*FLAWED* Re: busybox sed, 'r' command

[Cristian Ionescu-Idbohrn]

On Wed, 23 Mar 2016, Ralf Friedl wrote:
>
> On the other hand, I don't know why busybox sed needs exactly one space
> between command and filename. GNU sed works with zero or more spaces.

Good points, everyone.  Thanks.  Still...

# Note, the input file /tmp/bar lacks the <newline> on the last line

# simplified

GNU sed ignores open failure on not specified/not existing file:

$ strace sed 'r' /tmp/bar
open("/tmp/bar", O_RDONLY|O_LARGEFILE)  = 3
read(3, "foo\nbar\nbaz", 4096)          = 11
write(1, "foo\n", 4foo
)                    = 4
open("", O_RDONLY|O_LARGEFILE)          = -1 ENOENT (No such file or
directory)
write(1, "bar\n", 4bar
)                    = 4
open("", O_RDONLY|O_LARGEFILE)          = -1 ENOENT (No such file or
directory)
read(3, "", 4096)                       = 0
write(1, "baz\n", 4baz
)                    = 4
open("", O_RDONLY|O_LARGEFILE)          = -1 ENOENT (No such file or
directory)
read(3, "", 4096)                       = 0
close(3)                                = 0

busybox sed reports an error:

$ strace busybox sed 'r' /tmp/bar
write(2, "sed: empty filename\n", 20sed: empty filename
)   = 20

Arguably, this may look like a bug in GNU sed, or intentional
behaviour?

# Let's do a more reasonable test.

$ sed -n '1,$p' /tmp/bar | cat -E
foo$
bar$
baz
   ^
Note the missing <newline> char on the last line.

$ busybox sed -n '1,$p' /tmp/bar | cat -E
foo$
bar$
baz$
   ^
There's a <newline> char on the last line.

Which is at fault here?  I would say both (with reservations).
But obviously, non-determinism.

$ f=/tmp/bar && cat $f && [ -z "$(tail -c1 $f)" ] || echo

and:

$ f=/tmp/bar && cat $f && tail -c1 $f | read __ || echo

work, but they look more convoluted to me.


Cheers,

-- 
Cristian