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RSH(1C) USER COMMANDS RSH(1C)

NAME
rsh - remote shell

SYNOPSIS
rsh [ -l username ] [ -n ] hostname command

rsh hostname [ -l username ] [ -n ] command

hostname [ -l username ] [ -n ] command

AVAILABILITY
This command is available with the Networking Tools and Pro-
grams software installation option. Refer to Installing the
SunOS for information on how to install optional software.

DESCRIPTION
rsh connects to the specified hostname and executes the
specified command. rsh copies its standard input to the
remote command, the standard output of the remote command to
its standard output, and the standard error of the remote
command to its standard error. Interrupt, quit and ter-
minate signals are propagated to the remote command; rsh
normally terminates when the remote command does.

If you omit command, instead of executing a single command,
rsh logs you in on the remote host using rlogin(1C). Shell
metacharacters which are not quoted are interpreted on the
local machine, while quoted metacharacters are interpreted
on the remote machine. See EXAMPLES.

Hostnames are given in the hosts database, which may be con-
tained in the /etc/hosts file, the Yellow Pages hosts data-
base, the Internet domain name database, or some combination
of the three. Each host has one official name (the first
name in the database entry) and optionally one or more nick-
names. Official hostnames or nicknames may be given as
hostname.

If the name of the file from which rsh is executed is any-
thing other than ``rsh,'' rsh takes this name as its host-
name argument. This allows you to create a symbolic link to
rsh in the name of a host which, when executed, will invoke
a remote shell on that host. The /usr/hosts directory is
provided to be populated with symbolic links in the names of
commonly used hosts. By including /usr/hosts in your
shell's search path, you can run rsh by typing hostname to
your shell.

Each remote machine may have a file named /etc/hosts.equiv
containing a list of trusted hostnames with which it shares
usernames. Users with the same username on both the local
and remote machine may rsh from the machines listed in the

Sun Release 4.0 Last change: 17 December 1987 1
RSH(1C) USER COMMANDS RSH(1C)

remote machine's /etc/hosts file. Individual users may set
up a similar private equivalence list with the file .rhosts
in their home directories. Each line in this file contains
two names: a hostname and a username separated by a space.
The entry permits the user named username who is logged into
hostname to use rsh to access the remote machine as the
remote user. If the name of the local host is not found in
the /etc/hosts.equiv file on the remote machine, and the
local username and hostname are not found in the remote
user's .rhosts file, then the access is denied. The host-
names listed in the /etc/hosts.equiv and .rhosts files must
be the official hostnames listed in the hosts database;
nicknames may not be used in either of these files.

rsh will not prompt for a password if access is denied on
the remote machine unless the command argument is omited.

OPTIONS
-l username
Use username as the remote username instead of your
local username. In the absence of this option, the
remote username is the same as your local username.

-n Redirect the input of rsh to /dev/null. You sometimes
need this option to avoid unfortunate interactions
between rsh and the shell which invokes it. For exam-
ple, if you are running rsh and invoke a rsh in the
background without redirecting its input away from the
terminal, it will block even if no reads are posted by
the remote command. The -n option will prevent this.

The type of remote shell (sh, rsh, or other) is determined
by the user's entry in the file /etc/passwd on the remote
system.

EXAMPLES
The command:

example% rsh lizard cat lizard.file >> example.file

appends the remote file lizard.file from the machine called
lizard to the file called example.file on the machine called
example, while the command:

example% rsh lizard cat lizard.file ">>"
another.lizard.file

appends the file lizard.file on the machine called lizard to
the file another.lizard.file which also resides on the
machine called lizard.

Sun Release 4.0 Last change: 17 December 1987 2

RSH(1C) USER COMMANDS RSH(1C)

FILES
/etc/hosts
/usr/hosts/*
/etc/passwd

SEE ALSO
rlogin(1C), vi(1), ypcat(1), hosts(5), named(8c)

BUGS
You cannot run an interactive command (such as vi(1)); use
rlogin if you wish to do so.

Stop signals stop the local rsh process only; this is argu- ably wrong, but currently hard to fix for reasons too com-
plicated to explain here.

The current local environment is not passed to the remote
shell.

Sometimes the -n option is needed for reasons that are less
than obvious. For example, the command:

example% rsh somehost dd if=/dev/nrmt0 bs=20b | tar
xvpBf -

will put your shell into a strange state. Evidently, what
happens is that the tar terminates before the rsh. The rsh
then tries to write into the "broken pipe" and, instead of
terminating neatly, proceeds to compete with your shell for
its standard input. Invoking rsh with the -n option avoids
such incidents.

Note: this bug occurs only when rsh is at the beginning of a
pipeline and is not reading standard input. Do not use the
-n if rsh actually needs to read standard input. For exam-
ple,

example% tar cf - . | rsh sundial dd of=/dev/rmt0
obs=20b

does not produce the bug. If you were to use the -n in a
case like this, rsh would incorrectly read from /dev/null
instead of from the pipe.

Sun Release 4.0 Last change: 17 December 1987 3

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