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#!/bin/sh
# Copyright 2023 Huawei Cloud Computing Technology Co., Ltd.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
set -e
check_var_name() {
local NAME="$1"
if ! expr match "${NAME}" "[A-Z_a-z][0-9A-Z_a-z]*$" >/dev/null; then
echo "expand_exec error: invalid variable name '${NAME}'"
return 1
fi
return 0
}
in_list() {
local NAME="$1"
local VAR_LIST="$2"
check_var_name "${NAME}" && expr match "${NAME}" "\(${VAR_LIST}\)$" >/dev/null
}
EXPANDED_VAR=
expand_var() {
local NAME="$1"
check_var_name "${NAME}" && EXPANDED_VAR="$(eval "printf \"%s\" \"\${$NAME}\"")"
}
PARSED_ARG=
parse_arg() {
local ARG="$1"
local VAR_LIST="$2"
local RESULT=""
local VAR_NAME=""
local PARSE_EXPR=false
local PARSE_VAR_NAME=false
while [ ${#ARG} -gt 0 ]; do
local NEXT="${ARG#?}"
c="${ARG%"${NEXT}"}"
ARG="${NEXT}"
if $PARSE_VAR_NAME; then
# parse <var> from $(<var>)
if [ "$c" = ")" ]; then
# expand var if in cases list
if in_list "${VAR_NAME}" "${VAR_LIST}" && expand_var "${VAR_NAME}"; then
RESULT="${RESULT}${EXPANDED_VAR}"
else
RESULT="${RESULT}\$(${VAR_NAME})"
fi
VAR_NAME=""
PARSE_VAR_NAME=false
else
# accumulate VAR_NAME
VAR_NAME="${VAR_NAME}$c"
if [ ${#ARG} -eq 0 ]; then
# flush unterminated var name
RESULT="${RESULT}\$(${VAR_NAME}"
fi
fi
else
# parse single char
if $PARSE_EXPR; then
if [ "$c" = "(" ]; then
# found "$("
PARSE_VAR_NAME=true
else
RESULT="${RESULT}\$$c"
fi
PARSE_EXPR=false
elif [ "$c" = "$" ]; then
# found "$"
PARSE_EXPR=true
else
# append char
RESULT="${RESULT}$c"
fi
fi
done
PARSED_ARG="'"
while [ ${#RESULT} -gt 0 ]; do
local NEXT="${RESULT#?}"
c="${RESULT%"${NEXT}"}"
RESULT="${NEXT}"
if [ "$c" = "'" ]; then
PARSED_ARG="${PARSED_ARG}'\\''"
else
PARSED_ARG="${PARSED_ARG}$c"
fi
done
PARSED_ARG="${PARSED_ARG}'"
}
# usage: ./expand_exec [VARS...] -- ARGS...
expand_exec() {
local VAR_LIST=""
local VAR_SEP=""
local EXEC_VEC=""
local EXEC_SEP=""
local READ_ARGS=false
while [ "$#" -ge 1 ]; do
local ARG="$1";shift
if $READ_ARGS; then
parse_arg "${ARG}" "${VAR_LIST}"
EXEC_VEC="${EXEC_VEC}${EXEC_SEP}${PARSED_ARG}"
EXEC_SEP=" "
else
if [ "${ARG}" = "--" ]; then
READ_ARGS=true
elif check_var_name "${ARG}"; then
VAR_LIST="${VAR_LIST}${VAR_SEP}${ARG}"
VAR_SEP="\|"
fi
fi
done
exec /bin/sh -c "${EXEC_VEC}"
}
expand_exec "$@"
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