Populate array to ssh in bash

Question

Just some background, I have a file with 1000 servers in it new line delimted. I have to read them to an array the run about 5 commands over SSH. I have been using heredoc notation but that seems to fail. Currently I get an error saying the host isn't recognized.

    IFS='\n' read -d '' -r -a my_arr < file
    my_arr=()
    for i in "${my_arr[@]}"; do
            ssh "$1" bash -s << "EOF"
            echo "making back up of some file"
            cp /path/to/file /path/to/file.bak
            exit
    EOF
    done

I get output that lists the first server but then all the ones in the array as well. I know that I am missing a redirect for STDIN that causes this.

Thanks for the help.

There is no $i in your script, other than as the item being iterated over. Do you want $i rather than $1? — Charles Duffy
– Charles Duffy, Commented Feb 16, 2017 at 16:25
...to be clear, this has nothing at all to do with ssh, or with heredocs. You'd have the exact same problem with any other command -- for i in "${my_arr[@]}"; do echo "$1"; done would fail in the same way. — Charles Duffy
– Charles Duffy, Commented Feb 16, 2017 at 16:26
BTW, use declare -p my_arr to print its contents unambiguously, to answer the question of whether the array is in fact correctly populated. — Charles Duffy
– Charles Duffy, Commented Feb 16, 2017 at 16:27
As a second aside -- EOF is only honored as the end of a heredoc if not indented. If your real file isn't indented, the use only a four-space indent in your question to accurately reflect that, rather than the eight-space indent given here. — Charles Duffy
– Charles Duffy, Commented Feb 16, 2017 at 16:32

arco444 · Accepted Answer · 2017-02-16 16:21:24Z

2

Do you need an array? What is wrong with:

while read -r host
do
  ssh "$host" bash -s << "EOF"
  echo "making back up of some file"
  cp /path/to/file /path/to/file.bak
EOF
done < file

edited Feb 16, 2017 at 16:21

answered Feb 16, 2017 at 15:41

arco444

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2 Comments

zinnadean Over a year ago

using the EOF in the loop causes the file to end. Since you can use anything I've changed it to END. This resolves the issue.

Charles Duffy Over a year ago

@zinnadean, the string EOF does not cause the file to end, unless the file itself is enclosed in a larger heredoc using that same sigil. In short, that problem can only be caused if you've got extra context not included in your question.

Charles Duffy · Accepted Answer · 2017-02-16 16:30:51Z

0

To be clear -- the problem here, and the only problem present in the code actually included in your question, is that you're using $1 inside your loop, whereas you specified $i as the variable that contains the entry being iterated over on each invocation of the loop.

That is to say: ssh "$1" needs to instead by ssh "$i".

answered Feb 16, 2017 at 16:30

Charles Duffy

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2 Comments

zinnadean Over a year ago

It was an error when I transcribed it. It should be "$i".

Charles Duffy Over a year ago

Then your original code is, in and of itself, fine -- and your bug is something that only takes place in the context of code you didn't provide in the question.

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