rexec(3) — Linux manual page


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

NAME         top

       rexec, rexec_af - return stream to a remote command

SYNOPSIS         top

       #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:
           In glibc up to and including 2.19:

DESCRIPTION         top

       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.

       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         top

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

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

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

CONFORMING TO         top

       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

BUGS         top

       The rexec() function sends the unencrypted password across the

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

SEE ALSO         top

       rcmd(3), rexecd(8)

COLOPHON         top

       This page is part of release 5.08 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

Linux                            2017-09-15                         REXEC(3)

Pages that refer to this page: iruserok(3)iruserok_af(3)rcmd(3)rcmd_af(3)rresvport(3)rresvport_af(3)ruserok(3)ruserok_af(3)