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=-3.3 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 29894 invoked from network); 7 Dec 2022 00:47:13 -0000 Received: from zero.zsh.org (2a02:898:31:0:48:4558:7a:7368) by inbox.vuxu.org with ESMTPUTF8; 7 Dec 2022 00:47:13 -0000 ARC-Seal: i=1; cv=none; a=rsa-sha256; d=zsh.org; s=rsa-20210803; t=1670374033; b=HhJPcKBQFHVLwuSsfxiuM+pUgR1BJ5J2TGKbVdYXslnXpwrJhsnJY5G08KYzYZXqdMCVKTuWBD jdWUTuy0jXIGITLKIlZFZF5rMGrBzH0bDhLY5yywobVwmq/wwYO5ii1NIz+lYs9VAQljbdDPQu zTgViUgOa8Hawf96XcbZYRJiVM7hg9GurkemJLNyIv+iKLgj6YQvq5gjR3Wrtl80cb+0+tIuVU VTMgEtZCRf2TxhOxTcihcvHhNuDbuW1NLtHumDfnJA2C5TI8O94aQHXPVaeiXpC3lYL2ywsfXW b8wzRsLYnkcAYdqDnaWQ781PDLCJbrQyZDuBDlW3LPsEZQ==; ARC-Authentication-Results: i=1; zsh.org; iprev=pass (mail-ej1-f49.google.com) smtp.remote-ip=209.85.218.49; dkim=pass header.d=brasslantern-com.20210112.gappssmtp.com header.s=20210112 header.a=rsa-sha256; dmarc=none header.from=brasslantern.com; arc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed; d=zsh.org; s=rsa-20210803; t=1670374033; bh=OQ7bWbTnyNZM72cll8ti0Iu1ARZsOKd0TvTDE6hxnWI=; h=List-Archive:List-Owner:List-Post:List-Unsubscribe:List-Subscribe:List-Help: List-Id:Sender:Content-Transfer-Encoding:Content-Type:To:Subject:Message-ID: Date:From:In-Reply-To:References:MIME-Version:DKIM-Signature:DKIM-Signature; b=QcTWPMaGiopr8H8/Se1Ytgfd0Z0/gXE6X6Zc+uCXP/yuSxW17MLHa3HabdAEuP/JePiELGGGFZ 0yQd7tlMv2EkLNO5bzYFVcGYhvJQIcgHMJ7l3vJtlV3EjtG6U8dRC0lUJJPoa7I3xzYfk5sEVy Esqb2pwuSM4nayRZ5B6aEvjK0sD4FdUSXOhtjIonfLhnA3XWb0HVwy+RvEWVvOCjgTwSy2aMnZ x1d6JDGiH9yjqb6s+71eTqi+TX8vyfEkdn/MiCJvuUUFhBfmxCkwUkLSnbYZAdN1oaosa8sU/0 jvGd5k9kxTbJtoBrj+Lmr1b2cf+0UwM/jYJumpZdDc9hNQ==; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=zsh.org; s=rsa-20210803; h=List-Archive:List-Owner:List-Post:List-Unsubscribe: List-Subscribe:List-Help:List-Id:Sender:Content-Transfer-Encoding: Content-Type:To:Subject:Message-ID:Date:From:In-Reply-To:References: MIME-Version:Reply-To:Cc:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID; bh=OQ7bWbTnyNZM72cll8ti0Iu1ARZsOKd0TvTDE6hxnWI=; b=CImgUmyx491U82siZ4AmTAyuMv oYqqeskp/jfSW2/Biqxu3+4WFEN5Q58uH61yB3C1ryRR6UEIUKgJpyoiZInq9gEyesZ4w6JWr1O5E JOsdDIA8DqkdX3fDoDuOUnV/6y7xROMDeJtYy1L02w1Z20KgsSkFrSjsZNy/ldFJpXtL21PBGGX+Z RqBWraDdJwcObYlYFCiYKIDY02xJOnscA3lTXldEPGgoImz31RDP8eQ97k8DQkrTzrJsVtWFJ976e 60J1lcDPuSY7xsG0XnWWaw2k/9AMk33RvetejKsA9EBBPg5qfZVDJS6aYtEg0GV2uiPavoB2ynstn jsIFmZ+Q==; Received: by zero.zsh.org with local id 1p2iaf-000Kqm-91; Wed, 07 Dec 2022 00:47:13 +0000 Authentication-Results: zsh.org; iprev=pass (mail-ej1-f49.google.com) smtp.remote-ip=209.85.218.49; dkim=pass header.d=brasslantern-com.20210112.gappssmtp.com header.s=20210112 header.a=rsa-sha256; dmarc=none header.from=brasslantern.com; arc=none Received: from mail-ej1-f49.google.com ([209.85.218.49]:39463) by zero.zsh.org with esmtps (TLS1.3:TLS_AES_128_GCM_SHA256:128) id 1p2ia4-000KZM-DM; Wed, 07 Dec 2022 00:46:37 +0000 Received: by mail-ej1-f49.google.com with SMTP id gh17so10374898ejb.6 for ; Tue, 06 Dec 2022 16:46:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=brasslantern-com.