man3/rexec.3

   1 .\" Copyright (c) 1983, 1991, 1993
   2 .\"     The Regents of the University of California.  All rights reserved.
   3 .\"
   4 .\" SPDX-License-Identifier: BSD-4-Clause-UC
   5 .\"
   6 .\"     @(#)rexec.3     8.1 (Berkeley) 6/4/93
   7 .\" $FreeBSD: src/lib/libcompat/4.3/rexec.3,v 1.12 2004/07/02 23:52:14 ru Exp $
   8 .\"
   9 .\" Taken from FreeBSD 5.4; not checked against Linux reality (mtk)
  10 .\"
  11 .\" 2013-06-21, mtk, Converted from mdoc to man macros
  12 .\"
  13 .TH REXEC 3 2021-03-22 "Linux" "Linux Programmer's Manual"
  14 .SH NAME
  15 rexec, rexec_af \- return stream to a remote command
  16 .SH LIBRARY
  17 Standard C library
  18 .RI ( libc ", " \-lc )
  19 .SH SYNOPSIS
  20 .nf
  21 .B #include <netdb.h>
  22 .PP
  23 .BI "int rexec(char **restrict " ahost ", int " inport ,
  24 .BI "          const char *restrict " user ", const char *restrict " passwd ,
  25 .BI "          const char *restrict " cmd ", int *restrict " fd2p );
  26 .BI "int rexec_af(char **restrict " ahost ", int " inport ,
  27 .BI "          const char *restrict " user ", const char *restrict " passwd ,
  28 .BI "          const char *restrict " cmd ", int *restrict " fd2p ,
  29 .BI "          sa_family_t " af  );
  30 .fi
  31 .PP
  32 .BR rexec (),
  33 .BR rexec_af ():
  34 .nf
  35     Since glibc 2.19:
  36         _DEFAULT_SOURCE
  37     In glibc up to and including 2.19:
  38         _BSD_SOURCE
  39 .fi
  40 .SH DESCRIPTION
  41 This interface is obsoleted by
  42 .BR rcmd (3).
  43 .PP
  44 The
  45 .BR rexec ()
  46 function
  47 looks up the host
  48 .IR *ahost
  49 using
  50 .BR gethostbyname (3),
  51 returning \-1 if the host does not exist.
  52 Otherwise,
  53 .IR *ahost
  54 is set to the standard name of the host.
  55 If a username and password are both specified, then these
  56 are used to authenticate to the foreign host; otherwise
  57 the environment and then the
  58 .I .netrc
  59 file in user's
  60 home directory are searched for appropriate information.
  61 If all this fails, the user is prompted for the information.
  62 .PP
  63 The port
  64 .I inport
  65 specifies which well-known DARPA Internet port to use for
  66 the connection; the call
  67 .I "getservbyname(""exec"", ""tcp"")"
  68 (see
  69 .BR getservent (3))
  70 will return a pointer to a structure that contains the necessary port.
  71 The protocol for connection is described in detail in
  72 .BR rexecd (8).
  73 .PP
  74 If the connection succeeds,
  75 a socket in the Internet domain of type
  76 .BR SOCK_STREAM
  77 is returned to
  78 the caller, and given to the remote command as
  79 .IR stdin
  80 and
  81 .IR stdout .
  82 If
  83 .I fd2p
  84 is nonzero, then an auxiliary channel to a control
  85 process will be setup, and a file descriptor for it will be placed
  86 in
  87 .IR *fd2p .
  88 The control process will return diagnostic
  89 output from the command (unit 2) on this channel, and will also
  90 accept bytes on this channel as being UNIX signal numbers, to be
  91 forwarded to the process group of the command.
  92 The diagnostic
  93 information returned does not include remote authorization failure,
  94 as the secondary connection is set up after authorization has been
  95 verified.
  96 If
  97 .I fd2p
  98 is 0, then the
  99 .IR stderr
 100 (unit 2 of the remote
 101 command) will be made the same as the
 102 .IR stdout
 103 and no
 104 provision is made for sending arbitrary signals to the remote process,
 105 although you may be able to get its attention by using out-of-band data.
 106 .SS rexec_af()
 107 The
 108 .BR rexec ()
 109 function works over IPv4
 110 .RB ( AF_INET ).
 111 By contrast, the
 112 .BR rexec_af ()
 113 function provides an extra argument,
 114 .IR af ,
 115 that allows the caller to select the protocol.
 116 This argument can be specified as
 117 .BR AF_INET ,
 118 .BR AF_INET6 ,
 119 or
 120 .BR AF_UNSPEC
 121 (to allow the implementation to select the protocol).
 122 .SH VERSIONS
 123 The
 124 .BR rexec_af ()
 125 function was added to glibc in version 2.2.
 126 .SH ATTRIBUTES
 127 For an explanation of the terms used in this section, see
 128 .BR attributes (7).
 129 .ad l
 130 .nh
 131 .TS
 132 allbox;
 133 lbx lb lb
 134 l l l.
 135 Interface       Attribute       Value
 136 T{
 137 .BR rexec (),
 138 .BR rexec_af ()
 139 T}      Thread safety   MT-Unsafe
 140 .TE
 141 .hy
 142 .ad
 143 .sp 1
 144 .SH CONFORMING TO
 145 These functions are not in POSIX.1.
 146 The
 147 .BR rexec ()
 148 function first appeared in
 149 4.2BSD, and is present on the BSDs, Solaris, and many other systems.
 150 The
 151 .BR rexec_af ()
 152 function is more recent, and less widespread.
 153 .SH BUGS
 154 The
 155 .BR rexec ()
 156 function sends the unencrypted password across the network.
 157 .PP
 158 The underlying service is considered a big security hole and therefore
 159 not enabled on many sites; see
 160 .BR rexecd (8)
 161 for explanations.
 162 .SH SEE ALSO
 163 .BR rcmd (3),
 164 .BR rexecd (8)