Re: Splitting string to array removes pipe symbol

[Peter Stephenson <pws@csr.com>]

Vincent Stemen wrote:
> However, when the globsubst option is set, it removes the pipe '|'
> symbol when it does the split.  Here is the trace output.
> 
>   +./t:62> cmd=uncompress foobar | cpio -i --quiet --unconditional
>   +./t:63> cmd=( uncompress foobar cpio -i --quiet --unconditional )

You have null_glob (or maybe csh_null_glob) set.  `|' is split to a
single bar.  Evaluation of the words takes place as if all the elements
of the array are arguments, which is different from evaluating as a
command.  (This is inevitable --- the only way of doing it differently
would be to parse the line again completely from scratch after the
glob_subst.)  In this case, the `|' is treated the same as (|),
i.e. either nothing or nothing, and removed since nothing matches it.
(You'd normally need the parentheses to stop it being evaluated as a
pipe, but it can't be in an argument list.)

You can fix this particular problem by quoting,
  cmd=("${(@)=cmd}")
but only because that cancels the effect of glob_subst, so that `|' is
just an ordinary character.  This may not be what you want.  It's
likely to be very difficult to force the shell both to split a line into
words *and* to parse it again as a full command line without joining it
up again.

Most people would probably come up with something using `eval'.  What you
should do depends why you need to split it at all.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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