tag 23239 notabug thanks On 04/07/2016 01:27 PM, Faissal Bensefia wrote: > Hey, > I stumbled across a bug in GNU coreutils' echo, if I use echo with an > option like -nn or -nnnnnnn it should be treated as something echoable > and echo "-nnnnnnn\n" but it doesn't, instead it takes it as an -n > argument and just doesn't echo with a newline. If I were to however put > a character that is not an 'n' in the long string of ns it does echo it > as it should. POSIX says it is not portable to use 'echo' with ANY string that starts with '-': http://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html and that you should favor printf instead. Furthermore, it states that the magic -n option (which has implementation-defined behavior) MUST be spelled exactly '-n' (and not '-nnnn'), to trigger the XSI behavior. Any other spelling has undefined results. So in coreutils, we've taken the following approach: by default, parse the options the same way getopt() always does; ANY sequence of options is treated as that option. In your case, you get the same as if you had specified multiple '-n' options: $ /bin/echo -nnn hi | od -tx1 -An 68 69 But if you don't like the default, then ask for POSIX compliance: $ POSIXLY_CORRECT=1 /bin/echo -nnn hi | od -tx1 -An 2d 6e 6e 6e 20 68 69 0a where we explicitly honor EXACTLY '-n'. As such, I don't see any problem with our current behavior, and am closing out this bug report. But feel free to add further comments. Also, there's a big long thread recently in the Austin Group: http://thread.gmane.org/gmane.comp.standards.posix.austin.general/12097 which concludes that POSIX is probably over-strict (by requiring exactly '-n', it forbids the relatively common '-e', '-E' and even '-ne' or '-en' options), but that changing the wording is an uphill battle: > echo "---- cut here ----" is perfectly safe and the standard > should not be changed to imply that it is not safe. For this > reason, I believe there is zero chance that Robert's wording > will achieve consensus. To be accepted, the new wording will > need to add only a narrow set of cases to the implementation- > defined behaviour. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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