Re: echo do not print NUL byte

[Eric Blake <eblake@redhat.com>]

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On 01/20/2016 02:38 PM, Trek wrote:
> there is no way to print the NUL byte with the echo utility

POSIX says you should use 'printf', not 'echo', if you expect to use any
\ in the arguments.  That said, the man page says:

     echo [-n] args...
...
            \0digits
                    Output the character whose value is given by zero to
three
                    octal digits.  If there are zero digits, a nul character
                    is output.


> with dash (XSI, no -e argument):
> 
>   $ dash -c 'echo \\0 | od -An -c'
>     \n

So this is behavior in disagreement with the documentation, so you
definitely have discovered a bug.  Of course, since POSIX already says
the use of \ is implementation-defined if XSI is not in force, and dash
doesn't necessarily strive for full XSI compliance, it might be easier
to patch the docs than to output a NUL byte.

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


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