved with the following code I don't know if a read modification is really needed.

function myfunc
    if not tty >/dev/null
        read input
    else
        set input $argv
    end
    echo $input
end

[zanchey]

That's not quite the same thing; Bash's read -n 0 -t 0 checks if there is anything to read on STDIN, regardless of whether it is connected to a TTY or not.

Consider the pathological case echo -n | myfunc correct. This produces empty output instead of correct.

In Bash you could do

function myfunc {
    read -n 0 -t 0 input || input=$1
    echo $input;
}

[ravishi]

I just hit this issue while trying to do some tricks with STDIN. Any news on this front?

[ridiculousfish]

Nobody is working on it. What tricks were you hoping to do?

[floam]

Stuff that queries the terminal using VT or xterm commands where the terminal will reply by emitting stuff on stdin kind of needs a timeout in my experience.

[floam]

Simple example, capturing the resulting stdin of this is usually done with read with a maybe a 0.1s or less timeout on other shells. This is querying the configured background color:

printf \e]11\;?\a

It might "return" nothing at all, or maybe a very predictable escape, or a string that is unpredictable to us. I think there is actually no way to grab the output with fish.

[arigit]

this would be useful - if only to facilitate bash script porting, more compact code