Re: [BUG] builtin echo doesn't check write error

[Vincent Lefevre <vincent@vinc17.net>]

On 2021-06-24 10:47:39 +0200, Vincent Lefevre wrote:
> Note also about the bug in echo/print/etc., this actually seems
> to affect *all* builtins. For instance:
> 
> zira% (exec >&-; echo)
> zsh: write error: bad file descriptor
> zira% (exec >&-; echo >&-)
> zira% (exec >&-; print)
> zsh: write error: bad file descriptor
> zira% (exec >&-; print >&-)
> zira% (exec >&-; printf "\n")
> zsh: write error: bad file descriptor
> zira% (exec >&-; printf "\n" >&-)
> zira% (exec >&-; pwd)
> zsh: write error: bad file descriptor
> zira% (exec >&-; pwd >&-)
> zira% (exec >&-; history)
> zsh: write error: bad file descriptor
> zira% (exec >&-; history >&-)
> zira% 

That was about the error messages. But in all cases, the exit status
is 0:

zira% (exec >&-; echo; echo $? >&2)
zsh: write error: bad file descriptor
0
zira% (exec >&-; echo >&-; echo $? >&2)
0
zira% (exec >&-; print; echo $? >&2)
zsh: write error: bad file descriptor
0
zira% (exec >&-; print >&-; echo $? >&2)
0
zira% (exec >&-; pwd; echo $? >&2)
zsh: write error: bad file descriptor
0
zira% (exec >&-; pwd >&-; echo $? >&2)
0
zira% (exec >&-; history; echo $? >&2)
zsh: write error: bad file descriptor
0
zira% (exec >&-; history >&-; echo $? >&2)
0

The other shells differ, but for ksh, posh and busybox sh, in an
inconsistent way (I assume that this is a bug in these shells):

$ zsh -c 'exec >&-; echo; echo $? >&2; pwd; echo $? >&2'
zsh:1: write error: bad file descriptor
0
zsh:1: write error: bad file descriptor
0

$ sh -c 'exec >&-; echo; echo $? >&2; pwd; echo $? >&2'
sh: 1: echo: echo: I/O error
1
sh: 1: pwd: pwd: I/O error
1

$ bash -c 'exec >&-; echo; echo $? >&2; pwd; echo $? >&2'
bash: line 1: echo: write error: Bad file descriptor
1
bash: line 1: pwd: write error: Bad file descriptor
1

$ yash -c 'exec >&-; echo; echo $? >&2; pwd; echo $? >&2'
echo: cannot print to the standard output: Bad file descriptor
1
pwd: cannot print to the standard output: Bad file descriptor
1

$ busybox sh -c 'exec >&-; echo; echo $? >&2; pwd; echo $? >&2'
sh: write error: Bad file descriptor
1
1

(for busybox sh, the inconsistency is on the presence of the
error message).

$ ksh93 -c 'exec >&-; echo; echo $? >&2; pwd; echo $? >&2'
1
0

$ mksh -c 'exec >&-; echo; echo $? >&2; pwd; echo $? >&2'
1
0

$ posh -c 'exec >&-; echo; echo $? >&2; pwd; echo $? >&2'
1
0

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)