bash/sed -在文件中的特定位置添加多行

Question

我想自动向配置文件中添加新的后端，但不知道如何做到这一点。文件的相关部分如下所示：

[backend]
backends = backend-1 backend-2
timeout = 10
connectionsperhost = 100

[backend-1]
url = https://somedomain.com
secret = 6135bcb7849ca1886e2de193

[backend-2]
url = https://anotherdomain.com
secret = 75048ad646a5af787cbbaaa3 

我正在寻找一个简单的解决方案，以添加另一个带有特定网址和秘密的后端条目。

[backend-3]
url = https://adiffrentdomain.com
secret = 42349234238423424

同时，将“后端-3”的名称附加到“后端”部分的“后端=”行中。

是否有一种方法可以使这个工作与sed或bash脚本通用？

谢谢您的帮助或提示！

Answer 1

您可以使用awk尝试一种方法。它将一个后端条目添加到以后端开始的行中，并在后端块的最后一行之后(在connectionsperhost之后)附加一个带有给定信息的后端-x部分。

显然，它依赖于后端的条目是正确的，因为它不单独计算后端部分。

url="www.domain.com"
s=9283283h4923h42934

% awk -v url="${url}" -v s="${s}" '/^backends/{x=NF-1; $0=$0" backend-"x} 
    /^connectionsperhost/{ print; $0="\n[backend-"x"]\nurl = "url"\nsecret = "s} 
    {print}' file
[backend]
backends = backend-1 backend-2 backend-3
timeout = 10
connectionsperhost = 100

[backend-3]
url = www.domain.com
secret = 9283283h4923h42934

[backend-1]
url = https://somedomain.com
secret = 6135bcb7849ca1886e2de193

[backend-2]
url = https://anotherdomain.com
secret = 75048ad646a5af787cbbaaa3

数据

cat file
[backend]
backends = backend-1 backend-2
timeout = 10
connectionsperhost = 100

[backend-1]
url = https://somedomain.com
secret = 6135bcb7849ca1886e2de193

[backend-2]
url = https://anotherdomain.com
secret = 75048ad646a5af787cbbaaa3 

Answer 2

使用sed

$ sed '/backends =/s/$/ backend-3/;/^\[backend-2/{N;N;s|secret.*|&\n\n[backend-3] \
url = https://adifferentdomain.com \
secret = 42349234238423424|}' input_file
[backend]
backends = backend-1 backend-2 backend-3
timeout = 10
connectionsperhost = 100

[backend-1]
url = https://somedomain.com
secret = 6135bcb7849ca1886e2de193

[backend-2]
url = https://anotherdomain.com
secret = 75048ad646a5af787cbbaaa3

[backend-3]
url = https://adiffrentdomain.com
secret = 42349234238423424

如果输入来自变量，则需要使用双引号来展开变量。例如；

sed "/backends =/s/$/ backend-3/;$a\\n[backend-3] \
url = $url_input \
secret = $secret_input" input_file

Answer 3

将awk用于任意的新后端条目，其中newbackendname、url和secret是唯一提供的输入。只需将新的后端添加到backends =-list和相应的块中，直接在通用[backend]-block之后。

awk -vnewentry="newbackendname" -vurl="http://new.url" -vsecret="secret123" '
  #in backends= line: add new entry (at first position)
  #and set `add` marker
  /^backends =/{sub(/^backends = /,"&"newentry" ",$0) ; add=1}
  #marker exists and empty line (end of header block) is found:
  #print new entry and unset marker `add`
  add && /^$/{ print "\n["newentry"]"
               print "url = "url
               print "secret = "secret
               add=0}
  #print by default
  1' infile.txt

希望这些评论能使我们更容易理解。使用这段代码，您可以通过shell变量添加url和awk -vurl="$URL" -vsecret="$SECRET" -vnewentry="$NEWBACKEND" '...' infile.txt。