linux - 在shell脚本中的远程ssh命令中传递变量

Question

目前我有这个文件...

#!/usr/bin/env bash

DIRECTORY=$1

ssh root@example.com "$( cat <<'EOT'
cd /web/$DIRECTORY || exit
pwd
unset GIT_DIR
git log --oneline -n 10 --decorate
git branch
EOT
)";

为什么 pwd 只打印出“/web/”？它实际上似乎并没有使用我的变量。然后所有的 git 命令都会抛出关于在 web 目录中的错误。

如果我在 ssh-ing 之前让它回显 $DIRECTORY，它会回显我的变量，但拒绝将它传递给 ssh 命令？

Answer 1

发生这种情况是因为您引用了此处的文档定界符。这是 POSIX :

If any character in word is quoted, the delimiter is formed by performing quote removal on word, and the here-document lines will not be expanded. Otherwise, the delimiter is the word itself.

下面是一个例子:

#!/bin/bash
var=42

cat << 'end'
With quotes: $var and \$var
end

cat << end
Without quotes: $var and \$var
end

执行时:

With quotes: $var and \$var
Without quotes: 42 and $var