# git-bisect: weird usage of read(1) 15 messages from 2008-08-11 to 2008-08-11. Participants: Francis Moreau, Johannes Schindelin, Mikael Magnusson, Reece Dunn, René Scharfe, Petr Baudis, Junio C Hamano. Thread: https://gitlist.dev/t/14930 ## Francis Moreau, 2008-08-11 13:57 Subject: git-bisect: weird usage of read(1) Message-ID: <38b2ab8a0808110657y24ac9526wca4acea3bddaec00@mail.gmail.com> URL: https://gitlist.dev/e/38b2ab8a0808110657y24ac9526wca4acea3bddaec00%40mail.gmail.com ``` Hello I found this in git bisect: printf >&2 'Are you sure [Y/n]? ' case "$(read yesno)" in [Nn]*) exit 1 ;; esac which looks very weird since read(1) returns a status and not the string reads from std input. Am I missing something ? Thanks -- Francis ``` ## Johannes Schindelin, 2008-08-11 14:15 Subject: Re: git-bisect: weird usage of read(1) Message-ID: URL: https://gitlist.dev/e/alpine.DEB.1.00.0808111615260.24820%40pacific.mpi-cbg.de.mpi-cbg.de In-Reply-To: <38b2ab8a0808110657y24ac9526wca4acea3bddaec00@mail.gmail.com> ``` Hi, On Mon, 11 Aug 2008, Francis Moreau wrote: > I found this in git bisect: > > printf >&2 'Are you sure [Y/n]? ' > case "$(read yesno)" in [Nn]*) exit 1 ;; esac > > which looks very weird since read(1) returns a status and not the > string reads from std input. > > Am I missing something ? Yes. "$()" does not return the status, but the output. Ciao, Dscho ``` ## Mikael Magnusson, 2008-08-11 14:16 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <237967ef0808110716l2a0a2a4je22c2a1b8c239f57@mail.gmail.com> URL: https://gitlist.dev/e/237967ef0808110716l2a0a2a4je22c2a1b8c239f57%40mail.gmail.com In-Reply-To: ``` 2008/8/11 Johannes Schindelin : > Hi, > > On Mon, 11 Aug 2008, Francis Moreau wrote: > >> I found this in git bisect: >> >> printf >&2 'Are you sure [Y/n]? ' >> case "$(read yesno)" in [Nn]*) exit 1 ;; esac >> >> which looks very weird since read(1) returns a status and not the >> string reads from std input. >> >> Am I missing something ? > > Yes. "$()" does not return the status, but the output. But there is no output, since read doesn't print anything... case "$(read yesno; echo $yesno)" in [Nn]*) could work, but looks a bit strange. read yesno; case $yesno in [Nn]*) would be the usual way to do things i think? -- Mikael Magnusson ``` ## Francis Moreau, 2008-08-11 14:18 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <38b2ab8a0808110718x2f63608ga3d2d77e317ce4eb@mail.gmail.com> URL: https://gitlist.dev/e/38b2ab8a0808110718x2f63608ga3d2d77e317ce4eb%40mail.gmail.com In-Reply-To: ``` Hello On Mon, Aug 11, 2008 at 4:15 PM, Johannes Schindelin wrote: > Hi, > > On Mon, 11 Aug 2008, Francis Moreau wrote: > >> I found this in git bisect: >> >> printf >&2 'Are you sure [Y/n]? ' >> case "$(read yesno)" in [Nn]*) exit 1 ;; esac >> >> which looks very weird since read(1) returns a status and not the >> string reads from std input. >> sorry I should have said that there's a status but no output... >> Am I missing something ? > > Yes. "$()" does not return the status, but the output. > But what's the output in that case ? -- Francis ``` ## Reece Dunn, 2008-08-11 15:59 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <3f4fd2640808110859r148550d2h833dae05b9e6544e@mail.gmail.com> URL: https://gitlist.dev/e/3f4fd2640808110859r148550d2h833dae05b9e6544e%40mail.gmail.com In-Reply-To: <38b2ab8a0808110718x2f63608ga3d2d77e317ce4eb@mail.gmail.com> ``` 