Odd quirk with xargs and telnet Post: 302458127

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Top Forums UNIX for Dummies Questions & Answers Odd quirk with xargs and telnet Post 302458127 by treesloth on Wednesday 29th of September 2010 07:49:01 PM

09-29-2010

Registered User

Odd quirk with xargs and telnet

For a variety of strange reasons, I've set up an arrangement by which a server responds with "Hi there" if I connect on a specified port. This is a typical transaction:

Code:

# telnet example.com 3334
Trying 123.456.789.101...
Connected to example.com.
Escape character is '^]'.
Hi there
Connection closed by foreign host.

Now, I'm trying to use a quick and dirty way to do this concurrently, using xarg's -P (or max-procs, in some cases) option. Once this works, I'll increase the seq value, add -P concurrency, and be happy. The problem, though, is that I can't get the server's response to show up. Here's a trivial case:

Code:

# seq 1 | xargs -I DISCARD telnet example.com 3334
Trying 123.456.789.101...
Connected to example.com.
Escape character is '^]'.
Connection closed by foreign host.

So, the "1" should be discarded, as there is no DISCARD string in the command called by xargs, and the telnet command should be run. But, this trivial case should be the same thing as just running the telnet command alone since it's wrapped up in a negligible xargs. But, for some reason, the server's "Hi there" doesn't appear. Any idea why that is? I've tried redirecting stderr to stdout on the chance that it's some oddity in the way xargs handles errors, but no luck. I've also placed the telnet command into a little one-liner script and called that instead, without changing the output. Any suggestions? I've scratched my head many times. It didn't help... Many thanks in advance.

Last edited by treesloth; 09-29-2010 at 09:18 PM..

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LEARN ABOUT DEBIAN

xrlogin

XRLOGIN(1)						      General Commands Manual							XRLOGIN(1)

NAME

       xrlogin - start an xterm that uses ssh (or optionally rlogin or telnet) to connect to a remote host

SYNOPSIS

       xrlogin [-l username] [-rlogin|-telnet] [xterm options] remote-host

DESCRIPTION

       Xrlogin opens an xterm window and runs ssh, rlogin or telnet to login to a remote host.

       Xrlogin	automatically  passes  the -name argument to xterm with a value of "xterm-hostname" where hostname is the name of the remote host.
       This allows the user to specify resources in their server's resource manager which are specific to xterms from a given host.  For  example,
       this  feature  can  be used to make all xterm windows to a given remote host be the same color or use a specific font or start up in a spe-
       cific place on the screen.  Xrsh(1) passes the same string so they are compatible in this regard.

       Xrlogin specifies that the default title for the new xterm will be "hostname" where hostname is the name of the remote host.  This and  the
       -name argument above can be overridden with xterm-options on the command line.

       One  could  also  use  xrlogin's sister command xrsh(1) to open a window to a remote host.  In the case of xrsh, the xterm would run on the
       remote host and use X as the connection protocol while xrlogin would run the xterm on the local host and use rlogin or telnet as  the  con-
       nection protocol.  See xrsh(1) for a discussion of the merits of each scheme.

OPTIONS

       -l username
	      When not using -telnet, use username as the id to login to the remote host.

       -rlogin
	      Use  the rlogin protocol to open the connection.	In general rlogin is preferred because it can be configured to not prompt the user
	      for a password.  Rlogin also automatically propagates window size change signals (SIGWINCH) to the remote host so that  applications
	      running there will learn of a new window size.

       -telnet
	      Use the -telnet protocol to open the connection. Use of telnet provided mostly for hosts that don't support rlogin.

COMMON PROBLEMS

       Make  sure  that  the  local  host  is  specified in the .rhosts file on the remote host or in the remote hosts /etc/hosts.equiv file.  See
       rlogin(1) for more information.

EXAMPLES

       xrlogin -bg red yoda
	      Start a local red xterm which connects to the remote host yoda using rlogin.

       xrlogin -telnet c70
	      Open a local xterm which connects to the remote host c70 using telnet.

SEE ALSO

       xrsh(1), rlogin(1), telnet(1)

AUTHOR

       James J. Dempsey <jjd@jjd.com> and Stephen Gildea <gildea@intouchsys.com>.

X Version 11							     Release 6								XRLOGIN(1)