在Linux的特定位置添加一行并输出到同一文件? [英] Add a line in a specific position with Linux and output to the same file?

问题描述

如何在file.txt中添加第三行:

How to add a third line in file.txt:

             line 1
             line 2
             line 4

sed可以处理 sed'3iline 3'file.txt ，但是我想输出到同一文件.我尝试 sed'3iline 3'file.txt>>file.txt 无效.它确实添加了行，但是它复制了file.txt，我得到了:

sed could do with sed '3iline 3' file.txt but I want to output to the same file. I tried sed '3iline 3' file.txt >> file.txt which didn't work. It did add the line but it duplicates file.txt, I got this:

       line 1
       line 2
       line 4
       line 1
       line 2
       line 3
       line 4

推荐答案

执行此操作的唯一方法是写入第二个文件，然后替换原始文件.您只能追加到任意文件；您不能插入其中一个.

The only way to do this is to write to a second file, then replace the original. You can only append to an arbitrary file; you cannot insert into the middle of one.

t=$(mktemp)
sed '3iline 3' file.txt > "$t" && mv "$t" file.txt

如果您的 sed 版本支持该功能，则可以使用 -i 选项自动处理临时文件.

If your version of sed supports it, you can use the -i option to automate the handling of the temporary file.

sed -i '3iline 3' file.txt  # GNU
sed -i "" '3iline 3 ' file.txt  # BSD sed requires an argument for -i

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