文件的行编号与sed

Question

我想知道sed是否能够在编号特定行时进行一些行计数工作，假设我有文件

  Some question 
         some answer
         another answer
  Another question
         another answer
         other answer

我想要一个将其转换为：所需输出

的命令

  1_ Some question 
         a_ some answer
         b_ another answer
  2_ Another question
         a_ another answer
         b_ other answer

这可以用 sed 吗？如果没有，如果没有bash编写解决方案脚本怎么办呢？

Answer 1

最好尝试使用awk。我假设您想要编号不以任何空间字符开头的行：

awk '$0 !~ /^[[:blank:]]/ { print ++i "_", $0; next } { print }' infile

它产生：

1_ Some question
         some answer
         another answer
2_ Another question
         another answer
         other answer

Answer 2

Perl有一个方便的功能，++适用于角色：

perl -lpe '
    /^\S/ and do {$inner_counter="a"; s/^/ ++${outer_counter} . "_ "/e}; 
    /^\s/ and s/^\s+/$& . ${inner_counter}++ . "_ "/e
' file

1_ Some question

     a_ some answer

     b_ another answer

2_ Another question

     a_ another answer

     b_ other answer