在bash中多行匹配后附加一个字符串 [英] Append a string after a multiple line match in bash

问题描述

在bash中多行匹配后，我需要一个sed或awk命令来打印一行.例如，将该文件作为输入:

I would need a sed or awk command to print a line after a multiple line match in bash. For example having this file as input:

admin:
  users:
    - user1
    - user2

read_only:
  users:
    - user3

write_only:
  users:
    - user4

access_only:
  users:
    - user5
    - user6

..我需要将其作为输出:

..I would need to have this as output:

admin:
  users:
    NEW USER
    - user1
    - user2

read_only:
  users:
    - user3

write_only:
  users:
    - user4

access_only:
  users:
    - user5
    - user6

正则表达式应与前两行admin: users:匹配，然后附加NEW USER行.

The regex should match the first two lines admin: users: and then append NEW USER line.

如何执行此操作?我应该使用sed还是awk?如何? 谢谢

How to do this? Should I use sed or awk? How? Thank you

推荐答案

使用sed

在/^[a-z_]\+:/和/^$/之间定界块，因此您可以在一个块中进行Somme处理:

With sed

Delimit block between /^[a-z_]\+:/ and /^$/, so you could do somme process in one block:

sed -e $'/^admin:/,/^$/{/users:/a\    NewUser\n}'

可以这样写:

NEWUSER="user2017"
sed -e "/^admin:/,/^$/{
    /users:/a\    - $NEWUSER
}"

(通过使用双引号，我可以使用命令行或脚本中的变量)

(By using double quotes, I could use variable from commandline or script)

这将呈现:

admin:
  users:
    - user2017
    - user1
    - user2

read_only:
  users:
    - user3

...

或纯 bash ...

Or pure bash...

myadduser () { 
    local crt= line;
    while IFS= read line; do
        echo "$line";
        [ "$line" ] && { 
            [ "${line:0:1}" != " " ] && crt=${line%:} || { 
                [ "${line//*([: ])}" = "users" ] &&
                    [ "$crt" = "${2:-admin}" ] &&
                        printf "    - %s\n" $1
            }
        };
    done
}

可以通过以下方式使用:

which could by used:

myadduser NewAdminUser <file.txt
admin:
  users:
    - NewAdminUser
    - user1
    - user2

read_only:
  users:
    - user3

...

或带有可选的第二个参数:

or with optional second argument:

myadduser NewWriteUser write_only
admin:
  users:
    - user1
    - user2

read_only:
  users:
    - user3

write_only:
  users:
    - NewWriteUser
    - user4

access_only:
  users:
    - user5
    - user6

但是，请

阅读 Sobrique的很好的答案！

带有 perl 或

With perl or python for prototyping like by using c for finalized programmation, you may find apropriate libraries.

使用 shell 的问题中的任何此类库也可以.

Using any of this libraries in shell could be done too.

perl -MYAML -E 'undef$/;$s = Load(<>);say@{$s->{admin}->{users}}[0];'

管理员用户数

perl -MYAML -E 'undef$/;$s = Load(<>);say scalar@{$s->{admin}->{users}};' 

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