From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 29868 invoked from network); 5 Jun 2020 01:54:54 -0000 Received: from ns1.primenet.com.au (HELO primenet.com.au) (203.24.36.2) by inbox.vuxu.org with ESMTPUTF8; 5 Jun 2020 01:54:54 -0000 Received: (qmail 5774 invoked by alias); 5 Jun 2020 01:54:33 -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: List-Unsubscribe: X-Seq: 45975 Received: (qmail 583 invoked by uid 1010); 5 Jun 2020 01:54:33 -0000 X-Qmail-Scanner-Diagnostics: from injection.crustytoothpaste.net by f.primenet.com.au (envelope-from , uid 7791) with qmail-scanner-2.11 (clamdscan: 0.102.3/25828. spamassassin: 3.4.4. Clear:RC:0(192.241.140.119):SA:0(-2.0/5.0):. Processed in 5.317293 secs); 05 Jun 2020 01:54:33 -0000 X-Envelope-From: sandals@crustytoothpaste.net X-Qmail-Scanner-Mime-Attachments: | X-Qmail-Scanner-Zip-Files: | Received-SPF: pass (ns1.primenet.com.au: SPF record at crustytoothpaste.net designates 192.241.140.119 as permitted sender) From: "brian m. carlson" To: zsh-workers@zsh.org Subject: [PATCH v2] exec: run final pipeline command in a subshell in sh mode Date: Fri, 5 Jun 2020 01:53:38 +0000 Message-Id: <20200605015338.1347787-2-sandals@crustytoothpaste.net> X-Mailer: git-send-email 2.27.0.278.ge193c7cf3a9 In-Reply-To: <20200605015338.1347787-1-sandals@crustytoothpaste.net> References: <20200605015338.1347787-1-sandals@crustytoothpaste.net> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit zsh typically runs the final command in a pipeline in the main shell instead of a subshell. However, POSIX requires that all commands in a pipeline run in a subshell, but permits zsh's behavior as an extension. Since zsh may be used as /bin/sh in some cases (such as macOS Catalina), it makes sense to have the POSIX behavior when emulating sh, so do that by checking for being the final item of a multi-item pipeline and creating a subshell in that case. >From the comment above execpline(), we know the following: last1 is a flag that this command is the last command in a shell that is about to exit, so we can exec instead of forking. It gets passed all the way down to execcmd() which actually makes the decision. A 0 is always passed if the command is not the last in the pipeline. […] If last1 is zero but the command is at the end of a pipeline, we pass 2 down to execcmd(). So there are three cases to consider in this code: • last1 is 0, which means we are not at the end of a pipeline, in which case we should not change behavior. • last1 is 1, which means we are effectively running in a subshell, because nothing that happens due to the exec is going to affect the actual shell, since it will have been replaced. So there is nothing to do here. • last1 is 2, which means our command is at the end of the pipeline, so in sh mode we should create a subshell by forking. input is nonzero if the input to this process is a pipe that we've opened. At the end of a multi-stage pipeline, it will necessarily be nonzero. Note that several of the tests may appear bizarre, since most developers do not place useless variable assignments directly at the end of a pipeline. However, as the function tests demonstrate, there are cases where assignments may occur when a shell function is used at the end of a command. The remaining assignment tests simply test additional cases, such as the use of local, that would otherwise be untested. --- Src/exec.c | 10 ++++++---- Test/B07emulate.ztst | 22 ++++++++++++++++++++++ 2 files changed, 28 insertions(+), 4 deletions(-) diff --git a/Src/exec.c b/Src/exec.c index 29f4fc5ca..f2650f311 100644 --- a/Src/exec.c +++ b/Src/exec.c @@ -2866,11 +2866,13 @@ execcmd_exec(Estate state, Execcmd_params eparams, pushnode(args, dupstring("fg")); } - if ((how & Z_ASYNC) || output) { + if ((how & Z_ASYNC) || output || + (last1 == 2 && input && EMULATION(EMULATE_SH))) { /* - * If running in the background, or not the last command in a - * pipeline, we don't need any of the rest of this function to - * affect the state in the main shell, so fork immediately. + * If running in the background, not the last command in a + * pipeline, or the last command in a multi-stage pipeline + * in sh mode, we don't need any of the rest of this function + * to affect the state in the main shell, so fork immediately. * * In other cases we may need to process the command line * a bit further before we make the decision. diff --git a/Test/B07emulate.ztst b/Test/B07emulate.ztst index 7b1592fa9..45c39b51d 100644 --- a/Test/B07emulate.ztst +++ b/Test/B07emulate.ztst @@ -276,3 +276,25 @@ F:Some reserved tokens are handled in alias expansion 0:--emulate followed by other options >yes >no + + emulate sh -c ' + foo () { + VAR=foo && + echo $VAR | bar && + echo "$VAR" + } + bar () { + tr f b && + VAR="$(echo bar | tr r z)" && + echo "$VAR" + } + foo + ' + emulate sh -c 'func() { echo | local def="abc"; echo $def;}; func' + emulate sh -c 'abc="def"; echo | abc="ghi"; echo $abc' +0:emulate sh uses subshell for last pipe entry +>boo +>baz +>foo +> +>def