Configration in script（uci 脚本使用bug，以及API分析）

BUG: config_load之后，调用uci delete或者uci set xxx.xxx.xxx=''，再度掉用config_load，之后通过config_get读取出来的值将会出错,delete之后不使用commit

解决方法1：使用API函数config_unset或者config_set

解决方法2：

config_clear() {

local SECTION="$1"

#遍历每一项option,并将其unset

for oldvar in `set | grep ^CONFIG_${SECTION:+${SECTION}_} | \

sed -e 's/\(.*\)=.*$/\1/'` ; do

unset $oldvar

done

}

config () {

local cfgtype="$1"

local name="$2"

config_clear $name

export ${NO_EXPORT:+-n} CONFIG_NUM_SECTIONS=$(($CONFIG_NUM_SECTIONS + 1))

name="${name:-cfg$CONFIG_NUM_SECTIONS}"

append CONFIG_SECTIONS "$name"

[ -n "$NO_CALLBACK" ] || config_cb "$cfgtype" "$name"

export ${NO_EXPORT:+-n} CONFIG_SECTION="$name"

export ${NO_EXPORT:+-n} "CONFIG_${CONFIG_SECTION}_TYPE=$cfgtype"

}

在调用api时，首先我们需要调用config_load

config_load() {

[ -n "$IPKG_INSTROOT" ] && return 0

uci_load "$@"

}
uci_load() {

local PACKAGE="$1"

local DATA

local RET

local VAR

_C=0

if [ -z "$CONFIG_APPEND" ]; then

for VAR in $CONFIG_LIST_STATE; do

export ${NO_EXPORT:+-n} CONFIG_${VAR}=

export ${NO_EXPORT:+-n} CONFIG_${VAR}_LENGTH=

done

export ${NO_EXPORT:+-n} CONFIG_LIST_STATE=

export ${NO_EXPORT:+-n} CONFIG_SECTIONS=

export ${NO_EXPORT:+-n} CONFIG_NUM_SECTIONS=0

export ${NO_EXPORT:+-n} CONFIG_SECTION=

fi

DATA="$(/sbin/uci ${UCI_CONFIG_DIR:+-c $UCI_CONFIG_DIR} ${LOAD_STATE:+-P /var/state} -S -n export "$PACKAGE" 2>/dev/null)"

RET="$?"

[ "$RET" != 0 -o -z "$DATA" ] || eval "$DATA"

unset DATA

${CONFIG_SECTION:+config_cb}

return "$RET"

}

1、首先通过uci export $PACKAGE 获取配置文件的内容（其他参数就不一一简绍了，具体查看uci --help）

package xxx

config xxx xxx

option xxx xxx

list      xxx  xxx

2、之后eval "$DATA"，将package config option替换成函数（这一步是很让我很惊艳的用法，得向大牛学习）

package() {

return 0

}
config () {

local cfgtype="$1"

local name="$2"

export ${NO_EXPORT:+-n} CONFIG_NUM_SECTIONS=$(($CONFIG_NUM_SECTIONS + 1))

name="${name:-cfg$CONFIG_NUM_SECTIONS}"

append CONFIG_SECTIONS "$name"

[ -n "$NO_CALLBACK" ] || config_cb "$cfgtype" "$name"

export ${NO_EXPORT:+-n} CONFIG_SECTION="$name"

export ${NO_EXPORT:+-n} "CONFIG_${CONFIG_SECTION}_TYPE=$cfgtype"

}
option () {

local varname="$1"; shift

local value="$*"

export ${NO_EXPORT:+-n} "CONFIG_${CONFIG_SECTION}_${varname}=$value"

[ -n "$NO_CALLBACK" ] || option_cb "$varname" "$*"

}
list() {

local varname="$1"; shift

local value="$*"

local len

config_get len "$CONFIG_SECTION" "${varname}_LENGTH" 0

[ $len = 0 ] && append CONFIG_LIST_STATE "${CONFIG_SECTION}_${varname}"

len=$(($len + 1))

config_set "$CONFIG_SECTION" "${varname}_ITEM$len" "$value"

config_set "$CONFIG_SECTION" "${varname}_LENGTH" "$len"

append "CONFIG_${CONFIG_SECTION}_${varname}" "$value" "$LIST_SEP"

list_cb "$varname" "$*"

}

3、通过这四个函数将每一项配置项设置到环境变量当中

（bug出现原因：当设入环境变量后，通过uci delete或uci set 删除只会操作换存，在调用config_load 因为option项不存在了，则不会在度设置到环境变量中，因此还是删除之前的值，而不是空）

4、之后的config_get之类的函数就是获取环境变量的值

for oldvar in `set | grep ^CONFIG_${SECTION:+${SECTION}_} | \

sed -e 's/\(.*\)=.*$/\1/'` ; do


for oldvar in `set | grep ^CONFIG_${SECTION:+${SECTION}_} | \

sed -e 's/\(.*\)=.*$/\1/'` ; do


for oldvar in `set | grep ^CONFIG_${SECTION:+${SECTION}_} | \

sed -e 's/\(.*\)=.*$/\1/'` ; do

for oldvar in `set | grep ^CONFIG_${SECTION:+${SECTION}_} | \

sed -e 's/\(.*\)=.*$/\1/'` ; do

for oldvar in `set | grep ^CONFIG_${SECTION:+${SECTION}_} | \

sed -e 's/\(.*\)=.*$/\1/'` ; do

for oldvar in `set | grep ^CONFIG_${SECTION:+${SECTION}_} | \

sed -e 's/\(.*\)=.*$/\1/'` ; do