On Tue, Mar 02, 2021 at 08:24:20AM -0500, Sean Anderson wrote: > On 3/2/21 8:20 AM, Tom Rini wrote: > > On Mon, Mar 01, 2021 at 06:07:36PM -0500, Sean Anderson wrote: > > > On 3/1/21 1:26 PM, Heinrich Schuchardt wrote: > > > > On 3/1/21 3:17 PM, Tom Rini wrote: > > > > > On Sun, Feb 28, 2021 at 06:51:53PM -0500, Sean Anderson wrote: > > > > > > On 2/28/21 6:40 PM, Heinrich Schuchardt wrote: > > > > > > > Am 28. Februar 2021 22:29:51 MEZ schrieb Sean Anderson > > > > > > > <sean...@gmail.com>: > > > > > > > > If there were no variable substitutions in a command, then > > > > > > > > initial > > > > > > > > assignments would be misinterpreted as commands, instead of > > > > > > > > being > > > > > > > > skipped > > > > > > > > over. This is demonstrated by the following example: > > > > > > > > > > > > > > > > => foo=bar echo baz > > > > > > > > > > > > > > The commit message does not explain why this patch is needed. > > > > > > > > > > > > This is a bug I noticed while writing some tests of hush. > > > > > > > > > > > > > What shall be the value off foo after this line? > > > > > > > > > > > > It should be bar. This is an existing difference when compared with > > > > > > bash. For example, without this patch, we have > > > > > > > > > > > > => foo=bar echo $foo > > > > > > bar > > > > > > => echo $foo > > > > > > bar > > > > > > > > This seems really awkward. In bash I get: > > > > > > > > $ foo=bar ./test.sh > > > > bar > > > > $ echo $foo > > > > > > > > $ > > > > > > > > Where test.sh > > > > > > > > #!/bin/sh > > > > echo $foo > > > > > > > > I did not expect an assignment made before a command to stick. > > > > > > Yeah, this is because hush does not have the concept of per-command > > > assignments (scope). So everything happens in the global scope. > > > > > > > > > > > > > > > > > > > > > > > What will be the output of > > > > > > > > > > > > > > foo=bar echo ${foo} > > > > > > > > > > > > > > with and without your patch? > > > > > > > > > > > > It is the same. > > > > > > > > Please, provide an example where the patch makes a difference. > > > > > > > > Best regards > > > > > > > > Heinrich > > > > > > > > > > > > > > bash works as you describe. dash and busybox-sh both function like > > > > > this: > > > > > $ foo=bar echo $foo > > > > > > > > > > $ echo $foo > > > > > > > > > > $ > > > > > > > > > > That we error out entirely is different from everyone. Is that a good > > > > > thing? Maybe. I know I've caught myself making thinkos due to that > > > > > logic. It does also violate the principal of least surprise, that we > > > > > don't act like anything else. But I would suggest the behavior of > > > > > busybox-sh (what we forked long long ago) is what we should model here > > > > > rather than be more bash-like. I'm not all that firm on this opinion > > > > > frankly, especially given the one-line nature of the change to bring > > > > > us > > > > > that behavior and I assume dash/busybox are acting like pure sh would > > > > > in > > > > > this case, which we aren't anyhow. > > > > > > Ok, I'd like to clear things up. Here is the current behavior of U-Boot: > > > > > > > > > => foo=bar echo $foo > > > bar > > > => echo $foo > > > bar > > > => baz=bar echo qux > > > Unknown command 'baz=bar' - try 'help' > > > > I see this as well (which isn't what I said in another part of this > > thread, so I re-checked just now). > > > > > with this patch, this changes to > > > > > > => foo=bar echo $foo > > > bar > > > => echo $foo > > > bar > > > => baz=bar echo qux > > > qux > > > > > > This patch *only* affects cases where there is an assignment at the > > > beginning of the line, but there is *no* variable reference in the > > > command. I know this is an edge case, but the current logic is clearly > > > wrong here. > > > > OK. But I don't see that behavior in bash 4.4.20 (Ubuntu 18.04). Where > > does one get a shell that works like you're changing our hush to? > > > > I'm not changing hush to work like the first two examples, it's already like > this. > > Only the third example is affected by this patch.
OK. But to what end? Historically we have a buggy but mostly compatible "hush" that acts like "sh" does. A more flexible shell could solve a lot of different use cases including making boot scripts that people end up writing being clearer and easier to write/debug/maintain. What I worry about here is making our shell not act like any regular shell people use. -- Tom
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