Trailing whitespace after $'\0' with external commands

Trailing whitespace after $'\0' with external commands

[Eric Cook]

I've noticed trailing whitespace is ignored when it appears immediately
after $'\0'. i am unsure if this is intended behavior or not.

% zsh -c "/usr/bin/printf '<%s>' $'\0'' '; echo"
<>
% zsh -c "printf '<%s>' $'\0'' '; echo"
< >
% ksh93 -c "/usr/bin/printf '<%s>' $'\0'' '; echo"
< >
% ksh93 -c "printf '<%s>' $'\0'' '; echo"
<
>                                                                                                    

% ksh93 -c "type printf"
printf is a shell builtin
%

If the whitespace appears before the $'\0', it prints.
% zsh -c "/usr/bin/printf '<%s>' ' '$'\0'; echo"
< >
% zsh -c "printf '<%s>' ' '$'\0'; echo"
< >

Re: Trailing whitespace after $'\0' with external commands

[Eric Cook]

On 01/11/2014 05:18 PM, Eric Cook wrote:
> % ksh93 -c "printf '<%s>' $'\0'' '; echo"
> <
>
% ksh93 -c "printf '<%s>' $'\0'' '; echo"
< >

mangled email :P

Re: Trailing whitespace after $'\0' with external commands

[Bart Schaefer]

On Jan 11,  5:18pm, Eric Cook wrote:
} Subject: Trailing whitespace after $'\0' with external commands
}
} I've noticed trailing whitespace is ignored when it appears immediately
} after $'\0'. i am unsure if this is intended behavior or not.
} 
} % zsh -c "/usr/bin/printf '<%s>' $'\0'' '; echo"
} <>

This is /usr/bin/printf behavior, not zsh behavior.  Has nothing to do
with whitespace:

% zsh -fc "/usr/bin/printf '<%s>' $'\0''none of this'; echo"
<>
% zsh -fc "printf '<%s>' $'\0''none of this'; echo"
<none of this>

I can only conclude that ksh is not actually retaining the nul byte in
the argument list when calling /usr/bin/printf.  There's an argument
(no pun intended) to be made for this behavior, in that it's impossible
for a string passed through the argv mechanism of execve and friends to
contain an embedded nul; the string will always end at that byte, so
ksh assumes it knows better than you and removes it so that the called
program (/usr/bin/printf in this case) can see the "whole" string.

Conversely, zsh is just doing *exactly* what you told it to do.

Re: Trailing whitespace after $'\0' with external commands

[Eric Cook]

On 01/11/2014 06:35 PM, Bart Schaefer wrote:
> I can only conclude that ksh is not actually retaining the nul byte in
> the argument list when calling /usr/bin/printf.  There's an argument
> (no pun intended) to be made for this behavior, in that it's impossible
> for a string passed through the argv mechanism of execve and friends to
> contain an embedded nul; the string will always end at that byte, so
> ksh assumes it knows better than you and removes it so that the called
> program (/usr/bin/printf in this case) can see the "whole" string.
>
> Conversely, zsh is just doing *exactly* what you told it to do.
Ah, thank you for explaining it.