防止“回声"从解释反斜杠转义 [英] Prevent "echo" from interpreting backslash escapes

问题描述

我想向包含新行转义序列的文件回显某些内容，但是我希望它们保持转义状态.我正在寻找与这个问题基本相反的东西. >

I'd like to echo something to a file that contains new line escape sequences, however I would like them to remain escaped. I'm looking for basically the opposite to this question.

echo "part1\npart2" >> file

我想在文件中看起来像这样

I would like to look like this in the file

$ cat file
old
part1\npart2

但是看起来像

$ cat file
old
part1
part2

推荐答案

这是POSIX建议使用printf而不是echo的一个很好的例子(请参阅echo ¹ .

This is a good example of why POSIX recommends using printf instead of echo (see here, under "application usage"): you don't know what you get with echo¹.

您可以获得:

• 默认情况下不解释反斜杠转义的内置Shell echo
  • 示例:内置的Bash echo具有-e选项以启用反斜杠转义解释并检查xpg_echo shell选项
  • A shell builtin echo that does not interpret backslash escapes by default
    • Example: the Bash builtin echo has an -e option to enable backslash escape interpretation and checks the xpg_echo shell option
    • 示例:zsh，破折号

    POSIX规范说明了这一点(重点是我):

    The POSIX spec says this (emphasis mine):

    应支持以下操作数:
    string
    要写入标准输出的字符串.如果第一个操作数是-n，或者任何操作数包含<backslash>字符，则结果是实现定义的.

    The following operands shall be supported:
    string
    A string to be written to standard output. If the first operand is -n, or if any of the operands contain a <backslash> character, the results are implementation-defined.

    因此，对于便携式解决方案，我们可以使用printf:

    So, for a portable solution, we can use printf:

    printf '%s\n' 'part1\npart2' >> file
    

    其中格式字符串中的\n将始终被解释，而参数中的\n将永远不会被解释，从而导致

    where the \n in the format string will always be interpreted, and the \n in the argument will never be interpreted, resulting in

    part1\npart2
    

    被附加到file.

    ¹ 有关echo和printf各种行为的详尽概述，请参见

    ¹ For an exhaustive overview of various behaviours for echo and printf, see echo(1) and printf(1) on in-ulm.de.

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