man3/rexec.3

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  34 .\"     @(#)rexec.3     8.1 (Berkeley) 6/4/93
  35 .\" $FreeBSD: src/lib/libcompat/4.3/rexec.3,v 1.12 2004/07/02 23:52:14 ru Exp $
  36 .\"
  37 .\" Taken from FreeBSD 5.4; not checked against Linux reality (mtk)
  38 .\"
  39 .\" 2013-06-21, mtk, Converted from mdoc to man macros
  40 .\"
  41 .TH REXEC 3 2017-09-15 "Linux" "Linux Programmer's Manual"
  42 .SH NAME
  43 rexec, rexec_af \- return stream to a remote command
  44 .SH SYNOPSIS
  45 .nf
  46 .B #include <netdb.h>
  47 .PP
  48 .BI "int rexec(char **" ahost ", int " inport ", const char *" user ", "
  49 .BI "          const char *" passwd ", const char *" cmd ", int *" fd2p );
  50 .PP
  51 .BI "int rexec_af(char **" ahost ", int " inport ", const char *" user ", "
  52 .BI "             const char *" passwd ", const char *" cmd ", int *" fd2p ,
  53 .BI "             sa_family_t " af  );
  54 .fi
  55 .PP
  56 .BR rexec (),
  57 .BR rexec_af ():
  58 .nf
  59     Since glibc 2.19:
  60         _DEFAULT_SOURCE
  61     In glibc up to and including 2.19:
  62         _BSD_SOURCE
  63 .fi
  64 .SH DESCRIPTION
  65 This interface is obsoleted by
  66 .BR rcmd (3).
  67 .PP
  68 The
  69 .BR rexec ()
  70 function
  71 looks up the host
  72 .IR *ahost
  73 using
  74 .BR gethostbyname (3),
  75 returning \-1 if the host does not exist.
  76 Otherwise,
  77 .IR *ahost
  78 is set to the standard name of the host.
  79 If a username and password are both specified, then these
  80 are used to authenticate to the foreign host; otherwise
  81 the environment and then the
  82 .I .netrc
  83 file in user's
  84 home directory are searched for appropriate information.
  85 If all this fails, the user is prompted for the information.
  86 .PP
  87 The port
  88 .I inport
  89 specifies which well-known DARPA Internet port to use for
  90 the connection; the call
  91 .I "getservbyname(""exec"", ""tcp"")"
  92 (see
  93 .BR getservent (3))
  94 will return a pointer to a structure that contains the necessary port.
  95 The protocol for connection is described in detail in
  96 .BR rexecd (8).
  97 .PP
  98 If the connection succeeds,
  99 a socket in the Internet domain of type
 100 .BR SOCK_STREAM
 101 is returned to
 102 the caller, and given to the remote command as
 103 .IR stdin
 104 and
 105 .IR stdout .
 106 If
 107 .I fd2p
 108 is nonzero, then an auxiliary channel to a control
 109 process will be setup, and a file descriptor for it will be placed
 110 in
 111 .IR *fd2p .
 112 The control process will return diagnostic
 113 output from the command (unit 2) on this channel, and will also
 114 accept bytes on this channel as being UNIX signal numbers, to be
 115 forwarded to the process group of the command.
 116 The diagnostic
 117 information returned does not include remote authorization failure,
 118 as the secondary connection is set up after authorization has been
 119 verified.
 120 If
 121 .I fd2p
 122 is 0, then the
 123 .IR stderr
 124 (unit 2 of the remote
 125 command) will be made the same as the
 126 .IR stdout
 127 and no
 128 provision is made for sending arbitrary signals to the remote process,
 129 although you may be able to get its attention by using out-of-band data.
 130 .SS rexec_af()
 131 The
 132 .BR rexec ()
 133 function works over IPv4
 134 .RB ( AF_INET ).
 135 By contrast, the
 136 .BR rexec_af ()
 137 function provides an extra argument,
 138 .IR af ,
 139 that allows the caller to select the protocol.
 140 This argument can be specified as
 141 .BR AF_INET ,
 142 .BR AF_INET6 ,
 143 or
 144 .BR AF_UNSPEC
 145 (to allow the implementation to select the protocol).
 146 .SH VERSIONS
 147 The
 148 .BR rexec_af ()
 149 function was added to glibc in version 2.2.
 150 .SH ATTRIBUTES
 151 For an explanation of the terms used in this section, see
 152 .BR attributes (7).
 153 .TS
 154 allbox;
 155 lbw19 lb lb
 156 l l l.
 157 Interface       Attribute       Value
 158 T{
 159 .BR rexec (),
 160 .BR rexec_af ()
 161 T}      Thread safety   MT-Unsafe
 162 .TE
 163 .SH CONFORMING TO
 164 These functions are not in POSIX.1.
 165 The
 166 .BR rexec ()
 167 function first appeared in
 168 4.2BSD, and is present on the BSDs, Solaris, and many other systems.
 169 The
 170 .BR rexec_af ()
 171 function is more recent, and less widespread.
 172 .SH BUGS
 173 The
 174 .BR rexec ()
 175 function sends the unencrypted password across the network.
 176 .PP
 177 The underlying service is considered a big security hole and therefore
 178 not enabled on many sites; see
 179 .BR rexecd (8)
 180 for explanations.
 181 .SH SEE ALSO
 182 .BR rcmd (3),
 183 .BR rexecd (8)