为什么这个while循环不循环？

Question

我有以下 bash 脚本 deploy.sh:

#!/usr/bin/env bash

# Some useful resources:
# while read ip user pass; do : http://unix.stackexchange.com/questions/92664/how-to-deploy-programs-on-multiple-machines
# -o StrictHostKeyChecking=no: http://askubuntu.com/questions/180860/regarding-host-key-verification-failed
# -T: http://stackoverflow.com/questions/21659637/how-to-fix-sudo-no-tty-present-and-no-askpass-program-specified-error
# echo $pass |: http://stackoverflow.com/questions/11955298/use-sudo-with-password-as-parameter

while read ip user pass; do 
  echo $ip
  sshpass -p "$pass" ssh $user@$ip  -o StrictHostKeyChecking=no -T "
  echo 'yo'
  "
  echo 'done'
done < servers.txt

servers.txt 包含：

53.12.45.74 my_username my_password
54.12.45.74 my_username my_password
57.12.45.74 my_username my_password
‌‌ 

据我了解，while read ip user pass; do […] done < servers.txt 应该遍历servers.txt 的所有三行。

但是，当我尝试运行它时，它只执行一次迭代：

ubuntu@server:~$ bash deploy.sh
53.12.45.74
yo
done
ubuntu@server:~$

为什么？

---

如果循环很简单：

while read ip user pass; do 
      echo $ip
done < servers.txt

它确实执行了所有三个迭代：

ubuntu@server:~$ bash deploy.sh
53.12.45.74
54.12.45.74
57.12.45.74
ubuntu@server:~$

Answer 1

sshpass 正在控制stdin 或可能替换它并导致while 循环丢失来自重定向的stdin 的输入。

要解决此问题，请避免从标准输入读取。

首先，使用while 循环将文件加载到数组中。

while read line; do
    entries+=("$line")
done < servers.txt

接下来，使用for循环解析行并在这个循环中执行sshpass。

for line in "${entries[@]}"; do
  set $line
  ip=$1
  user=$2
  pass=$3
  echo $ip
  sshpass -p "$pass" ssh $user@$ip  -o StrictHostKeyChecking=no -T "
  echo 'yo'
  "
  echo 'done'
done

第二个循环不是从stdin读取的。

但我会推荐 Rany Albeg Wein answer 使用与当前 stdin 不同的描述符。

while read ip user pass <&3; do 
  echo $ip
  sshpass -p "$pass" ssh $user@$ip  -o StrictHostKeyChecking=no -T "
  echo 'yo'
  "
  echo 'done'
done 3<servers.txt

Answer 2

#!/usr/bin/env bash

# Some useful resources:
# while read ip user pass; do : http://unix.stackexchange.com/questions/92664/how-to-deploy-programs-on-multiple-machines
# -o StrictHostKeyChecking=no: http://askubuntu.com/questions/180860/regarding-host-key-verification-failed
# -T: http://stackoverflow.com/questions/21659637/how-to-fix-sudo-no-tty-present-and-no-askpass-program-specified-error
# echo $pass |: http://stackoverflow.com/questions/11955298/use-sudo-with-password-as-parameter

while read ip user pass; do

  if [ -n "$ip" ]; then

    echo "IP[$ip] USER[$user] PASS[$pass]";

    # dont forget to uncomment this two lines here:
    #sshpass -p "$pass" ssh $user@$ip  -o StrictHostKeyChecking=no -T "
    #echo 'yo'

    echo ""; # Just a blank line"
    echo "done.";

  else
    echo "Empty value.";
  fi

done < servers.txt

所以，现在可以了。