Bash:如何使用sed仅替换文件中的最后一次出现? [英] Bash: how to use sed to replace only the last occurence in a file?

问题描述

具有包含重复的注释行的文件，例如:

Having a file containing repeated commented lines like:

# ScriptAlias /cgi-bin/ "somepath"
# ScriptAlias /cgi-bin/ "otherpath"

我只想在最后一次出现后添加一行

I want to add a line only after the last occurence resulting in

# ScriptAlias /cgi-bin/ "somepath"
# ScriptAlias /cgi-bin/ "otherpath"
ScriptAlias /cgi-bin/ "mypath"

为此，我正在使用以下命令:

To do so I'm using this command:

sed -i 's:^\(.*ScriptAlias /cgi-bin/.*\):\1 \nScriptAlias /cgi-bin/ "mypath":' file

但这会导致每次出现后添加我的行，例如:

But this results in adding my line after each occurence like:

# ScriptAlias /cgi-bin/ "somepath"
ScriptAlias /cgi-bin/ "mypath"
# ScriptAlias /cgi-bin/ "otherpath"
ScriptAlias /cgi-bin/ "mypath"

我如何告诉sed仅替换最后一次出现的事件?

已编辑:
如果没有办法使用sed来解决它(如评论中所述)，请提供达到相同结果的替代方法，谢谢.

How can I tell sed to replace only the last occurence?

EDITED:
If there's no way to solve it using sed (as said in comments), please provide alternatives reaching the same result, thanks.

已编辑:
重复的行可以分开，并且它们之间可以有其他行

EDITED:
The repeated lines can be separeted and with other lines between them like

# ScriptAlias /cgi-bin/ "somepath"
# ScriptAlias /cgi-bin/ "otherpath"

# ScriptAlias /cgi-bin/ "another-path"
ScriptAlias /foo/ "just-jump"
# ScriptAlias /cgi-bin/ "that's the last"

推荐答案

使用 tac ，以便先在上打印新行当您看到模式时:

Use tac so you print your new line the first time you see the pattern:

tac file | awk '/ScriptAlias/ && ! seen {print "new line"; seen=1} {print}' | tac

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