REXEC(3)                            Linux Programmer's Manual                            REXEC(3)



NAME
       rexec, rexec_af - return stream to a remote command

SYNOPSIS
       #define _BSD_SOURCE             /* See feature_test_macros(7) */
       #include <netdb.h>

       int rexec(char **ahost, int inport, const char *user,
                 const char *passwd, const char *cmd, int *fd2p);

       int rexec_af(char **ahost, int inport, const char *user,
                    const char *passwd, const char *cmd, int *fd2p,
                    sa_family_t af);

DESCRIPTION
       This interface is obsoleted by rcmd(3).

       The  rexec() function looks up the host *ahost using gethostbyname(3), returning -1 if the
       host does not exist.  Otherwise, *ahost is set to the standard name of  the  host.   If  a
       username  and password are both specified, then these are used to authenticate to the for‐
       eign host; otherwise the environment and then the .netrc file in user's home directory are
       searched  for  appropriate  information.   If all this fails, the user is prompted for the
       information.

       The port inport specifies which well-known DARPA Internet port to use for the  connection;
       the  call  getservbyname("exec",  "tcp")  (see  getservent(3))  will return a pointer to a
       structure that contains the necessary port.  The protocol for connection is  described  in
       detail in rexecd(8).

       If  the  connection  succeeds,  a  socket  in  the  Internet domain of type SOCK_STREAM is
       returned to the caller, and given to the remote command as stdin and stdout.  If  fd2p  is
       nonzero,  then  an  auxiliary channel to a control process will be setup, and a descriptor
       for it will be placed in *fd2p.  The control process will return  diagnostic  output  from
       the  command (unit 2) on this channel, and will also accept bytes on this channel as being
       UNIX signal numbers, to be forwarded to the process group of the command.  The  diagnostic
       information  returned does not include remote authorization failure, as the secondary con‐
       nection is set up after authorization has been verified.  If fd2p is 0,  then  the  stderr
       (unit  2  of  the  remote command) will be made the same as the stdout and no provision is
       made for sending arbitrary signals to the remote process, although you may be able to  get
       its attention by using out-of-band data.

   rexec_af()
       The rexec() function works over IPv4 (AF_INET).  By contrast, the rexec_af() function pro‐
       vides an extra argument, af, that allows the caller to select the protocol.  This argument
       can be specified as AF_INET, AF_INET6, or AF_UNSPEC (to allow the implementation to select
       the protocol).

VERSIONS
       The rexec_af() function was added to glibc in version 2.2.

ATTRIBUTES
   Multithreading (see pthreads(7))
       The rexec() and rexec_af() functions are not thread-safe.

CONFORMING TO
       These functions are not in POSIX.1-2001.  The rexec() function first appeared  in  4.2BSD,
       and  is  present on the BSDs, Solaris, and many other systems.  The rexec_af() function is
       more recent, and less widespread.

BUGS
       The rexec() function sends the unencrypted password across the network.

       The underlying service is considered a big security hole and therefore not enabled on many
       sites; see rexecd(8) for explanations.

SEE ALSO
       rcmd(3), rexecd(8)

COLOPHON
       This  page  is  part of release 3.74 of the Linux man-pages project.  A description of the
       project, information about reporting bugs, and the latest version of  this  page,  can  be
       found at http://www.kernel.org/doc/man-pages/.



Linux                                       2014-05-28                                   REXEC(3)