# ------------------- function --------------------
# 函数：抓取（过滤）出json指定字段值
# 入参1：json
# 入参2：过滤条件，支持“.”，“.[]”，“.fieldName”，“.[index]”，及其组合
# 入参3：是否需要检查json合法性，0：不需要；其它：需要
# 入参4：缩进量，格式化时用到
fetch() {JSON=$1FILTER=$2NEED_CHECK=$3FORMATTED_JSON=# 检查json是否合法if [ "0" != "$NEED_CHECK" ]; thenFORMATTED_JSON=`format "$JSON" "$4"`elseFORMATTED_JSON=$JSONfi# 读取上一条命令return的执行状态，非0表示异常if [ $? != 0 ]; thenecho "Error [line:$LINENO]: invalid json"return 1fi# .直接返回全部jsonif [ "." = "$FILTER" ]; thenecho "$FORMATTED_JSON"return 0fi# 将复合过滤条件以.号拆分成单个的过滤条件数组# 所有的.号替换成空格，加上（）即可自动变成数组FILTER_ARRAY=(${FILTER//./ })# 遍历所有单个的过滤条件for(( i=0; i<${#FILTER_ARRAY[*]}; i++ ))doCURRENT_FILTER=${FILTER_ARRAY[$i]}# []的情况# 对数组的各个元素递归if [  "[]" = "$CURRENT_FILTER" ]; then# 检查json是否为数组if [ "[" != "${FORMATTED_JSON:0:1}" ]; thenecho "Error [line:$LINENO]: not an array"return 1fiCHILD_JSON_ARRAY=`getChildrenJson "$FORMATTED_JSON"`# 后续的过滤条件REMAINING_FILTER=for(( j=`expr $i + 1`; j<${#FILTER_ARRAY[*]}; j++ ))doREMAINING_FILTER="${REMAINING_FILTER}.${FILTER_ARRAY[$j]}"done# 对每个 child 传入后续的过滤条件递归RESULT="["for CHILD in ${CHILD_JSON_ARRAY[*]}do# 递归调用RESULT="${RESULT}`fetch "$CHILD" "$REMAINING_FILTER" 0`,"done# 去掉最后一个“,”加上“]”# “%,*”表示从右侧开始，去掉最后一个“,”及右边的字符RESULT="${RESULT%,*}]"# 后续过滤条件已经做完，直接返回echo "$RESULT"return 0# [0],[1]...的情况# 似乎没有[0-9]+的写法，用[[0-9][0-9]*代替elif [ `echo "$CURRENT_FILTER" | grep "^[[0-9][0-9]*]$"` ]; then# 读取指定的数组元素# “#[”删除最左边的[INDEX=${CURRENT_FILTER#[}INDEX=${INDEX%]}FORMATTED_JSON=`getChildrenJson "$FORMATTED_JSON" "$INDEX"`# 其它都当做读取字段处理elseFORMATTED_JSON=`getFieldValue "$FORMATTED_JSON" "$CURRENT_FILTER"`fidoneecho "$FORMATTED_JSON"return 0
}# 函数：获取数组json的所有子json，或指定位置的子json
# 入参1：json，必须是数组
# 入参2：index，指定想要的子json的位置，从0开始，不指定则获取全部
# 出参：json数组
getChildrenJson() {JSON=$1INDEX=$2RESULT_JSON_ARRAY=()# []{}块，每关闭一个{}块，即为一个子json，根[块关闭之后则为扫描结束BLOCK_ARRAY=('[')CURRENT=CHILD_JSON=# 从1开始，因为第0位的[已经记录到BLOCK_ARRAY里面去了JSON_LENGTH=${#JSON}POSITION=1while (( ${POSITION}<${JSON_LENGTH} ))doCURRENT=${JSON:POSITION:1}CHILD_JSON="${CHILD_JSON}${CURRENT}"LAST_BLOCK_INDEX=`expr ${#BLOCK_ARRAY[*]} - 1`CURRENT_BLOCK=${BLOCK_ARRAY[$LAST_BLOCK_INDEX]}if [ """ = "$CURRENT_BLOCK" ]; thenif [ """ = "$CURRENT" ]; thenunset BLOCK_ARRAY[$LAST_BLOCK_INDEX]if [ ${#BLOCK_ARRAY[*]} == 1 ]; then# 如果指定了index参数，并且此处恰好就是，则返回当前 childif [ "${#RESULT_JSON_ARRAY[*]}" = "$INDEX" ]; thenecho "$CHILD_JSON"return 0fi# child 添加到数组RESULT_JSON_ARRAY[${#RESULT_JSON_ARRAY[*]}]="$CHILD_JSON"# 清空 childCHILD_JSON=# 如果下一个字符是逗号，跳过NEXT_POSITION=`expr $POSITION + 1`if [ "," = "${JSON:NEXT_POSITION:1}" ]; thenlet POSITION++fififilet POSITION++continuefiif [ "{" = "$CURRENT" ]; then# 记录一个{}块BLOCK_ARRAY[${#BLOCK_ARRAY[*]}]='{'elif [ "}" = "$CURRENT" ]; then# 关闭一个{}块unset BLOCK_ARRAY[`expr ${#BLOCK_ARRAY[*]} - 1`]# 