On Nov 03, 2007, at 12:43:06, Ahmed S. Darwish wrote:
Bashv3 builtin "echo" behaves very strangely to -EINVAL. It sends
all the buffers that causes -EINVAL again in subsequent echo
invocations.
i.e.
echo "Invalid Rule" > /smack/load # -EINVAL returned
echo "Valid Rule" > /smack/load
In seconod iteration, echo sends the first invalid buffer again
then sends the new one. This causes a "Invalid Rule\nValid Rule"
buffer sent to write().
IMHO, this is a bug in builtin echo. The external /bin/echo doesn't
cause such strange behaviour.
Actually, what causes problems here is something between a bug and a
feature in libc's buffering. Basically the -EINVAL error causes libc
to leave its data in the file-output buffer despite the file being
closed and reopened. Since a standalone echo just exits that buffer
is discarded, but for the bash builtin it hangs around in the buffer
for a while and ends up getting prepended to the following echo
statement. There's actually multiple ways to make this fail; this is
just the simplest.
Cheers,
Kyle Moffett
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