From unknown Mon Aug 18 15:38:28 2025 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-Mailer: MIME-tools 5.509 (Entity 5.509) Content-Type: text/plain; charset=utf-8 From: bug#70477 <70477@debbugs.gnu.org> To: bug#70477 <70477@debbugs.gnu.org> Subject: Status: tail command does not hang on /dev/random Reply-To: bug#70477 <70477@debbugs.gnu.org> Date: Mon, 18 Aug 2025 22:38:28 +0000 retitle 70477 tail command does not hang on /dev/random reassign 70477 coreutils submitter 70477 Ionut Nicula severity 70477 normal thanks From debbugs-submit-bounces@debbugs.gnu.org Fri Apr 19 19:05:37 2024 Received: (at submit) by debbugs.gnu.org; 19 Apr 2024 23:05:37 +0000 Received: from localhost ([127.0.0.1]:60865 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1rxxIU-0001pD-Is for submit@debbugs.gnu.org; Fri, 19 Apr 2024 19:05:37 -0400 Received: from lists.gnu.org ([2001:470:142::17]:33238) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1rxtAc-00049Q-6G for submit@debbugs.gnu.org; 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Fri, 19 Apr 2024 11:40:46 -0700 (PDT) MIME-Version: 1.0 From: Ionut Nicula Date: Fri, 19 Apr 2024 21:40:35 +0300 Message-ID: Subject: tail command does not hang on /dev/random To: bug-coreutils@gnu.org Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2607:f8b0:4864:20::536; envelope-from=nicula.iccc@gmail.com; helo=mail-pg1-x536.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-Spam-Score: 1.0 (+) X-Debbugs-Envelope-To: submit X-Mailman-Approved-At: Fri, 19 Apr 2024 19:05:09 -0400 X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: debbugs-submit-bounces@debbugs.gnu.org Sender: "Debbugs-submit" X-Spam-Score: -0.0 (/) The following command hangs indefinitely, as expected: tail -c 4096 /dev/random The following command immediately returns 4097 bytes, unexpectedly: tail -c 4097 /dev/random Details: - Source code obtained from: git://git.sv.gnu.org/coreutils - Commit id: 9ab1f9db94479eca4dd2c29b4e21550ff2bcd5bb - System: $ uname -a Linux zinc 6.1.0-20-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.85-1 (2024-04-11) x86_64 GNU/Linux From debbugs-submit-bounces@debbugs.gnu.org Sat Apr 20 00:52:45 2024 Received: (at 70477-done) by debbugs.gnu.org; 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c=relaxed/relaxed; d=cs.ucla.edu; s=9D0B346E-2AEB-11ED-9476-E14B719DCE6C; t=1713588740; bh=l0biNtacPU1s/F2N2jE0Lf1u9KPgFI/yvQGHfCSG0Rk=; h=Message-ID:Date:MIME-Version:To:From; b=G4X0hPl/B1C1aBGCeq6kWui5TShj9uJsIcLf7L1mH5n8DONGaWXtwbOxwFzd3hCf2 eQImDm8Y+SPFTq+NUQq4aZ/rgACU63RBX06fugyhPAixaq9eQZ5viHm8uRpoKfnF5c 9nAJX+MW4rPf69d4Ds3qaLj/fcLwg9jVScaXyVe2pg5O3Q+B7G78PetbEwItovUuk0 KenJkY1fGcDRNpeMA2f6W6FQkz0UZ5BoczM20Icrutmq53QuyBWk3BejhOKkBH6Ygq vDK7IXwXdXDS8zhZ92pQmBjXGKndIZLFaAIXSikyFgeiM2CZtlHGedHiKd/+Z1CNvl TE6TifXxu1+8g== X-Virus-Scanned: amavis at mail.cs.ucla.edu Received: from mail.cs.ucla.edu ([127.0.0.1]) by localhost (mail.cs.ucla.edu [127.0.0.1]) (amavis, port 10026) with ESMTP id ZXt--y7ux6p1; Fri, 19 Apr 2024 21:52:20 -0700 (PDT) Received: from [192.168.254.12] (unknown [47.154.17.165]) by mail.cs.ucla.edu (Postfix) with ESMTPSA id 4EB653C01409E; Fri, 19 Apr 2024 21:52:20 -0700 (PDT) Content-Type: multipart/mixed; boundary="------------fmvvErX0ZrPu0uXds2z9SxqL" Message-ID: Date: Fri, 19 Apr 2024 21:52:20 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: bug#70477: tail command does not hang on /dev/random To: Ionut Nicula References: Content-Language: en-US From: Paul Eggert Organization: UCLA Computer Science Department In-Reply-To: X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 70477-done Cc: 70477-done@debbugs.gnu.org X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: debbugs-submit-bounces@debbugs.gnu.org Sender: "Debbugs-submit" X-Spam-Score: -1.0 (-) This is a multi-part message in MIME format. --------------fmvvErX0ZrPu0uXds2z9SxqL Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024-04-19 11:40, Ionut Nicula wrote: > The following command hangs indefinitely, as expected: > > tail -c 4096 /dev/random > > The following command immediately returns 4097 bytes, unexpectedly: > > tail -c 4097 /dev/random Thanks for the bug report. Although the two commands should behave similarly, neither should loop: they should both output the requested number of random bytes. Similarly for /dev/zero. I installed the attached patch to do that. --------------fmvvErX0ZrPu0uXds2z9SxqL Content-Type: text/x-patch; charset=UTF-8; name="0001-tail-avoid-infloop-with-c-on-dev-zero.patch" Content-Disposition: attachment; filename="0001-tail-avoid-infloop-with-c-on-dev-zero.patch" Content-Transfer-Encoding: base64 RnJvbSBmYjU0M2I2YjgyYzFmM2EyMGZmODhmNDRjYzNlZDM2N2JmZTgxMWI2IE1vbiBTZXAg MTcgMDA6MDA6MDAgMjAwMQpGcm9tOiBQYXVsIEVnZ2VydCA8ZWdnZXJ0QGNzLnVjbGEuZWR1 PgpEYXRlOiBGcmksIDE5IEFwciAyMDI0IDIxOjQ0OjMyIC0wNzAwClN1YmplY3Q6IFtQQVRD SF0gdGFpbDogYXZvaWQgaW5mbG9vcCB3aXRoIC1jIG9uIC9kZXYvemVybwoKUHJvYmxlbSBy ZXBvcnRlZCBieSBJb251dCBOaWN1bGEgaW46Cmh0dHBzOi8vYnVncy5nbnUub3JnLzcwNDc3 Ciogc3JjL3RhaWwuYyAodGFpbF9ieXRlcyk6IERvIG5vdCBsb29wIGZvcmV2ZXIgb24gY29t bWFuZHMKbGlrZSAndGFpbCAtYyA0MDk2IC9kZXYvemVybycuCiogdGVzdHMvdGFpbC90YWls LWMuc2g6IFRlc3QgdGhpcyBmaXguCi0tLQogTkVXUyAgICAgICAgICAgICAgICAgfCAgMyAr KysKIHNyYy90YWlsLmMgICAgICAgICAgIHwgMjQgKysrKysrKysrKysrKysrKysrKy0tLS0t 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