rsh(1) UNIX System V(Internet Utilities) rsh(1)
NAME
rsh - remote shell
SYNOPSIS
rsh [ -n ] [ -l username ] hostname command
rsh hostname [ -n ] [ -l username ] command
hostname [ -n ] [ -l username ] command
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 terminate 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(1). 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 contained in the
/etc/hosts file, the Internet domain name database, or both. Each host
has one official name (the first name in the database entry) and
optionally one or more nicknames. Official hostnames or nicknames may be
given as hostname.
If the name of the file from which rsh is executed is anything other than
rsh, rsh takes this name as its hostname 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. By creating a directory and
populating it with symbolic links in the names of commonly used hosts,
then including the directory 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 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 hostnames 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.
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rsh will not prompt for a password if access is denied on the remote
machine unless the command argument is omitted.
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 example, 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, the restricted shell-/usr/lib/rsh, or
other) is determined by the user's entry in the file /etc/passwd on the
remote system.
EXAMPLES
The command:
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 local machine, while the command:
rsh lizard cat lizard.file ">>" lizard.file2
appends the file lizard.file on the machine called ``lizard'' to the file
lizard.file2 which also resides on the machine called ``lizard.''
FILES
/etc/hosts
/etc/passwd
SEE ALSO
rlogin(1), vi(1), named(1M), hosts(4), hosts.equiv(4)
NOTES
When a system is listed in hosts.equiv, its security must be as good as
local security. One insecure system listed in hosts.equiv can compromise
the security of the entire system.
You cannot run an interactive command [such as vi(1)]; use rlogin if you
want to do so.
Stop signals stop the local rsh process only; this is arguably wrong, but
currently hard to fix for reasons too complicated to explain here.
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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:
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.
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 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.
Prior to Release 4, the rsh command invoked the restricted shell. This
restricted shell command is /usr/lib/rsh and can be executed by using the
full pathname.
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