无法通过 SSH 在 heredoc 或命令中使用本地和远程变量 [英] Unable to use local and remote variables within a heredoc or command over SSH

问题描述

下面是一个使用 heredoc 的 ssh 脚本示例(实际脚本更复杂).是否可以在 SSH heredoc 或命令中同时使用本地和远程变量?

Below is an example of a ssh script using a heredoc (the actual script is more complex). Is it possible to use both local and remote variables within an SSH heredoc or command?

FILE_NAME 在本地服务器上设置，以便在远程服务器上使用.REMOTE_PID 在远程服务器上运行时设置，以便在本地服务器上使用.FILE_NAME 在脚本中被识别.REMOTE_PID 未设置.

FILE_NAME is set on the local server to be used on the remote server. REMOTE_PID is set when running on the remote server to be used on local server. FILE_NAME is recognised in script. REMOTE_PID is not set.

如果将 EOF 更改为 'EOF'，则设置 REMOTE_PID 而不会设置 `FILE_NAME.我不明白这是为什么?

If EOF is changed to 'EOF', then REMOTE_PID is set and `FILE_NAME is not. I don't understand why this is?

有没有办法同时识别REMOTE_PID 和FILE_NAME?

Is there a way in which both REMOTE_PID and FILE_NAME can be recognised?

正在使用 bash 的第 2 版.默认远程登录为cshell，本地脚本为bash.

Version 2 of bash being used. The default remote login is cshell, local script is to be bash.

FILE_NAME=/example/pdi.dat
ssh user@host bash << EOF
# run script with output...
REMOTE_PID=$(cat $FILE_NAME)
echo $REMOTE_PID
EOF
echo $REMOTE_PID

推荐答案

如果不想扩展变量，则需要转义 $ 符号:

You need to escape the $ sign if you don't want the variable to be expanded:

$ x=abc
$ bash <<EOF
> x=def
> echo $x   # This expands x before sending it to bash. Bash will see only "echo abc"
> echo $x  # This lets bash perform the expansion. Bash will see "echo $x"
> EOF
abc
def

所以在你的情况下:

ssh user@host bash << EOF
# run script with output...
REMOTE_PID=$(cat $FILE_NAME)
echo $REMOTE_PID
EOF

或者，您也可以只使用带单引号的此处字符串:

Or alternatively you can just use a herestring with single quotes:

$ x=abc
$ bash <<< '
> x=def
> echo $x  # This will not expand, because we are inside single quotes
> '
def

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