awk打印每第n个匹配的行，所有行都不是数学

Question

我知道如何打印每个第n行和第n个匹配的行，但不知道如何打印每个第n个匹配行和所有行都不是数学。

输入示例：

Something else 1
Downloading: file1 1%
Downloading: file1 10%
Something else 2
Downloading: file1 30%
Something else 3
Downloading: file1 40%
Downloading: file2 50%
Downloading: file1 60%
Downloading: file1 100%
Downloading: file2 100%
Something else 4

如果模式是＆＃39; ^正在下载：＆＃39;并打印每个第二个匹配的行，输出应该是这样的：

Something else 1
Downloading: file1 10%
Something else 2
Something else 3
Downloading: file1 40%
Downloading: file1 60%
Downloading: file2 100%
Something else 4

Answer 1

$ awk '!(/Downloading/ && ++c%2)' file
Something else 1
Downloading: file1 10%
Something else 2
Something else 3
Downloading: file1 40%
Downloading: file1 60%
Downloading: file2 100%
Something else 4

Answer 2

对于perl粉丝：

perl -nlE 'say unless /Downloading/ && ++$n%2'