SSH私钥登录多远程主机脚本循环终止问题解决

问题原因 #

SSH命令默认会读取标准输入（stdin），而你的while循环是从输入文件读取stdin内容。第一次执行SSH时，会把输入文件中剩下的所有行当作自己的输入消耗掉，导致循环只处理第一台主机就终止。

解决方法 #

方法1：给SSH添加-n参数

-n参数会让SSH从/dev/null读取输入，避免占用脚本的stdin，修改所有SSH命令即可：

#!/bin/bash

# Check if the user provided a file
if [ $# -eq 0 ]; then
    echo "provide input file"
    echo "Usage: $0 <input_file>"
    exit 1
fi

# Read input file
input_file=$1

# Check if the file exists
if [ ! -f "$input_file" ]; then
    echo "Error: File $input_file not found."
    exit 1
fi

# Read each line from the input file
while IFS=, read -r ip_address username; do
    echo "Machine IP: $ip_address"
    # Connect to the server via SSH and execute the command
    echo "System Users:"
    ssh -n -i /home/subash/Desktop/privatekey "$username"@"$ip_address" "ls -l /home/ | awk 'NR >1 {print \$3}'" 2>/dev/null
    echo "---------------"
    echo "Disk details:"
    ssh -n -i /home/subash/Desktop/privatekey "$username"@"$ip_address" 'lsblk -o name,model,size,ro,mountpoint,type | grep -e part -e disk' 2>/dev/null
    echo "---------------"
    echo "OPERATING SYSTEM:"
    ssh -n -i /home/subash/Desktop/privatekey "$username"@"$ip_address" "cat /etc/os-release | grep '^NAME' | cut -d'=' -f2-" 2>/dev/null
    echo "---------------"  
done < "$input_file"

注：顺便统一了私钥的绝对路径，避免后续SSH命令找不到私钥的问题

方法2：重定向SSH输入到/dev/null

如果不想用-n参数，也可以在每个SSH命令末尾加上< /dev/null，效果和-n一致：

ssh -i /home/subash/Desktop/privatekey "$username"@"$ip_address" "ls -l /home/ | awk 'NR >1 {print \$3}'" 2>/dev/null < /dev/null

方法3：使用独立文件描述符读取输入

把输入文件绑定到独立的文件描述符（比如3），让while循环从这个描述符读取，彻底避免和SSH的stdin冲突：

#!/bin/bash

# Check if the user provided a file
if [ $# -eq 0 ]; then
    echo "provide input file"
    echo "Usage: $0 <input_file>"
    exit 1
fi

# Read input file
input_file=$1

# Check if the file exists
if [ ! -f "$input_file" ]; then
    echo "Error: File $input_file not found."
    exit 1
fi

# 绑定输入文件到文件描述符3
exec 3< "$input_file"
# 从描述符3读取每行内容
while IFS=, read -r ip_address username <&3; do
    echo "Machine IP: $ip_address"
    # Connect to the server via SSH and execute the command
    echo "System Users:"
    ssh -i /home/subash/Desktop/privatekey "$username"@"$ip_address" "ls -l /home/ | awk 'NR >1 {print \$3}'" 2>/dev/null
    echo "---------------"
    echo "Disk details:"
    ssh -i /home/subash/Desktop/privatekey "$username"@"$ip_address" 'lsblk -o name,model,size,ro,mountpoint,type | grep -e part -e disk' 2>/dev/null
    echo "---------------"
    echo "OPERATING SYSTEM:"
    ssh -i /home/subash/Desktop/privatekey "$username"@"$ip_address" "cat /etc/os-release | grep '^NAME' | cut -d'=' -f2-" 2>/dev/null
    echo "---------------"  
done
# 关闭文件描述符3
exec 3<&-

内容的提问来源于stack exchange，提问作者Subash