2008/8/11 Francis Moreau : > Hello > > On Mon, Aug 11, 2008 at 4:15 PM, Johannes Schindelin > wrote: >> Hi, >> >> On Mon, 11 Aug 2008, Francis Moreau wrote: >> >>> I found this in git bisect: >>> >>> printf >&2 'Are you sure [Y/n]? ' >>> case "$(read yesno)" in [Nn]*) exit 1 ;; esac >>> >>> which looks very weird since read(1) returns a status and not the >>> string reads from std input. >>> > > sorry I should have said that there's a status but no output... > >>> Am I missing something ? >> >> Yes. "$()" does not return the status, but the output. >> > > But what's the output in that case ? Using cygwin+bash, I get: $ echo $(read yesno) n $ echo $(read yesno; echo $yesno) n n $ $(read yesno) && echo yes || echo no n yes $ $(read yesno) && echo yes || echo no y yes $ case "$(read yesno)" in [Nn]*) echo "no" ;; esac n $ case "$(read yesno)" in [Nn]*) echo "no" ;; esac y $ case "$(read yesno; echo $yesno)" in [Nn]*) echo "no" ;; esac n no $ case "$(read yesno; echo $yesno)" in [Nn]*) echo "no" ;; esac y So >>> case "$(read yesno)" in [Nn]*) exit 1 ;; esac does not work as expected. Replacing this with case "$(read yesno; echo $yesno)" in [Nn]*) exit 1 ;; esac would work as intended, as Mikael has pointed out. - Reece ``` ## René Scharfe, 2008-08-11 16:18 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <48A06659.6010004@lsrfire.ath.cx> URL: https://gitlist.dev/e/48A06659.6010004%40lsrfire.ath.cx In-Reply-To: <38b2ab8a0808110657y24ac9526wca4acea3bddaec00@mail.gmail.com> ``` Francis Moreau schrieb: > I found this in git bisect: > > printf >&2 'Are you sure [Y/n]? ' > case "$(read yesno)" in [Nn]*) exit 1 ;; esac > > which looks very weird since read(1) returns a status and not the > string reads from std input. Good catch. You need to press Ctrl-C in order to exit, answering "no" means the same as "yes" here -- not very nice. Care to send a patch? Thanks, René ``` ## Francis Moreau, 2008-08-11 16:23 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <38b2ab8a0808110923u21d543f0qbc9dee0f99c97311@mail.gmail.com> URL: https://gitlist.dev/e/38b2ab8a0808110923u21d543f0qbc9dee0f99c97311%40mail.gmail.com In-Reply-To: <3f4fd2640808110859r148550d2h833dae05b9e6544e@mail.gmail.com> ``` On Mon, Aug 11, 2008 at 5:59 PM, Reece Dunn wrote: > $ $(read yesno) && echo yes || echo no > n > yes > $ $(read yesno) && echo yes || echo no > y > yes funny, seeing these 2 cases I'm wondering why Bash is not complaining... -- Francis ``` ## Reece Dunn, 2008-08-11 16:26 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <3f4fd2640808110926w13104a08l687c8accc29e332@mail.gmail.com> URL: https://gitlist.dev/e/3f4fd2640808110926w13104a08l687c8accc29e332%40mail.gmail.com In-Reply-To: <38b2ab8a0808110923u21d543f0qbc9dee0f99c97311@mail.gmail.com> ``` 2008/8/11 Francis Moreau : > On Mon, Aug 11, 2008 at 5:59 PM, Reece Dunn wrote: >> $ $(read yesno) && echo yes || echo no >> n >> yes >> $ $(read yesno) && echo yes || echo no >> y >> yes > > funny, seeing these 2 cases I'm wondering why Bash is not complaining... I don't know; it could be an issue with cygwin. I'll try it on a Linux box later and post the results then for comparison. - Reece ``` ## Francis Moreau, 2008-08-11 16:29 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <38b2ab8a0808110929i47f7e4dt5287d149d10afbaf@mail.gmail.com> URL: https://gitlist.dev/e/38b2ab8a0808110929i47f7e4dt5287d149d10afbaf%40mail.gmail.com