Date: Mon, 14 Mar 2011 18:10:28 -0430 From: Andres Perera <andres.p@zoho.com> To: Maxim Khitrov <max@mxcrypt.com> Cc: Devin Teske <dteske@vicor.com>, FreeBSD <freebsd-questions@freebsd.org> Subject: Re: Shell script termination with exit function in backquotes Message-ID: <AANLkTim0GvnAyK3%2B=Bd1Sr=maz0B3Ybgve_c6FKWwfNs@mail.gmail.com> In-Reply-To: <AANLkTimrnV2rJLyc3M4e3gGy_GUDLXp128f6n8svM3_g@mail.gmail.com> References: <AANLkTi=-CFmxRicGcosvzhBbM3DMjbWwQNirMrJ1_KP=@mail.gmail.com> <759A467E-407A-4DB8-9756-08011B5405F0@vicor.com> <AANLkTi=CXLFUBhnY1LuhkeUiGHHGZ43yd%2BMYE9L50_O4@mail.gmail.com> <AANLkTimrnV2rJLyc3M4e3gGy_GUDLXp128f6n8svM3_g@mail.gmail.com>
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On Mon, Mar 14, 2011 at 7:46 AM, Maxim Khitrov <max@mxcrypt.com> wrote: > On Mon, Mar 14, 2011 at 3:16 AM, Andres Perera <andres.p@zoho.com> wrote: >> On Sun, Mar 13, 2011 at 9:49 PM, Devin Teske <dteske@vicor.com> wrote: >>> If you make the changes that I've suggested, you'll have consistent exe= cution. The reason you're having inconsistent behavior is because Linux has= /bin/sh symbolically linked to /bin/bash while FreeBSD has a more traditio= nal shell (we'll call it bourne shell "plus"). >> >> that is misleading because command substitutions have traditionally >> invoked subshells, and freebsd sh(1)/ash is an exception, not the norm >> >> in this case, ksh and bash deviates are clearly closer to standard >> bourne behaviour >> > > Thanks for that explanation. I can understand the benefits of > optimizing away subshell execution, but that can clearly lead to > unexpected behavior. Is there some documentation on when this > optimization is utilized (i.e. the command executed without a > subshell)? Would I be correct in assuming that it is only restricted > to built-in commands that are known not to produce any output, such as > 'exit'? i would check the source, autoconf docs, and http://www.in-ulm.de/~mascheck= / netbsd has been patched to fix `exit 1`, according to the last site > > - Max >
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