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=OQ7bWbTnyNZM72cll8ti0Iu1ARZsOKd0TvTDE6hxnWI=; b=JMwCUcsjKR76g6iPBkui1NSfeB0YOR8SVg3nOloI8awLEN2ZIH0VwBwVNVmEw+/761 WQk5fe8gg1EgldYj1r1pNgZhU7RpU7gvW0rQ2eoEA1E77SVfCW1pV8PAaJ/KLj5Z0KzN rWjh+b0GtnnEkffZAQlT7mcMPkpIGXOCBTrtAYcRHN1NeNu/BdVpMlo6q5IXyyYztdm4 eWFBHExwOoXerWBa339xi91QGfMIXRWthJr0sbDit5ZRCSkTBThFEtqdNYdlJZu65FGb 4jFnpSKEZj79USSA1RuqiSOXHQ8gEbHac0Shao6a9TqbXwI0vVUUCltflzFvPx8rsFYA B2Mg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=OQ7bWbTnyNZM72cll8ti0Iu1ARZsOKd0TvTDE6hxnWI=; b=oWhnMEWCZTbRDwZ6lE69UOSycdf7NsZNvTR8VggvPbSqdqSNUaeIK7pRIxUPW7b6hz mZRmgMFPJ5ETgzlrtKlUAGVuo5X1BlPnLryav9fraUoohDyThx/JU4H9QaKrEVkmKHp4 2jmv5pnJ7z2N0k8D92Az1Np9sx38yPE40TXPvfFyM4D3//Y9tLTytM8SmwPi7lnB7uVx LSH4LzCwnNjf4wAOkV5q1BgoRGSLdrlpK19y3bwa/GLzjNMif2bCrpDqzKvDtWNAqqPk VyVhVn5kyHPPkmzIJrEx5SfTBIc3Hdfe5BMbF4zuZFY3itcY1WIG1EAOWTMImxj5r1dv VWMQ== X-Gm-Message-State: ANoB5plQ9Jz8aZYv64rgMyGqXggYTQ/mPbC5lb1bwnZpvlteGI4+GHDC NoBqYYOi5ESPMs2O/pMRtlIFZS1A6FEpJmfH+pYHCgKGOIXQKQ== X-Google-Smtp-Source: AA0mqf7gxhJws3nVeQY545ObsBlKFw8+wOSxHoMmBKvHtVmQwCz+XC/znobT1cDjppilCN2O/3TDi62YfGpc0eyF1Dk= X-Received: by 2002:a17:906:1d59:b0:7c0:5496:4f1b with SMTP id o25-20020a1709061d5900b007c054964f1bmr34402514ejh.715.1670373996065; Tue, 06 Dec 2022 16:46:36 -0800 (PST) MIME-Version: 1.0 References: <54bcd6dd-e589-4696-f042-1155b78df9d2@eastlink.ca> <819c9630-f315-8b1c-cb52-3d3ae8de2d5c@eastlink.ca> <7eadf163-da34-d90b-61ce-b527fb75b597@eastlink.ca> <37b2456f-0459-4b85-74d1-bb380715e2ed@eastlink.ca> <21586f92-9a78-419c-84e5-f203a6f069b6@app.fastmail.com> In-Reply-To: <21586f92-9a78-419c-84e5-f203a6f069b6@app.fastmail.com> From: Bart Schaefer Date: Tue, 6 Dec 2022 16:46:24 -0800 Message-ID: Subject: Non-forking command substitution To: Zsh hackers list Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Seq: 51107 Archived-At: X-Loop: zsh-workers@zsh.org Errors-To: zsh-workers-owner@zsh.org Precedence: list Precedence: bulk Sender: zsh-workers-request@zsh.org X-no-archive: yes List-Id: List-Help: , List-Subscribe: , List-Unsubscribe: , List-Post: List-Owner: List-Archive: Redirecting to zsh-workers. On Tue, Dec 6, 2022 at 3:54 PM Lawrence Vel=C3=A1zquez wro= te: > > On Tue, Dec 6, 2022, at 1:55 PM, Roman Perepelitsa wrote: > > That said, it's totally possible to extend zsh with something like $[ > > ... ] which would work like $( ... ) but without forking. It would run > > the commands in another thread within the same process. > > FWIW, ksh has a ${ list;} construct that avoids a subshell: The "when followed by a space ${ starts a command, otherwise it's a parameter reference" is a bit odd, but I guess not odder than some of the things we do. Based on some random poking at ksh93, this construct does two things: 1. Switches from fork-to-the-right (bash, older sh) behavior to fork-to-the-left (zsh) behavior for pipes, so the rightmost part of a pipeline may run in the current shell. 2. If the rightmost thing is a builtin, captures/substitutes its output instead of printing it to stdout, otherwise acts exactly like $(...) Neither of those things actually requires a separate thread, though it does require some engineering down in the guts of builtin commands to replace simple stdio handling. It'd be interesting to know how ksh93 handles the ^Z/fg issues with left-forking that were recounted in recent -workers discussion.