Dealing with arrays in bash

arrays.sh

#!/bin/bash

# this is *complicated*
#
# we want to be able to set an array to the value of another
# array. this is harder than it should be
#
# The call:
#   _set_array foo 1 "2 3" "4 5 6"
# should execute:
#   foo=(1 "2 3" "4 5 6")
#
# the only way to get 'foo' on the LHS of the assignment is within an
# eval, but at that point we need to escape the rest of the parameters
# to avoid losing information
#
# 'declare -p foo' prints a properly-escaped expression that, when
# eval-ed, will assign to foo its current value
#
# so:
function _set_array() {
    # take the name of teh destination array
    local _sa_varname="$1"
    shift
    # copy the rest of the arguments to a local array we can call by
    # name ("declare -p @" doesn't work, $@ is magical)
    local -a _private_name_=("$@")
    # get the declare string
    local _sa_assignment="$(declare -p _private_name_)"
    # remove the parts we don't want
    _sa_assignment="${_sa_assignment#declare -a _private_name_=\'}"
    _sa_assignment="${_sa_assignment%\'}"
    # put in the assignment to the destination array
    _sa_assignment="$_sa_varname=$_sa_assignment"
    # eval the whole thing
    eval "$_sa_assignment"
}
# there may be a simpler way, but I couldn't find it


# example of function that "returns" an array:
#  find_files_in_array $name_of_array $option_to_find $more_option_to_find
function find_files_in_array() {
    # get the name of the destination array
    local _ffia_varname="$1"
    shift # and remove it from $@

    # local variables: I prefix their names because they may conflict
    # with the name of the destination array, in which case the 'eval'
    # is _set_array will assign to the *local* variablems :(((
    local -a _ffia_files
    local _ffia_file

    # "simple" read from stdin and accumulate in array; we can't use a
    # pipe, because in that case the 'while' would run in a separate
    # process, and we'd lose its variables
    while read -r -d $'\0' _ffia_file; do
        _ffia_files+=("$_ffia_file")
    done < <(find . -type f "$@" -print0)

    # finally, assign the result to the destination array
    _set_array "$_ffia_varname" "${_ffia_files[@]}"
}

# and here is how to use it
function print_files() {
    # declare a variable
    local -a files
    # fill it with file names
    find_files_in_array files -name 'foo*'

    # print each file name
    local f
    for f in "${files[@]}"; do
        echo "> $f"
    done
}

print_files