Bash：如果字符串存在，請檢查json響應並寫入文件

Question

我爲json響應蜷縮一個端點並將響應寫入文件。 到目前爲止，我已經得到了一個腳本：

1）。如果該文件不存在，則執行卷曲操作並且2）。否則設置變量

#!/bin/bash 
instance="server1" 
curl=$(curl -sk https://my-app-api.com | python -m json.tool) 
json_response_file="/tmp/file" 

if [ ! -f ${json_response_file} ] ; then 
    ${curl} > ${json_response_file} 
    instance_info=$(cat ${json_response_file}) 
else 
    instance_info=$(cat ${json_response_file}) 
fi 

問題是，該文件可能存在響應錯誤或爲空。 可能使用bash直到，我想

（1）。檢查（使用JQ）curl響應中的字段包含$ instance，然後才寫入該文件。

（2）。重試卷曲XX次，直到響應包含$實例

（3）。寫入文件一旦響應包含$實例

（4）。當上述操作正確完成時，設置變量instance_info = $（cat $ {json_response_file}）。

我開始喜歡這個......然後就死......

until [[ $(/usr/bin/jq --raw-output '.server' <<< ${curl}) = $instance ]] 
do 

Answer 1

一個理智的實現可能是這個樣子：

retries=10 
instance=server1 
response_file=filename 

# define a function, since you want to run this code multiple times 
# the old version only ran curl once and reused that result 
fetch() { curl -sk https://my-app-api.com; } 

instance_info= 
for ((retries_left=retries; retries_left > 0; retries_left--)); do 
    content=$(fetch) 
    server=$(jq --raw-output '.server' <<<"$content") 
    if [[ $server = "$instance" ]]; then 
    # Writing isn't atomic, but renaming is; doing it this way makes sure that no 
    # incomplete response will ever exist in response_file. If working in a directory 
    # like /tmp where others users may have write, use $(mktemp) to create a tempfile with 
    # a random name to avoid security risk. 
    printf '%s\n' "$content" >"$response_file.tmp" \ 
     && mv "$response_file.tmp" "$response_file" 
    instance_info=$content 
    break 
    fi 
done 
[[ $instance_info ]] || { echo "ERROR: Giving up after $retries retries" >&2; }