题目内容
将除了前两次匹配的所有a替换为7。$ echo 'hear have Isaac eagar' | sed -e '_____________'hear have Is77c e7g7r
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将文件 tao.txt 中所有行替换为该行的字符数（命令wc -L可以获得行的长度）$ cat tao.txtTao of computer scienceIf the Tao is great,then the operating system is good.If the operating system is great,then the compiler is great.If the compiler is great,then the application is great.The user is pleased,and there is harmony in the world.$ sed -ne '_____________________' tao.txt232034332725302034
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仅打印文件hello.txt的第3行，并用-----上下包围该行：$ sed -ne _____________ hello.txt-----This game is good-----
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