how to run perl regex command remotely

Question

I got this command that works perfectly on the remote server

perl -ne 'print "$1,$2,$3\n" if /^[^\[]*\[\K([^]]+)[^{]*{[^[]*\["\K([^"]+)(?:(?!SmsJob).)*SmsJob:\K([0-9a-f]+)/' /path/to/file.log

but then when I try to run it locally by saving it as a shell function like so:

function getRemoteLogs()
{
    ssh -i $ssh_key_file ubuntu@$1 -t 'perl -ne `print "$1,$2,$3\n" if /^[^\[]*\[\K([^]]+)[^{]*{[^[]*\["\K([^"]+)(?:(?!SmsJob).)*SmsJob:\K([0-9a-f]+)/` /path/to/file.log' > local.txt
}

where $1 is the ip of the remote server

it returns this error:

bash: command substitution: line 0: syntax error near unexpected token `('
bash: command substitution: line 0: `print "$1,$2,$3\n" if /^[^\[]*\[\K([^]]+)[^{]*{[^[]*\["\K([^"]+)(?:(?!SmsJob).)*SmsJob:\K([0-9a-f]+)/'
Unknown regexp modifier "/w" at -e line 1, at end of line
Unknown regexp modifier "/w" at -e line 1, at end of line
Unknown regexp modifier "/w" at -e line 1, at end of line
syntax error at -e line 1, near "18.log
"
Execution of -e aborted due to compilation errors.

how do I do this?

Answer 1

The backticks you are using tell Perl to pass everything inside them to the underlying shell as a command - like exec or system() would do. Here's a link that discusses backticks in Perl.

You do need to quote the whole perl command for the remote server, but you will have to use double quotes. Then you must escape the inner double quotes and the variables that would otherwise expand.

Try this out:

ssh -i $ssh_key_file ubuntu@<remote ip> "perl -ne 'print \"\$1,\$2,\$3\n\" if /^[^\[]*\[\K([^]]+)[^{]*\{[^[]*\[\"\K([^\"]+)(?!SmsJob).)*SmsJob:\K([0-9a-f]+)/' /path/to/file.log" > local.txt

I also escaped the left brace after the glob, because perl complained about it.

Also, I don't think you need to force a pseudo tty on the connection, so you can probably drop -t. If that gives you trouble then I would try it with -T first to disable pseudo TTY creation.

Answer 2

Here are a couple of alternatives to Guy's answer.

I shortened your original command to make it (slightly) more readable:

perl -ne 'print "$1,$2,$3\n" if /^([^\[]*)(?:.*(?!SmsJob).)*/' /var/log/syslog

Now with ssh, if you put the perl code in double-quotes, you could use qq{} inside, instead of escaped double-quotes. However, you would still need to escape the $ variables:

ssh -i $id $user@$host 'perl -ne "print qq{\$1,\$2,\$3\n} if /^([^\[]*)(?:.*(?!SmsJob).)*/" /var/log/syslog'

A more readable alternative is to use the suggestion in @choroba's comment: close and reopen the quotes:

ssh -i $id $user@$host 'perl -ne ' "'" 'print "$1,$2,$3\n" if /^([^\[]*)(?:.*(?!SmsJob).)*/' "'" /var/log/syslog

or slightly shorter by keeping the first part in double-quotes:

ssh -i $id $user@$host "perl -ne '" 'print "$1,$2,$3\n" if /^([^\[]*)(?:.*(?!SmsJob).)*/' "'" /var/log/syslog

(tested with a local Ubuntu 16.04, and a remote Debian 9)