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 user-
name/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 dae-
mons, or to debug connections:
-a Do not set up an auxiliary channel for standard error from com-
mand; 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 pro-
cess. 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 rexec(3) 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@dip-
mza.physik.uni-mainz.de, Oct. 17 1996) for useful suggestions.
February 14, 1997 REXEC(1)
