expect command in bash script failing

Question

I have been tweaking this for quite a bit and I am stuck with a strange output stream and no result. Basically, I'm trying to find certain ssh devices on our expansive network that have a specific password and processor. Here is the script:

#/bin/bash
for i in 54
do
  for j in 1 13 14 15
  do
    out=$(expect -c "spawn /usr/bin/ssh [email protected].$i.$j cat /proc/cpuinfo | grep MyString
      expect {
        -re \".*Are.*.*yes.*no.*\" {
        send \"yes\n\"
        exp_continue
        }

        \"*?assword:*\" {
        send \"mypasswd\"
        send \"\n\"
        exp_continue
        }
      }")
    if [["$out" != ""]]
    then
      echo "10.2.$i.$j" >> rpiout.txt
    fi
  done
done

The ssh command works by itself, just fine. Also, the expect script works fine. ALSO, if I insert an "echo $out" right before the "if [[...]]" statement, I get the expected output from the SSH command. Trying to write the file, however, I get this output to the command line and NO log file...:

./check.sh: line 19: [[spawn /usr/bin/ssh some_guy:@10.2.54.1 cat /proc/cpuinfo | grep MyString
some_guy:@10.2.54.1's password:
Permission denied, please try again.
some_guy:@10.2.54.1's password:
Permission denied, please try again.
some_guy:@10.2.54.1's password:
: No such file or directoryy,password).
./check.sh: line 19: [[spawn /usr/bin/ssh some_guy:@10.2.54.13 cat /proc/cpuinfo | grep MyString
some_guy:@10.2.54.13's password:
: No such file or directory
./check.sh: line 19: [[spawn /usr/bin/ssh some_guy:@10.2.54.14 cat /proc/cpuinfo | grep MyString
some_guy:@10.2.54.14's password:
: No such file or directory
: No such file or directoryawn /usr/bin/ssh some_guy:@10.2.54.15 cat /proc/cpuinfo | grep MyString

The first one asking for the password 3 times is correct (because it is not one of the target devices). The second 2 are non-existant IP devices, but the last 2 should return a positive result.

Note that in the "error" "./check.sh: line 19: [[spawn...", line 19 is the one that starts with "if [[...".

Any help to get me out of this mess is greatly appreciated!!

what can you see when the top line would be #!/bin/bash -vx? — Stefan Hegny
– Stefan Hegny, Commented May 24, 2016 at 6:32

glenn jackman · Accepted Answer · 2016-05-24 11:01:41Z

1

in bash [[ is not just syntax, it's a command. Like any other command, it requires whitespace to separate it from its arguments.

Not

if [["$out" != ""]]

but

if [[ "$out" != "" ]]

or

if [[ -n "$out" ]]

Additionally, due to the way expect echoes the command just like you'd see at the terminal, it's unlikely that the output will ever be empty. Try something like this:

out=$( expect <<END
    spawn -noecho /usr/bin/ssh [email protected].$i.$j sh -c {grep -q MyString /proc/cpuinfo || echo _NOT_FOUND_}
    expect {
        -re ".*Are.*.*yes.*no.*" {
            send "yes\r"
            exp_continue
        }
        "*?assword:*" {
            send "mypasswd\r"
            exp_continue
        }
        eof
    }
END
)

if [[ $out == *_NOT_FOUND_* ]]; then
    echo "MyString not found on host 10.2.$i.$j"
fi

Where _NOT_FOUND_ is some string that you would not see in /proc/cpuinfo

The -noecho is crucial here to keep "_NOT_FOUND_" out of $out unless you echo it.

answered May 24, 2016 at 11:01

glenn jackman

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1 Comment

mobrien118 Over a year ago

The space was the issue... DOH! Between posting and seeing your answer I changed the logic to be more specific than just looking for any output. I was looking for a string match, so the echo deal didn't come into play, but I will keep it in mind for the future. Thanks!!

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