Computer Science
REXEC(1) REXEC(1)
NAME
rexec -- remote execution client for an exec server
SYNOPSIS
rexec [ -abcdhns -l username -p password ] host command
DESCRIPTION
Rexec calls the rexec(3) 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 rexec(3) 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 stan-
dard input closes. Normally the standard input to
the remote command is closed when the local stan-
dard 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 termi-
nates 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 user-
name 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 rexec(3) trans-
mits 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 sig-
nal, 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
sadd@msc.cornell.edu
http://www.msc.cornell.edu/~sadd/
Thanks to Orange Gopher (2/10/97) and Johannes Plass
(plass@dipmza.physik.uni-mainz.de, Oct. 17 1996) for use-
ful suggestions.
February 14, 1997 1
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