rcmd(), rcmd_af()

Execute a command on a remote host

Synopsis:

#include <unistd.h>

int rcmd( char ** ahost, 
          unsigned short inport,
          const char * locuser,
          const char * remuser,
          const char * cmd, 
          int * fd2p );

int rcmd_af( char ** ahost, 
             unsigned short inport,
             const char * locuser,
             const char * remuser,
             const char * cmd, 
             int * fd2p,
             int af );

Arguments:

ahost

The name of the host that you want to execute the command on. If the function can find the host, it sets *ahost to the standard name of the host.

inport

The well-known Internet port on the host, where the server resides.

locuser

The user ID on the local machine.

remuser

The user ID on the remote machine.

cmd

The command that you want to execute.

fd2p

See below.

af

(rcmd_af() only) The address family; see <sys/socket.h>. If af is AF_UNSPEC or PF_UNSPEC, interpretation of *ahost obeys the underlying address resolution like DNS.

Library:

libsocket

Use the -l socket option to qcc to link against this library.

Description:

The rcmd() function is used by the superuser to execute a command, cmd, on a remote machine using an authentication scheme based on reserved port numbers. The rcmd() function can handle only IPv4 addresses as the first argument; rcmd_af() can handle other types of addresses as well. The rshd server (among others) uses the rcmd(), rresvport(), and ruserok() functions.

The rcmd() and rcmd_af() functions look up the host *ahost by means of gethostbyname(), and return -1 if the host doesn't exist. Otherwise, *ahost is set to the standard name of the host and a connection is established to a server residing at the well-known Internet port inport.

If the connection succeeds, a SOCK_STREAM socket in the Internet domain is returned to the caller and given to the remote command as standard input and standard output.

The protocol is described in detail in rshd in the Utilities Reference.

Returns:

A valid socket descriptor; or -1 if an error occurs and a message is printed to standard error.

Errors:

The error code EAGAIN is overloaded to mean “All network ports in use.”

Classification:

Unix

See also:

gethostbyname(), iruserok(), iruserok_sa(), rresvport(), ruserok()

rlogin, rlogind, rsh, rshd in the Utilities Reference