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Bash尝试在heredoc中执行命令

[英]Bash tries to execute commands in heredoc

I am trying to write a simple bash script that will print a multiline output to another file. 我正在尝试编写一个简单的bash脚本,它将多行输出打印到另一个文件。 I am doing it through heredoc format: 我是通过heredoc格式来做的:

#!/bin/sh

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

I was expecting to see a file in my desktop with these contents: 我期待在桌面上看到包含以下内容的文件:

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

But instead, I am seeing these as the contents of my what.txt file: 但相反,我将这些视为what.txt文件的内容:

a=
b=

Somehow, even though it is part of a heredoc , bash is trying to execute it line by line. 不知何故,即使它是heredoc一部分,bash也试图逐行执行它。 How do I prevent this, and print the contents to the file as it is? 如何防止这种情况,并将内容按原样打印到文件中?

Quote EOF so that bash takes inputs literally: 引用EOF以便bash字面输入:

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

Also start using $() for command substitution instead of old and problematic ``. 也开始使用$()进行命令替换而不是旧的和有问题的``。

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