On 3 August 2010 22:55, Eric Blake <ebl...@redhat.com> wrote: > [adding autoconf to document some shell bugs] > > On 08/03/2010 02:32 PM, Ralf Wildenhues wrote: >> Interesting shell unportability: >> >> $ bash -c 'f=" val" e=; echo "$e"$f' >> val >> $ ksh -c 'f=" val" e=; echo "$e"$f' >> val >> >> ksh93, dash, zsh all do it like ksh. Is that a bug in bash? > > Yes; adding bug-bash accordingly. According to POSIX: > > http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_05 > > "After parameter expansion ( Parameter Expansion ), command substitution > ( Command Substitution ), and arithmetic expansion ( Arithmetic > Expansion ), the shell shall scan the results of expansions and > substitutions that did not occur in double-quotes for field splitting > and multiple fields can result." > > Since $f is not quoted, its expansion must undergo field splitting. But > since "$e" is quoted, it must not be elided even though empty. The > result must be _two_ fields, as if you had done "echo '' 'val'". > > But it is _also_ a bug in zsh; adding zsh-workers accordingly. > > $ zsh -cvx 'f=" val" e=; echo "$e"$f' > +zsh:1> f=' val' e='' > +zsh:1> echo ' val' > val > > Oops - zsh only passed one argument to echo, with a leading space, > instead of passing an empty argument and letting echo supply the space. > ksh93, pdksh, and dash get it right (although dash doesn't use quotes > in -vx output, hence my use of n() to force things to tell; n() is > another way to expose the bash and zsh bugs).
zsh doesn't do word splitting by default, you can enable it with the = modifier: % zsh -fcvx 'f=" val" e=; echo "$e"$=f' +zsh:1> f=' val' e='' +zsh:1> echo '' val val does what you want Alternatively you can make zsh try to be closer to sh by setting argv[0] to sh when executing it, or running 'emulate sh' as the first command (and possibly other ways I don't know about): % zsh -fcvx 'emulate sh;f=" val" e=; echo "$e"$f' +zsh:1> emulate sh +zsh:1> f=' val' e='' +zsh:1> echo '' val val There's also --shwordsplit for this specific case: % zsh --shwordsplit -fcvx 'f=" val" e=; echo "$e"$f' +zsh:1> f=' val' e='' +zsh:1> echo '' val val (the -f above only avoids loading my .zshenv which would spam my output) -- Mikael Magnusson
