Re: [Help-bash] Interesting consequence of Bash's grammar

[Eric Blake]

On 08/27/2015 11:54 AM, Greg Wooledge wrote:
> On Thu, Aug 27, 2015 at 04:09:38PM +0000, Ioan-Andrei Bârsan wrote:
>> shell_command can, among other things, be the `{ ... }` group command, but
>> it can also be an if statement, or a while loop (see line 760). This means
>> that the following statement is legal Bash:
>>
>> bar () if true; then echo "I am a weird funciton."; fi
>>
>> Is this a known/intentional feature?
> 
> Yes.  Some people even use it on purpose, like:
> 
> foo() (
>   # This function always runs in a subshell, so we can run amok with
>   # transient side effects.
>   shopt -s stuff
>   cd somewhere
>   PATH=things
>   ...
> )

And it is required by POSIX:

http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_09_05

> The format of a function definition command is as follows:
> 
> fname() compound-command[io-redirect ...]

so changing the grammar to require {} would break conforming scripts.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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