NAME
rexec -- remote execution client for an exec server
SYNOPSIS
rexec [ -abcdhns -l username
-p password ] host command
DESCRIPTION
Rexec calls the
routine to act as a client for the remote host's rexecd(8)
server.
It asks that ``command'' be run on the host computer, using
username/password authentication. See
and rexecd(8)
for details of the protocol.
OPTIONS
Rexec accepts several options, but only
three are likely to be very useful:
-l username
- Set the log-in name on the remote host to username.
-p password
- Provide the password for the remote account. The command line
argument will be blanked after being parsed, to prevent it from
being seen with ps(1).
However, it is still not very secure to type the password on the
command line. In particular, be sure that the shell's history file
is protected.
- -n
- Explicitly prompt for name and password, even if provided in
the environment, in the $HOME/.netrc file, or in the environmental
variables REXEC_USER and REXEC_PASS.
Other options that might be useful with non-standard remote exec
daemons, or to debug connections:
- -a
- Do not set up an auxiliary channel for standard error from
command; the remote standard error and output are then both
returned on the local standard output. By default, rexec
asks that a separate channel be set up for diagnostic output from
the remote command.
- -b
- Use signal handling as in BSD rsh(1). Only the
signals SIGINT, SIGQUIT, and SIGTERM are echoed to the remote
process. They do not remain raised locally, so rexec waits for the
remote command to shutdown its side of the socket. Also, CNTRL-Z
will only suspend execution locally--the remote command may
continue to run.
- -c
- Do not close remote standard input when local standard input
closes. Normally the standard input to the remote command is closed
when the local standard input is closed.
- -d
- Turn on debugging information. In particular the command sent
to the remote host will be echoed.
- -h
- Print a usage message.
- -s
- Do not echo signals received by the rexec onto the remote
process. Normally, signals which can be trapped are passed on to
the remote process; then, when you type CNTRL-C, the remote process
terminates as well.
USERNAME AND PASSWORD
Rexec(1)
searches for the username and password in the following order:
- 1. If -n is given on the command line, the user will always be
prompted for both, even if they are also given on the command line.
- 2. The command line will be parsed
- 3. If the environmental variables REXEC_USER or REXEC_PASS are
defined, they will define the username or password.
- 4. The $HOME/.netrc file will be searched. See ftp(1) for a
description of this file's format.
- 5. Finally, the user will be prompted if either the username or
password remains undefined.
SECURITY
Users of this command should be aware that
transmits their password to the remote host clear text, not
encrypted. If the network is not secure to the remote host, the
password can be comprimised.
SIGNALS
Without the -b option, all signals which can be
handled are echoed to the remote process. Afterwards, however, they
remain raised in the local process. Typically, this means that
rexec(1)
will exit after receiving a fatal signal, even if the remote
process has arranged to handle or ignore it.
Differing operating systems use differing signal numbers; for
example AIX and SunOS use 18 for SIGTSTP (^Z), while Linux uses 20.
Therefore, it may have a different effect remotely than locally. In
particular, typing CNTL-Z may not suspend the execution of the
remote process.
EXAMPLE
rexec othermachine cat ">remote_file; date" <local_file
will send local_file to the othermachine as remote_file.
BUGS
Please send bug reports, system incompatibilities, and job
offers to the author.
SEE ALSO
rexec(3),
rexecd(8),
rsh(1)
AUTHOR
Michael Sadd
mas22@cornell.edu
http://www.tc.cornell.edu/~sadd/
Thanks to Orange Gopher (2/10/97) and Johannes Plass (plass@dipmza.physik.uni-mainz.de,
Oct. 17 1996) for useful suggestions.