bash/sed - 在文件的特定位置添加多行

Question

我想自动将新后端添加到配置文件中，但不知道该怎么做。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来添加另一个具有特定 url 和密码的后端条目。

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

同时将名称“backend-3”附加到“[backend]”部分的“backends =”行。

有没有办法通过一般的 sed 或 bash 脚本来完成这项工作？

感谢任何帮助或提示！

Answer 1

awk 用于任意新后端条目，newbackendname、url 和 secret 是唯一提供的输入。只需将新后端添加到backends =-list 和一般[backend]-block 之后的相应块。

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 cmets 可以让您轻松理解。使用此代码，您也可以通过 shell 变量将 url 和 secret 添加为 awk -vurl="$URL" -vsecret="$SECRET" -vnewentry="$NEWBACKEND" '...' infile.txt

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，您可能希望使用双引号来扩展变量。例如;

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

Answer 3

您可以尝试使用awk 的方法。它向以 backends 开头的行添加 backends 条目，并在 [backend][backend-x] 部分/strong> 块（在 connectionsperhost 之后）。
显然它依赖于后端的条目是否正确，因为它不单独计算 [backend] 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