在 bash 脚本中执行 sed 命令
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Execute sed command in a bash script
提问by Guille
I want to execute this comand in bash scripting.
我想在 bash 脚本中执行这个命令。
Code:
代码：
#!/bin/bash
line=39;
d=d; ## For delete line
`echo "sed '$line$d' /etc/passwd"`;
But when I execute, I got this error:
但是当我执行时，我收到了这个错误：
sed: -e expresion #1, character 1: unknow command <<'>>
I tried with echo "sed \'$line$d\' /etc/passwd";
我试过echo "sed \'$line$d\' /etc/passwd";
But same problem...
但是同样的问题...
回答by David C. Rankin
You need to insure when calling your variables that you do not prevent expansion by single-quotingthem. Now it is OK to use single-quoteswithindouble-quotes, but be mindful. Also, though not required, when putting two variables back-to-back, it is better to use braces to insure against ambiguity. That said, your sedcommand from a script works fine as:
您需要确保在调用变量时不会阻止single-quoting它们的扩展。现在可以使用single-quotesinsidedouble-quotes，但要注意。此外，虽然不是必需的，但在将两个变量背对背放置时，最好使用大括号来确保避免歧义。也就是说，您sed来自脚本的命令可以正常工作：
sed -e "${line}${d}" /etc/passwd
Which will output /etc/passwdto stdoutminus line $line. To edit /etc/passwdin place, use sed -i
这将输出/etc/passwd到stdout减号行$line。要/etc/passwd就地编辑，请使用sed -i
回答by ShellFish
To delete line 39 simply do:
要删除第 39 行，只需执行以下操作：
#!/bin/bash
line=39;
sed -i "${line}d" /etc/passwd
Sed will take the second argument as input file and the first as a command. The extra flag -iwill allow you to redirect the output immediately to the input file. Note that this is not the same as sed 'command' file > fileas this will result in an empty file.
sed 将第二个参数作为输入文件，第一个作为命令。额外的标志-i将允许您立即将输出重定向到输入文件。请注意，这sed 'command' file > file与这将导致空文件不同。
I also advise executing man sedin your shell.
我还建议man sed在你的 shell 中执行。
回答by NeronLeVelu
#!/bin/bash
# delete line 39 by editing inline via sed;
sed -i '39d' /etc/passwd
Keep it simple and add the comment if you want remember the sed action
如果您想记住 sed 操作，请保持简单并添加注释
