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How can I make cat someFile | ssh someHost work when someFile is not a bash script? I want to remotely execute a perl script but I get a bunch of syntax errors from bash when I try the cat | ssh command.

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If you want to push the Perl script through the SSH connection, you'll have to run the Perl interpreter on the remote end. It'll read the script from stdin:

ssh remotehost perl < somescript.pl

In the case of Perl, it should even read the command line switches (except -T) from the hashbang line of the input.

If you want to give command line arguments to the Perl interpreter, you can just add them to the command line after perl. If you want to give arguments to the script, you'll need to explicitly tell the interpreter to read the script from stdin (otherwise it will take the first argument as a file name to look for).

So, here -l goes to the interpreter, and foo and bar to the script:

echo 'print "> $_"  foreach @ARGV' | ssh remotehost perl -l - foo bar 

Note that doing just ssh somehost < script.sh counts on the remote login shell being compatible with the script. (i.e. a Bash script won't work if the remote shell happens to be something else.)

  • I've found that cat perlScript | ssh remoteHost perl works great. I'd like to pass a command line argument to perl. Do you know how I might do that? – Sol Mar 22 '17 at 17:30
  • @Sol, edited, since there's a slight difference between switches to perl and what goes to the script's @ARGV – ilkkachu Mar 22 '17 at 17:59
  • A friend suggested this and it works great! cat perlScript | ssh remoteHost perl /dev/stdin someArgument The /dev/stdin part is most interesting. – Sol Mar 22 '17 at 18:18
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ssh someHost will execute your default shell, which in turn will execute the commands it reads from standard input. Since you are sending the content of someFile to standard input, it logically tries to executes to content of someFile.

You don't tell us what someFile is supposed to contain. Assuming its content is supposed to be fed to your perl script, what you should do is:

cat someFile | ssh someHost your_perl_script

Or better:

ssh someHost your_perl_script < someFile
  • someFile is the perl script I want to execute remotely. Sorry I wasn't clear in the problem description. – Sol Mar 22 '17 at 17:32
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in ordred to =>

Write local output into remote file: You just installed the apache on your $myhost. Now you want to test it.

You can echo the test string into file, only this time the file is in remote htdocs root:

echo "It works" | ssh user@your.host 'cat >> /usr/local/apache/htdocs/it_works.html'

Open remote file with less or cat: With cat:

ssh user@your.host "cat /usr/local/apache/htdocs/it_works.html"

With less:

ssh user@your.host "less /usr/local/apache/htdocs/it_works.html"

Grep remote files:

With pipe:

ssh user@your.host "cat /usr/local/apache/htdocs/it_works.html" |  grep "works"

Just remote grep:

ssh user@your.host "grep works /usr/local/apache/htdocs/it_works.html"

Watching remote logs with tail:

This way you can watch the access to apache server in real-time:

 ssh user@your.host "tail -f /etc/httpd/logfiles/access_log"

The source for this answer is here.

  • 2
    Running less on the remote like that is a bit bare, since by default SSH (without -t) doesn't allocate a terminal if a command line is given, so less only sees a socket, and most of its functionality is lost. – ilkkachu Mar 22 '17 at 17:04
  • 1
    Does any of this answer the question here, anyway? – ilkkachu Mar 22 '17 at 17:04
  • I'm trying to remotely execute a perl script. I think this may not be possible without copying the perl script to the remote machine. – Sol Mar 22 '17 at 17:18
  • check @ilkkachu answer. – Kingofkech Mar 22 '17 at 17:28

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