rexec(3)

NAME

   rexec, rexec_af - return stream to a remote command

SYNOPSIS

   #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);

   rexec(), rexec_af():
       Since glibc 2.19:
           _DEFAULT_SOURCE
       In glibc up to and including 2.19:
           _BSD_SOURCE

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  foreign  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 file 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 connection
   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  provides  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

   For  an  explanation  of  the  terms  used   in   this   section,   see
   attributes(7).

   
   Interface            Attribute      Value     
   
   rexec(), rexec_af()  Thread safety  MT-Unsafe 
   

CONFORMING TO

   These  functions  are  not  in  POSIX.1.   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 4.09 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
   https://www.kernel.org/doc/man-pages/.

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