在bash脚本中通过ssh在远程主机上执行命令

Question

我写了一个bash脚本,它应该从文件中读取用户名和IP地址,并通过ssh对它们执行命令.

这是hosts.txt:

user1 192.168.56.232
user2 192.168.56.233

这是myScript.sh:

cmd="ls -l"

while read line
do
   set $line
   echo "HOST:" $1@$2
   ssh $1@$2 $cmd
   exitStatus=$?
   echo "Exit Status: " $exitStatus
done < hosts.txt

问题是执行似乎在第一个主机完成后停止.这是输出:

$ ./myScript.sh
HOST: user1@192.168.56.232
total 2748
drwxr-xr-x 2 user1 user1    4096 2011-11-15 20:01 Desktop
drwxr-xr-x 2 user1 user1    4096 2011-11-10 20:37 Documents
...
drwxr-xr-x 2 user1 user1    4096 2011-11-10 20:37 Videos
Exit Status:  0
$

为什么会这样,我该如何解决？

Answer 1

在你的脚本中,ssh作业获得与stad相同的stdin read line,并且在你的情况下恰好会占用第一次调用的所有行.所以read line只能看到输入的第一行.

解决方案:关闭stdin ssh,或者更好地重定向/dev/null.(有些程序不喜欢stdin关闭)

while read line
do
    ssh server somecommand </dev/null    # Redirect stdin from /dev/null
                                         # for ssh command
                                         # (Does not affect the other commands)
    printf '%s\n' "$line"
done < hosts.txt

如果您不想为/ dev/null重定向循环内的每个作业,您还可以尝试以下方法之一:

while read line
do
  {
    commands...
  } </dev/null                           # Redirect stdin from /dev/null for all
                                         # commands inside the braces
done < hosts.txt


# In the following, let's not override the original stdin. Open hosts.txt on fd3
# instead

while read line <&3   # execute read command with fd0 (stdin) backed up from fd3
do
    commands...       # inside, you still have the original stdin
                      # (maybe the terminal) from outside, which can be practical.

done 3< hosts.txt     # make hosts.txt available as fd3 for all commands in the
                      # loop (so fd0 (stdin) will be unaffected)


# totally safe way: close fd3 for all inner commands at once

while read line <&3
do
  {
    commands...
  } 3<&-
done 3< hosts.txt