My while read command isn't opening a while loop

I'm trying to use the while read command to create a comma separated table of names, routers, and IP addresses. It should then SSH through that series of routers with the router1 value, input a command, and extract the IP addresses it should return, then write them to a file. It is my understanding that I can do this with read.

 grep -v '^#' /opt/pp1/projectprefixed/peeringinfo > /opt/pp1/projectprefixed/$DATE/peeringinfo.conf

ip_regex='([0-9]{1,3}\.){3}[0-9]{1,3}'

while IFS=, read NREN router1 peering
do

  if [ ! -f /opt/pp1/projectprefixed/$DATE/recFromNRENList/$router1 ] 
    then
    ssh -q -n -o StrictHostKeyChecking=no srv_oc_scripts@$router1 "show route recieve-protocol bgp" | grep -o "$ip_regex" > peeringsReceived
  fi

done < $router1

The table is a text like that looks like this:

NAME1,mx1.ROUTER1,192.168.1.1
NAME2,mx1.ROUTER2,192.168.65.7

However, it returns an "ambiguous redirect" error.

There are several major logic errors

1. ssh will consume stdin. Read from a different file descriptor

   while IFS= read -r NREN router1 peering <&3; do
     ...
   done 3< 4router1
   

2. router1 appears to be initialized in the read command, but is used as an input file to the loop beforehand, and as the ssh remote host, and as a file name you test for existence, and as the output file for the loop commands. I can't tell how this file is supposed to exist, and what contents it's supposed to have
3. grep will also consume stdin: You probably forgot to specify what input you want for grep

> I want to ssh into a router, run the specified command and pull only the matching pattern and write it to a file. It's meant to be an IP address

As a wile stab in the dark, perhaps you want

ip_regex='([0-9]{1,3}\.){3}[0-9]{1,3}'
output_dir="/opt/pp1/projectprefixed/$DATE/recFromNRENList"
router1=???

ip_addr=$(
    ssh -q -n -o StrictHostKeyChecking=no \
        "srv_oc_scripts@$router1" \
        "show route recieve-protocol bgp" \
    | grep -o "$ip_regex"
)


</details>



# 答案2
**得分**: 0

重定向在执行任何命令之前进行设置。
这意味着发送到 while 循环的输入重定向永远不会更新，并且始终读取 "router1" 的初始值作为输入。

在简化的代码形式中，我们在这里创建两个文件，然后在 while 循环中读取 `foo` 并尝试在运行中更改 while 循环的输入文件。

```bash
#!/usr/bin/env bash
echo $'bar\nbaz' > foo
echo $'qux' > bar
f=foo;i=0
while read -r f; do echo $f; f=bar; done < "$f"
grep . *

这不起作用，因为 while 循环的输入被分配给与 foo 相连接的文件指针，您无法更改它。

错误的原因是什么？最有可能与 https://stackoverflow.com/questions/2462385/getting-an-ambiguous-redirect-error 有关。

最有可能的情况是，在 while 循环之前忘记为 router1 赋值，或者局部于 while 循环的变量 router1 为空。这与链接问题中提到的错误一致。

#!/usr/bin/env bash
echo $'bar\nbaz' > foo
echo $'qux' > bar
f=foo;i=0
while read -r f; do echo $f; f=bar; done < "$f"
grep . *