退出到了根[]块，表示一个child已经结束if [ ${#BLOCK_ARRAY[*]} == 1 ]; then# 如果指定了index参数，并且此处恰好就是，则返回当前 childif [ "${#RESULT_JSON_ARRAY[*]}" = "$INDEX" ]; thenecho "$CHILD_JSON"return 0fi# child 添加到数组RESULT_JSON_ARRAY[${#RESULT_JSON_ARRAY[*]}]="$CHILD_JSON" # 清空 childCHILD_JSON=# 如果下一个字符是逗号，跳过NEXT_POSITION=`expr $POSITION + 1`if [ "," = "${JSON:NEXT_POSITION:1}" ]; thenlet POSITION++fi                fielif [ """ = "$CURRENT" ]; thenBLOCK_ARRAY[${#BLOCK_ARRAY[*]}]="""elif [ "," = "$CURRENT" ]; then# 当前在根[]块，表示一个child已经结束if [ ${#BLOCK_ARRAY[*]} == 1 ]; then# 删除已经添加进去的逗号CHILD_JSON="${CHILD_JSON%,}"# 如果指定了index参数，并且此处恰好就是，则返回当前 childif [ "${#RESULT_JSON_ARRAY[*]}" = "$INDEX" ]; thenecho "$CHILD_JSON"return 0fi# child 添加到数组RESULT_JSON_ARRAY[${#RESULT_JSON_ARRAY[*]}]="$CHILD_JSON"# 清空 childCHILD_JSON=fifilet POSITION++done# 走到这里说明没有传 index，或 index 越界if [ "$INDEX" ]; thenecho "Error [line:$LINENO]: array out of bounds"exit 1fiecho "${RESULT_JSON_ARRAY[*]}"return 0
}# 函数：获取指定字段名称的值，默认json中同一层次不存在相同的字段名称
# 入参1：json
# 入参2：字段名称
# 出参：指定字段名称的值
getFieldValue() {JSON=$1FIELD=$2VALUE=POSITION=0LENGTH=${#JSON}FIELD_LENGTH=${#FIELD}# 字段名称长度 + "": 的长度3个字符MATCH_LENGTH=`expr $FIELD_LENGTH + 3`while(( $POSITION<$LENGTH ))doMATCH_STR=${JSON:POSITION:MATCH_LENGTH}# 匹配到了if [ "$MATCH_STR" = ""$FIELD":" ]; thenPOSITION=`expr $POSITION + $MATCH_LENGTH`# 向后读取 valueBLOCK_ARRAY=()CURRENT=${JSON:POSITION:1}# 如果 value 的第一位不是{,[,"的任何一个，则直接开始读取，读到，或}结束if [[ "{" != "$CURRENT" && "[" != "$CURRENT" && """ != "$CURRENT" ]]; thenVALUE="$CURRENT"let POSITION++while(( $POSITION<$LENGTH  ))doCURRENT=${JSON:POSITION:1}if [[ "," = "$CURRENT" || "}" = "$CURRENT" ]]; thenecho "$VALUE"return 0elseVALUE="${VALUE}${CURRENT}"filet POSITION++doneecho "Error [line:$LINENO]: unknown error, maybe bug"return 1fi# 读取第一个{,[,或"，直到退出为止BLOCK_ARRAY[0]="$CURRENT"VALUE="$CURRENT"let POSITION++while(( ${#BLOCK_ARRAY[*]} != 0 ))doCURRENT=${JSON:POSITION:1}VALUE="${VALUE}${CURRENT}"if [[ "}" = "$CURRENT" || "]" = "$CURRENT" ]]; thenunset BLOCK_ARRAY[`expr ${#BLOCK_ARRAY[*]} - 1`]elif [[ "{" = "$CURRENT" || "[" = "$CURRENT" ]]; thenBLOCK_ARRAY[${#BLOCK_ARRAY[*]}]="$CURRENT"elif [ """ = "$CURRENT" ]; thenLAST_BLOCK_INDEX=`expr ${#BLOCK_ARRAY[*]} - 1`CURRENT_BLOCK=${BLOCK_ARRAY[$LAST_BLOCK_INDEX]}if [ """ = "$CURRENT_BLOCK" ]; thenunset BLOCK_ARRAY[$LAST_BLOCK_INDEX]elseBLOCK_ARRAY[${#BLOCK_ARRAY[*]}]="""fifilet POSITION++if [ $POSITION -ge $LENGTH ]; thenbreakfidoneecho "$VALUE"return 0filet POSITION++doneecho "Error [line:$LINENO]: not found field $FIELD"return 1
}# 函数：去掉所有空白字符
# 入参1：字符串
# 出参：去掉所有空白字符的字符串
clearBlank() {STR=$1RESULT=POSITION=0LENGTH=${#STR}while(( $POSITION<$LENGTH ))doCURRENT=${STR:POSITION:1}if [ $CURRENT ]; thenRESULT="${RESULT}${CURRENT}"filet POSITION++doneecho "$RESULT"return 0
}

