Re: [Qemu-devel] [PATCH] qemu-binfmt-conf.sh: add CPUS, add --reset, make -p and -c boolean (no arg)

[Eric Blake <eblake@redhat.com>]

On 3/5/19 1:15 PM, Unai Martinez Corral wrote:

>>> +      find /proc/sys/fs/binfmt_misc/ -type f -name 'qemu-*' -exec sh -c
>>> 'echo -1 > {}' \;
>>
>> echo -1 is not portable (you are not guaranteed that echo won't try to
>> treat it as an option); better would be using printf.
> 
> Incidentally, I tried with MSYS2 and fedora:29 docker container. On
> both of them , 'echo -1' works, while 'printf -1' does not. Anyway, I
> replaced it with 'printf %s -1'. Hope it is ok.

You are correct that 'printf -1' is likely to fail, 'printf -- -1' is 
portable but unusual, and 'printf %s\\n -1' is identical to the common 
(but non-portable) behavior of 'echo -1'. Is the newline important?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org