SED 在 d(elete)、a(ppend) 或 c(hange) 之后不处理 {} 中的多个命令

Question

sed应该在匹配模式后处理多个命令 ，这些命令在{cmd1;cmd2;cmd3}等大括号中给出。但是在下面给定的代码中，d(elite) 之后的所有命令都将被忽略。

脚本文件

s/^\(interface GigabitEthernet0\)$/\1\/0/
/interface GigabitEthernet0\/0$/{
n       # process next line = 1st line (after match) to be deleted
d       # Should delete '1st line (after match) to be deleted'
n       # process next line = 2nd line to be altered
s/2nd line to be altered/2ND LINE AFTER ALTERATION/
n
s/3rd line to be altered/3RD LINE AFTER ALTERATION/
}

输入文件

interface GigabitEthernet0
  1st line (after match) to be deleted
  2nd line to be altered
  3rd line to be altered
  4th line stays unchanged

sed -i -f 脚本.sed 示例.txt

预期输出：

interface GigabitEthernet0/0
  2ND LINE AFTER ALTERATION
  3RD LINE AFTER ALTERATION
  4th line stays unchanged

有效输出：

interface GigabitEthernet0/0
  2nd line to be altered
  3rd line to be altered
  4th line stays unchanged

如上面的输出所示，要删除的第 1 行（匹配后）已被有效删除。但是以下所有行（第 2、第 3、第 4 行）都不会被替换。

顺便说一句：像 a(ppend) 或 c(hange) 这样的命令的行为方式相同；所有跟随的命令都将被忽略。

Answer 1

sed 用于执行 s/old/new，仅此而已。只需使用 awk，例如使用 GNU awk 进行就地编辑（就像使用 GNU sed 一样）和 switch 语句：

$ cat tst.awk
/^interface GigabitEthernet0$/ { lineNr=1 }
lineNr%5 {
    switch (lineNr++) {
    case 1: $0 = $0 "/0";               break
    case 2: next;                       break
    case 3: sub(/2nd line/,"WHATEVER"); break
    case 4: $0 = toupper($0);           break
    }
}
{ print }

$ cat file
interface GigabitEthernet0
  1st line (after match) to be deleted
  2nd line to be altered
  3rd line to be altered
  4th line stays unchanged

$ awk -i inplace -f tst.awk file

$ cat file
interface GigabitEthernet0/0
  WHATEVER to be altered
  3RD LINE TO BE ALTERED
  4th line stays unchanged

万一您确实只想打印新行，而不是在匹配正则表达式后修改范围内的现有行（如@AlexHarvey 的 sed 答案），那么那就是：

awk '/interface GigabitEthernet0/ {
    print $0 "/0\n  2ND LINE AFTER ALTERATION\n  3RD LINE AFTER ALTERATION"
    c = 4
}
!(c&&c--)' file
interface GigabitEthernet0/0
  2ND LINE AFTER ALTERATION
  3RD LINE AFTER ALTERATION
  4th line stays unchanged

请参阅/sf/answers/1253987381/上的常见 awk 习语列表了解c&&c--其含义。

请注意，您不必多次指定初始正则表达式，不必担心替换文本中可能会显示哪些字符，并且您只需给出一个数字来表示不受影响的行数需要多次写入相同的字符。