HPUX rexec[3n]
rexec(3N) rexec(3N)
NAME
rexec() - return stream to a remote command
SYNOPSIS
int rexec(
char **ahost,
int inport,
const char *user,
const char *passwd,
const char *cmd,
int *fd2p);
DESCRIPTION
rexec() arranges for the remote execution of cmd on the host *ahost as
user, who is authenticated with passwd. It returns a file descriptor
for the socket to which the standard input and standard output of cmd
are attached. A command-level interface to rexec() is provided by the
rexec command (see remsh(1)).
rexec() looks up host *ahost using gethostbyname() (see
gethostbyname(3N)) and returns -1 if the host does not exist. The
host name can be either the official name or an alias. If the
gethostbyname() call succeeds, *ahost is set to the standard name of
the host. rexec() passes a username and password to the remote host
for authentication. These can be specified in the user and passwd
parameters to rexec(). If either is NULL, rexec() searches for the
appropriate information in the .netrc file (see netrc(4)) in the
users's home directory. If this fails, rexec() prompts the user for
the remote user name and password, defaulting to the local user name
and a NULL password.
inport specifies which TCP port to use for the connection; it is
normally the value returned by getservbyname("exec", "tcp") (see
getservent(3N)). The protocol used by rexec() is described in detail
in rexecd(1M).
If the call succeeds, a socket of type SOCK_STREAM is returned to the
caller, and given to the remote command as stdin and stdout. If the
connection to the socket is refused after five tries, or if it was
refused for a reason other than the port being in use, rexec() returns
-1. If fd2p is non-zero, an auxiliary connection to a control process
is set up and a file descriptor for it is placed in *fd2p. The
control process returns diagnostic output from the command on this
connection and accepts bytes on this connection, interpreting them as
UNIX signal numbers to be forwarded to the process group of the
command. If the auxiliary port cannot be set up, rexec() returns -1.
If fd2p is 0, stderr of the remote command is made the same as stdout
and no provision is made for sending arbitrary signals to the remote
process.
Hewlett-Packard Company - 1 - HP-UX Release 9.0: August 1992
rexec(3N) rexec(3N)
DIAGNOSTICS
rexec() produces the following diagnostic messages:
hostname: Unknown host
The remote host name was not found by gethostbyname().
system call:...
Error in executing the system call. A message specifying the
cause of the failure is appended to this message.
connect: hostname:...
Error in connecting to the socket obtained for rexec(). A
message specifying the cause of the failure is appended to this
diagnostic.
Secondary socket:...
Error in creating a secondary socket for error transmission to be
used by rexec().
read: hostname:...
Error in reading information transmitted over the socket. A
message specifying the cause of the failure is appended to this
diagnostic.
Connection timeout
The remote host did not connect within 30 seconds to the
secondary socket set up as an error connection.
Lost connection
The program attempts to read from the socket and fails. This
means the socket connection with the remote host was lost.
.netrc:...
Error in opening .netrc file in the home directory for a reason
other than the file not existing.
Error- .netrc file not correct mode.
Remove password or correct mode.
The .netrc file is readable, writable or executable by anyone
other than the user.
Next step: Check whether .netrc has been modified by someone else
and change the mode of .netrc (chmod 400 .netrc).
Unknown .netrc option ...
An unrecognized keyword has been found in .netrc (see netrc(4)).
Next step: Correct keyword in .netrc.
Hewlett-Packard Company - 2 - HP-UX Release 9.0: August 1992
rexec(3N) rexec(3N)
primary connection shutdown
While waiting for the secondary socket to be set up, rexec() had
its primary connection shut down. This may have been caused by
the inetd security failure.
recv:...
While trying to set up the secondary (stderr) socket, rexec() had
an error condition on its primary connection.
accept: Interrupted system call
While trying to set up a secondary socket, rexec() ran out of a
resource, which caused the accept to be timed out.
Next step: Repeat the command. If a timeout occurs, check whether
the ARPA Services are installed and inetd is running.
EXAMPLE
To execute the date command on remote host hpxzgy using the remote
account chm, rexec() could be used as follows:
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
char *host[] = { "hpxzgy" };
char *user = "chm";
char *passwd = "password";
char *cmd = "date";
main(argc, argv)
char **argv;
int argc;
{
char ch;
struct servent *servent;
FILE *fp;
int sd;
servent = getservbyname("exec", "tcp");
sd = rexec(host, servent->s_port, user, passwd, cmd, 0);
fp = fdopen(sd, "r");
while ((ch = getc(fp)) != EOF)
putchar(ch);
}
WARNINGS
There is no way to specify options to the socket() call that rexec()
makes.
Hewlett-Packard Company - 3 - HP-UX Release 9.0: August 1992
rexec(3N) rexec(3N)
A program using rexec() should not be put in the background when
rexec() is expected to prompt for a password or user name. If it is
put in the background it will compete with the shell for input.
Since rexec() replaces the pointer to the hostname (*ahost) with a
pointer to the standard name of the host in a static data area, this
value must be copied into the user's data area if it is to be used
later.
The password is sent unencrypted through the socket connection.
AUTHOR
rexec() was developed by the University of California, Berkeley.
SEE ALSO
remsh(1), rexecd(1M), gethostent(3N), getservent(3N), rcmd(3N),
netrc(4).
Hewlett-Packard Company - 4 - HP-UX Release 9.0: August 1992