Bel in PuTTYwhen it is waiting for input?

Question

I often have to download, update and build large projects due to which there is a long waiting period between 2 commands. The projects are stored and used on a linux machine, and i connect remotely to it using PuTTY.

Looking for a way to be alerted when a command is done, while i keep working on something else.

I am not expecting below approach, as the command itself may wait for input.

<command> && tput bel

Thanks.

Answer 1

PuTTY doesn't know when a remote command is waiting for input. As far as the terminal (or the SSH client) is concerned, input can always be sent. (Even trying to guess based on shown text is futile since many progress displays are indistinguishable to a computer from input prompts.)

Given your requirements, the only option I can think of is a LD_PRELOAD library that prints a bell whenever any program tries to read from a tty device. Something like:

#define _GNU_SOURCE
#include <dlfcn.h>
#include <unistd.h>

ssize_t read(int fd, void *buf, size_t count) {
    static ssize_t (*real_read)(int fd, void *buf, size_t count);

    if (isatty(fd))
        write(fd, "\a", 1);

    if (!real_read)
        real_read = dlsym(RTLD_NEXT, "read");

    return real_read(fd, buf, count);
}

(Well, it doesn't work for any statically-linked binary, but close enough.)

Then again, if a command waits for input, then it is by definition not done, so the requirements are somewhat contradictory.

Answer 2

As a 90% solution, you can tell your shell to echo a bell when a command completes. For instance, in bash, simply include \a in your PS1.

If you'd like a bell when the command stops to ask for input, a 99% solution is available in non-Linux Unixen: hit Ctrl-Y after running your command. Lacking support for that, though, try looking for program-specific configurations. For instance, in Vim, you can add norm \ to your .vimrc to echo a bell whenever it is launched.