Bash尝试在Heredoc中执行命令 [英] Bash tries to execute commands in heredoc

问题描述

我正在尝试编写一个简单的bash脚本，该脚本将多行输出打印到另一个文件.我正在通过heredoc格式进行操作:

I am trying to write a simple bash script that will print a multiline output to another file. I am doing it through heredoc format:

#!/bin/sh

echo "Hello!"
cat <<EOF > ~/Desktop/what.txt
a=`echo $1 | awk -F. '{print $NF}'`
b=`echo $2 | tr '[:upper:]' '[:lower:]'`
EOF

我希望在桌面上看到包含以下内容的文件:

I was expecting to see a file in my desktop with these contents:

a=`echo $1 | awk -F. '{print $NF}'`
b=`echo $2 | tr '[:upper:]' '[:lower:]'`

但是，相反，我将这些内容视为我的what.txt文件的内容:

But instead, I am seeing these as the contents of my what.txt file:

a=
b=

以某种方式，即使它是heredoc的一部分，bash仍试图逐行执行它.我该如何防止这种情况，并将内容按原样打印到文件中?

Somehow, even though it is part of a heredoc, bash is trying to execute it line by line. How do I prevent this, and print the contents to the file as it is?

推荐答案

引用EOF，以便bash从字面上接受输入:

Quote EOF so that bash takes inputs literally:

cat <<'EOF' > what.txt
a=`echo $1 | awk -F. '{print $NF}'`
b=`echo $2 | tr '[:upper:]' '[:lower:]'`
EOF

也开始使用$()代替旧的和有问题的``.c5>来代替命令.

Also start using $() for command substitution instead of old and problematic ``.

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