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Comment by micro_softy | Hacker News Reader

Apologies for being stupid but this does not make sense to me:

  while [ true ];do ssh user@62.141.55.117; sleep 0.1; done

Is this the same as writing:

  while test true; do ...; done

Then this would also work:

  while [ false ]; do ...; done

But if the plan is to use the keyboard e.g. INT to stop this loop, why test anything? One could just write:

  while :; do ...; done

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`test` is the oldest and most portable syntax, "[" is a POSIX synonym which is either a shell built-in (e.g. in bash) or a command i.e. /usr/bin/[ .

You are correct that the author seems to misunderstand what "[" and "test" do, probably by failed analogy with C syntax. In the case of "test foo" for any string "foo", "test" will be evaluating a non-empty expression which is always true.

For a vaguely similar use case (repeat till host is up) I once wrote

    until ssh ...; do sleep 5; done

which stops looping once a connection succeeds.

  while :;do ssh ... && break; sleep 5; done

Why? That reminds me of the

    while(1) {
        if (condition)
            break;
        ...
    }

stuff I've seen too much of and can't explain, instead of just while(!condition) { ... }.

I'm not much of C programmer but I think it's an approximation of an infinite loop.

   for(;;){
         if(condition) break;
   }

Yes, that looks exactly analogous, but my question is why people don't use the perfectly good built-in conditional termination in a while or for loop and instead add on an if statement.

(Also, I don't understand why a for(;;) loop is more attractive than a while(1) loop.)

There's always something to remark on other peoples use of bash, I often find.

For example I'd rather just do while command; do sleep 0.1; done.

Or simply install autossh.

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