get_dracut_drivers

#! /bin/bash
# This code reads a list of modules from stdin, and takes the
# content of the dracut configuration files as argv[1].
# It evaluates the dracut configuration to set the module-related
# configuration variables add_drivers etc.
# It appends the gathered module names to the input, and
# filters the result using the regex from the omit_drivers variable.
# The code is meant to be executed with decreased privileges,
# in order to avoid sourcing arbitrary scripts as root.

[[ "${WM2_VERBOSE:-0}" -le 2 ]] || set -x

ME=${0##*/}
add_drivers=""
force_drivers=""
omit_drivers=""
drivers=""

eval "$1" ||
    echo "$0: error evaluating dracut configuration" >&2

# sanitize omit_drivers; code similar to dracut.sh 059
# filter out empty lines; also handle the case where omit_drivers is empty
omit_drivers_corrected="^[[:space:]]*$"
for d in $omit_drivers; do
	[[ " $drivers $add_drivers " == *\ $d\ * ]] && continue
	[[ " $drivers $force_drivers " == *\ $d\ * ]] && continue
	omit_drivers_corrected+="|$d"
done

if [[ "${WM2_VERBOSE:-0}" -gt 0 ]]; then
    echo "$ME: drivers='$drivers'" >&2
    echo "$ME: add_drivers='$add_drivers'" >&2
    echo "$ME: force_drivers='$force_drivers'" >&2
    echo "$ME: omit_drivers='$omit_drivers'" >&2
    echo "$ME: omit_drivers_corrected='$omit_drivers_corrected'" >&2
fi

# The sed command below converts space-separated lists to newline-separated
{
    cat
    echo $drivers $add_drivers $force_drivers
} |
    sed -E 's/[[:space:]]+/\n/g;s/\n*$//' |
    grep -Ev "$omit_drivers_corrected"