From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17340 invoked by alias); 10 Dec 2015 04:18:54 -0000 Mailing-List: contact zsh-workers-help@zsh.org; run by ezmlm Precedence: bulk X-No-Archive: yes List-Id: Zsh Workers List List-Post: List-Help: X-Seq: 37370 Received: (qmail 16381 invoked from network); 10 Dec 2015 04:18:52 -0000 X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on f.primenet.com.au X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM, HTML_MESSAGE,T_DKIM_INVALID autolearn=ham autolearn_force=no version=3.4.0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=8SEKEn9XQmxTVgAxn6v0h/0cEfLoSkyLPJItAiY/lMQ=; b=kA64A8XuEw+7comCEh2u7RQ3jdb4LTwRqvgPJs2OcQcjwxIyLOQerDthQ03gTTgFri vBXD/8pkhg+tj99MmIb9JQu6nZ81ycMp0ePduGVreZg0Ho8NLUWJxmE1zHVzzAL68RiO hWiko4N+IUMe7IkrLZ4xcfUMrYxu6fA58W0W4mcxCDf/rjt/Q4NqQJIe953G0SHSkxDn 1ibfvHme1vx+hKdBFpx+t/i41azHDvR+1hxN6Ni10+Gj6bC5asY52D0T5nt8nXozkSSL F7DACH1sJ3FYFM+DyKJ0fZlCa781XQ6uNdWadneZdcWkxbc9p0MNY26MSGFNnAldHMzc 5znA== MIME-Version: 1.0 X-Received: by 10.107.185.196 with SMTP id j187mr9318556iof.151.1449721131254; Wed, 09 Dec 2015 20:18:51 -0800 (PST) In-Reply-To: <2007121449719799@web8h.yandex.ru> References: <2007121449719799@web8h.yandex.ru> Date: Thu, 10 Dec 2015 14:48:51 +1030 Message-ID: Subject: Re: expr length "$val" returns the wrong length for values containing NULL (\\0) From: D Gowers To: "Nikolay Aleksandrovich Pavlov (ZyX)" Cc: "zsh-workers@zsh.org" Content-Type: multipart/alternative; boundary=94eb2c0771240d493205268381fb --94eb2c0771240d493205268381fb Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Ah, okay. That (commandline arguments not being able to contain NUL) seems.. a bit anachronistic. But I guess it's never been enough of a problem to warrant the considerable bother to fix it. Fair enough. On Thu, Dec 10, 2015 at 2:26 PM, Nikolay Aleksandrovich Pavlov (ZyX) < kp-pav@yandex.ru> wrote: > > 10.12.2015, 04:52, "D Gowers" : > > Test case: > > > > v=3D$(printf foo\\0bar);expr length "$v";expr length $v > > > > alternatively: > > > > v=3Dfoo$'\0'bar;expr length "$v";expr length $v > > > > In zsh, the values returned are 3 and 3. > > In dash and zsh, the values returned are 6 and 6. > > > > Both of those results are wrong, AFAICS (foo$'0'bar is 7 characters > long). > > But the zsh result is more severely wrong. I could understand the > bash/dash > > result, at least, as 'NULL characters are not counted towards length'. > > Both results are *right*. In both cases you ask the length of the string > and you get it. > > In dash (also posh, bash and busybox ash) zero byte is skipped when > storing. So length of the $v *is* six. You may question whether it is rig= ht > storing without zero byte, but the fact that all four shells have exactly > the same behaviour makes me think this is part of the POSIX standard. In > any case non-C strings are not on the list of features of these shells > unlike zsh (it also internally uses C NUL-terminated strings, but zero > bytes and some other characters are =E2=80=9Cmetafied=E2=80=9D (i.e. esca= ped) and > unmetafied when passed to the outer world e.g. by doing `echo $v` to pass > string to terminal). > > As I said in zsh zero byte is stored. But C strings which are the only > ones that can be arguments to any program are **NUL-terminated**. So what > you do is passing string "foo" because NUL terminates the string. You > cannot possibly get the answer you think is right here thus, unless you > reimplement `expr` as a zsh function. > > > > > In any case, it is easily demonstrated that the string is not 3 > characters > > long, by running 'echo "$V"' or 'print "$v"' or 'echo ${#v}' > > > > `zsh --version` =3D 'zsh 5.2 (x86_64-unknown-linux-gnu)' > --94eb2c0771240d493205268381fb--