sed

sed - 如何只获取被替换的最后一行？(sed - How to get only the last line that was substituted?)

我试图获得一个sed -only（或者只是一个awk -only）解决方案，它只输出与替换模式匹配的最后一行。

到目前为止，我有一个解决方案，只输出匹配模式的行，但我不知道如何只提取这些剩余的行的最后一行。 我尝试了$!d ，但它只从初始输入中提取最后一行。

sed -E '/^.*\*\ *(Command Line Tools.*)\ *$/!d;s//\1/'

样本输入：

Software Update Tool Copyright 2002-2015 Apple Inc. Software Update found the following new or updated software: * Command Line Tools (OS X 10.11) for Xcode-7.3 Command Line Tools (OS X 10.11) for Xcode (7.3), 178678K [recommended] * Command Line Tools (macOS Sierra version 10.12) for Xcode-8.1 Command Line Tools (macOS Sierra version 10.12) for Xcode (8.1), 123638K [recommended]

样本输出：

Command Line Tools (macOS Sierra version 10.12) for Xcode-8.1

I'm trying to get a sed-only (or alternatively an awk-only) solution which only outputs the last line which matches the substitution pattern.

So far I have a solution which outputs only the lines that match the pattern, but I don't know how to extract only the last line of these remaining ones. I tried $!d, but it only extracts the last line from the initial input.

sed -E '/^.*\*\ *(Command Line Tools.*)\ *$/!d;s//\1/'

Sample Input:

Software Update Tool Copyright 2002-2015 Apple Inc. Software Update found the following new or updated software: * Command Line Tools (OS X 10.11) for Xcode-7.3 Command Line Tools (OS X 10.11) for Xcode (7.3), 178678K [recommended] * Command Line Tools (macOS Sierra version 10.12) for Xcode-8.1 Command Line Tools (macOS Sierra version 10.12) for Xcode (8.1), 123638K [recommended]

Sample Output:

Command Line Tools (macOS Sierra version 10.12) for Xcode-8.1

最满意答案

您可以使用以下GNU sed命令：

sed -n '/PATTERN/H;${x;s/.*\n//;p}' file

说明：

sed -n默认禁止输出 /PATTERN/是您要匹配的模式 H将当前匹配的行追加到保持缓冲区 $地址输入的最后一行（仅在GNU sed上可用） x交换保持和模式缓冲区的内容 s/.*\n//替换包括模式缓冲区中最后一个换行符在内的所有内容。 这实际上只留下了最后一场比赛 - 正如你所要求的那样。 p打印出来。

You can use the following GNU sed command:

sed -n '/PATTERN/H;${x;s/.*\n//;p}' file

Explanation:

sed -n Suppresses output by default /PATTERN/ is the pattern you want to match H Appends the current, matching, line to the hold buffer $ Addresses the last line of input (available only on GNU sed) x Exchange the contents of the hold and patter buffer s/.*\n// Replaces everything including the last newline in pattern buffer. This effectively leaves just the last match - as you've asked for. p Prints it.