# --------------------- main ----------------------
# 读取主流程参数
# 入参1：json
# 入参2：缩进字符数，默认为2
# 入参3：字段过滤器
echo -e `fatch "$1" "$3" "1" "$2"`
# --------------------- main ----------------------

pj '{"a":"b"}' 4 ".a"

# ------------------- function --------------------
# 函数：打印命令提示
help() {echo "$0 [-i INDENT] [-f FILTER] [-d JSON] [-c]Format json and fetch field value.
OPTIONS:-i      indent, 2 characters as default-f      filter, e.g. .fieldName1.[0].fieldName2.[].fieldName3-d      data, json-c      check if json is valid
" >&2exit 1
}
# ------------------- function --------------------

# --------------------- main ----------------------
# 入参
JSON=
INDENT=
FILTER=
CHECK=# 读取命令行参数
# 冒号表示该参数需要传值，如此处 -i -f -d 参数
while getopts "i:f:d:c" opt; do# 参数在 opt 变量里面case $opt ini)# 参数后的值存放在 OPTARG 变量中INDENT=$OPTARG;;f)FILTER=$OPTARG;;d)JSON=$OPTARG;;c)CHECK=1;;?)help;;esac
doneif [ ! "$JSON" ]; thenecho "Error: json missing"exit 1
fi
if [ ! "$INDENT" ]; thenINDENT=2
fi
if [ ! "$FILTER" ]; thenFILTER="."
fi# 对于确定 json 一定是正确的格式的情况下，检查就有点多余
# 只有传了 -c 参数，才检查json是否合法
if [ $CHECK ]; thenCHECK_RESULT=`format "$JSON"`if [ $? != 0 ]; thenecho "Error [line:$LINENO]: invalid json"exit 1fi
fi
# 清除所有空白字符，否则目前的逻辑可能会对字段抓取的准确性造成一定影响
JSON=`clearBlank "$JSON"`
# 抓取字段
MAIN_RESULT=`fetch "$JSON" "$FILTER" "0" "$INDENT"`
# 尝试格式化
FORMATTED_MAIN_RESULT=`format "$MAIN_RESULT" "$INDENT"`
# 如果抓取的字段已经不是 json，格式化会失败，则返回非格式化的字段
if [ $? == 0 ]; thenecho -e "$FORMATTED_MAIN_RESULT"
elseecho -e "$MAIN_RESULT"
fi
# --------------------- main ----------------------

pj -d '{"a":"b"}' -i 4 -f .a -c

pj -d '{"a":"b"}' -f .a