On Wed, Mar 24, 2010 at 12:43 AM, Rob Robason <r...@robason.net> wrote:
> Configuration:
> OS: Fedora 11 - with all updates applied
> Bash: version 4.0.23(1)-release
>
> Problem description:
> When stdin is a pipeline to 'mapfile', 'readarray', and 'read -a' shell
> built-in commands, they fail to assign any values to the target array.
> The array is neither unset nor altered in any way. No error message is
> produced, and $? == 0.
> None of the available options have any effect on this behavior.
> Oddly, when input is provided via keyboard or redirection (<), these
> commands function properly. This last point seems really weird to me and
> points to the built-ins' or shell's internal handling of a pipeline.
>
> mapfile/readarray example (mapfile behaves identically to readarray):
> $ ls -a | readarray # using the default MAPFILE array
> $ echo $?
> 0
> $ echo "${#mapfi...@]}"
> 0
> $
>
> Other forms of mapfile/readarray that fail:
> $ ls -a | readarray -u0 # specified input file descriptor
> $ echo "${#mapfi...@]}"
> 0
> $
>
> $ declare -a myArray # (optional) Declaring myArray has no
> effect
> $ ls -a | readarray myArray
> $ echo "${#myarr...@]}"
> 0
> $
> a
It's a faq, commands in a pipe are executed in a subshell and don't modify
the parent shell.