In-Reply-To: <3f4fd2640808110926w13104a08l687c8accc29e332@mail.gmail.com> ``` On Mon, Aug 11, 2008 at 6:26 PM, Reece Dunn wrote: > 2008/8/11 Francis Moreau : >> On Mon, Aug 11, 2008 at 5:59 PM, Reece Dunn wrote: >>> $ $(read yesno) && echo yes || echo no >>> n >>> yes >>> $ $(read yesno) && echo yes || echo no >>> y >>> yes >> >> funny, seeing these 2 cases I'm wondering why Bash is not complaining... > > I don't know; it could be an issue with cygwin. > > I'll try it on a Linux box later and post the results then for comparison. > I got the same result on Linux... -- Francis ``` ## Petr Baudis, 2008-08-11 16:49 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <20080811164945.GI32184@machine.or.cz> URL: https://gitlist.dev/e/20080811164945.GI32184%40machine.or.cz In-Reply-To: <3f4fd2640808110859r148550d2h833dae05b9e6544e@mail.gmail.com> ``` On Mon, Aug 11, 2008 at 04:59:32PM +0100, Reece Dunn wrote: > >> On Mon, 11 Aug 2008, Francis Moreau wrote: > >>> case "$(read yesno)" in [Nn]*) exit 1 ;; esac > > does not work as expected. Replacing this with > > case "$(read yesno; echo $yesno)" in [Nn]*) exit 1 ;; esac > > would work as intended, as Mikael has pointed out. Wouldn't it be more elegant to case "$(head -n 1)" in [Nn]*) exit 1 ;; esac Petr "Pasky" Baudis ``` ## René Scharfe, 2008-08-11 17:01 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <48A0705B.3030107@lsrfire.ath.cx> URL: https://gitlist.dev/e/48A0705B.3030107%40lsrfire.ath.cx In-Reply-To: <20080811164945.GI32184@machine.or.cz> ``` Petr Baudis schrieb: > On Mon, Aug 11, 2008 at 04:59:32PM +0100, Reece Dunn wrote: >>>> On Mon, 11 Aug 2008, Francis Moreau wrote: >>>>> case "$(read yesno)" in [Nn]*) exit 1 ;; esac >> does not work as expected. Replacing this with >> >> case "$(read yesno; echo $yesno)" in [Nn]*) exit 1 ;; esac >> >> would work as intended, as Mikael has pointed out. > > Wouldn't it be more elegant to > > case "$(head -n 1)" in [Nn]*) exit 1 ;; esac Only if head is a built-in, otherwise you fork needlessly. Not that this is a performance critical part, but I wouldn't call it "elegant". What's wrong with the following variant, already used a few lines up in the file? read yesno case "$yesno" in [Nn]*) exit 1 ;; esac René ``` ## Petr Baudis, 2008-08-11 17:05 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <20080811170515.GD10151@machine.or.cz> URL: https://gitlist.dev/e/20080811170515.GD10151%40machine.or.cz In-Reply-To: <48A0705B.3030107@lsrfire.ath.cx> ``` On Mon, Aug 11, 2008 at 07:01:15PM +0200, René Scharfe wrote: > Petr Baudis schrieb: > > On Mon, Aug 11, 2008 at 04:59:32PM +0100, Reece Dunn wrote: > >>>> On Mon, 11 Aug 2008, Francis Moreau wrote: > >>>>> case "$(read yesno)" in [Nn]*) exit 1 ;; esac > >> does not work as expected. Replacing this with > >> > >> case "$(read yesno; echo $yesno)" in [Nn]*) exit 1 ;; esac > >> > >> would work as intended, as Mikael has pointed out. > > > > Wouldn't it be more elegant to > > > > case "$(head -n 1)" in [Nn]*) exit 1 ;; esac > > Only if head is a built-in, otherwise you fork needlessly. Not that > this is a performance critical part, but I wouldn't call it "elegant". Ok, exec head -n 1. ;) And yes, I know... I guess I've just spent too much time perl-golfing lately. > What's wrong with the following variant, already used a few lines up in > the file? > > read yesno > case "$yesno" in [Nn]*) exit 1 ;; esac Nothing wrong with this one, of course. -- Petr "Pasky" Baudis The next generation of interesting software will be done on the Macintosh, not the IBM PC. -- Bill Gates ``` ## Francis Moreau, 2008-08-11 17:38 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <38b2ab8a0808111038q686c9581pb277ab6d2229afd@mail.gmail.com> URL: https://gitlist.dev/e/38b2ab8a0808111038q686c9581pb277ab6d2229afd%40mail.gmail.com In-Reply-To: <48A06659.6010004@lsrfire.ath.cx> ``` On Mon, Aug 11, 2008 at 6:18 PM, René Scharfe wrote: > Francis Moreau schrieb: >> I found this in git bisect: >> >> printf >&2 'Are you sure [Y/n]? ' >> case "$(read yesno)" in [Nn]*) exit 1 ;; esac >> >> which looks very weird since read(1) returns a status and not the >> string reads from std input. > > Good catch. You need to press Ctrl-C in order to exit, answering "no" > means the same as "yes" here -- not very nice. Care to send a patch? > done. -- Francis ``` ## Junio C Hamano, 2008-08-11 18:59 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <7v7ianxtqv.fsf@gitster.siamese.dyndns.org> URL: https://gitlist.dev/e/7v7ianxtqv.fsf%40gitster.siamese.dyndns.org In-Reply-To: <48A0705B.3030107@lsrfire.ath.cx> ``` René Scharfe writes: > Petr Baudis schrieb: >> On Mon, Aug 11, 2008 at 04:59:32PM +0100, Reece Dunn wrote: >>>>> On Mon, 11 Aug 2008, Francis Moreau wrote: >>>>>> case "$(read yesno)" in [Nn]*) exit 1 ;; esac >>> does not work as expected. Replacing this with >>> >>> case "$(read yesno; echo $yesno)" in [Nn]*) exit 1 ;; esac >>> >>> would work as intended, as Mikael has pointed out. >> >> Wouldn't it be more elegant to >> >> case "$(head -n 1)" in [Nn]*) exit 1 ;; esac > > Only if head is a built-in, otherwise you fork needlessly. Not that > this is a performance critical part, but I wouldn't call it "elegant". > > What's wrong with the following variant, already used a few lines up in > the file? > > read yesno > case "$yesno" in [Nn]*) exit 1 ;; esac That's the right way to spell it. Sorry, I must have been too tired when I did this. ``` ## Francis Moreau, 2008-08-11 19:47 Subject: Re: git-bisect: weird usage of read(1) Message-ID: <38b2ab8a0808111247w4837a1bfn774b9c2e9b98d38b@mail.gmail.com> URL: https://gitlist.dev/e/38b2ab8a0808111247w4837a1bfn774b9c2e9b98d38b%40mail.gmail.com In-Reply-To: <7v7ianxtqv.fsf@gitster.siamese.dyndns.org> ``` On Mon, Aug 11, 2008 at 8:59 PM, Junio C Hamano wrote: > René Scharfe writes: > >> Petr Baudis schrieb: >>> On Mon, Aug 11, 2008 at 04:59:32PM +0100, Reece Dunn wrote: >>>>>> On Mon, 11 Aug 2008, Francis Moreau wrote: >>>>>>> case "$(read yesno)" in [Nn]*) exit 1 ;; esac >>>> does not work as expected. Replacing this with >>>> >>>> case "$(read yesno; echo $yesno)" in [Nn]*) exit 1 ;; esac >>>> >>>> would work as intended, as Mikael has pointed out. >>> >>> Wouldn't it be more elegant to >>> >>> case "$(head -n 1)" in [Nn]*) exit 1 ;; esac >> >> Only if head is a built-in, otherwise you fork needlessly. Not that >> this is a performance critical part, but I wouldn't call it "elegant". >> >> What's wrong with the following variant, already used a few lines up in >> the file? >> >> read yesno >> case "$yesno" in [Nn]*) exit 1 ;; esac > > That's the right way to spell it. Sorry, I must have been too tired > when I did this. > > > I sent a patch to fix that way already Cheers. -- Francis ```