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36 .\" @(#)rcmd.3 8.1 (Berkeley) 6/4/93
38 .\" Contributed as Linux man page by David A. Holland, 970908
39 .\" I have not checked whether the Linux situation is exactly the same.
41 .\" 2007-12-08, mtk, Converted from mdoc to man macros
43 .TH RCMD 3 2014-05-28 "Linux" "Linux Programmer's Manual"
45 rcmd, rresvport, iruserok, ruserok, rcmd_af,
46 rresvport_af, iruserok_af, ruserok_af \- routines for returning a
47 stream to a remote command
50 .B #include <netdb.h> \ \ \fP/* Or <unistd.h> on some systems */
52 .BI "int rcmd(char **" ahost ", unsigned short " inport ", const char *" locuser ", "
53 .BI " const char *" remuser ", const char *" cmd ", int *" fd2p );
55 .BI "int rresvport(int *" port );
57 .BI "int iruserok(uint32_t " raddr ", int " superuser ", "
58 .BI " const char *" ruser ", const char *" luser );
60 .BI "int ruserok(const char *" rhost ", int " superuser ", "
61 .BI " const char *" ruser ", const char *" luser );
63 .BI "int rcmd_af(char **" ahost ", unsigned short " inport ", const char *" locuser ", "
64 .BI " const char *" remuser ", const char *" cmd ", int *" fd2p ,
65 .BI " sa_family_t " af );
67 .BI "int rresvport_af(int *" port ", sa_family_t " af );
69 .BI "int iruserok_af(const void *" raddr ", int " superuser ", "
70 .BI " const char *" ruser ", const char *" luser \
71 ", sa_family_t " af );
73 .BI "int ruserok_af(const char *" rhost ", int " superuser ", "
74 .BI " const char *" ruser ", const char *" luser \
75 ", sa_family_t " af );
79 Feature Test Macro Requirements for glibc (see
80 .BR feature_test_macros (7)):
95 function is used by the superuser to execute a command on
96 a remote machine using an authentication scheme based
97 on privileged port numbers.
101 returns a descriptor to a socket
102 with an address in the privileged port space.
107 functions are used by servers
108 to authenticate clients requesting service with
110 All four functions are used by the
112 server (among others).
121 .BR gethostbyname (3),
122 returning \-1 if the host does not exist.
125 is set to the standard name of the host
126 and a connection is established to a server
127 residing at the well-known Internet port
130 If the connection succeeds,
131 a socket in the Internet domain of type
133 is returned to the caller, and given to the remote
140 is nonzero, then an auxiliary channel to a control
141 process will be set up, and a descriptor for it will be placed
144 The control process will return diagnostic
145 output from the command (unit 2) on this channel, and will also
146 accept bytes on this channel as being UNIX signal numbers, to be
147 forwarded to the process group of the command.
152 (unit 2 of the remote
153 command) will be made the same as the
156 provision is made for sending arbitrary signals to the remote process,
157 although you may be able to get its attention by using out-of-band data.
159 The protocol is described in detail in
165 function is used to obtain a socket with a privileged
167 This socket is suitable for use by
169 and several other functions.
170 Privileged ports are those in the range 0 to 1023.
171 Only a privileged process
172 .RB ( CAP_NET_BIND_SERVICE )
173 is allowed to bind to a privileged port.
174 In the glibc implementation,
175 this function restricts its search to the ports from 512 to 1023.
178 argument is value-result:
179 the value it supplies to the call is used as the starting point
180 for a circular search of the port range;
181 on (successful) return, it contains the port number that was bound to.
183 .SS iruserok() and ruserok()
189 functions take a remote host's IP address or name, respectively,
190 two usernames and a flag indicating whether the local user's
191 name is that of the superuser.
194 the superuser, it checks the
197 If that lookup is not done, or is unsuccessful, the
199 in the local user's home directory is checked to see if the request for
202 If this file does not exist, is not a regular file, is owned by anyone
203 other than the user or the superuser, or is writable by anyone other
204 than the owner, the check automatically fails.
205 Zero is returned if the machine name is listed in the
207 file, or the host and remote username are found in the
214 If the local domain (as obtained from
216 is the same as the remote domain, only the machine name need be specified.
218 If the IP address of the remote host is known,
220 should be used in preference to
222 as it does not require trusting the DNS server for the remote host's domain.
224 All of the functions described above work with IPv4
227 The "_af" variants take an extra argument that allows the
228 socket address family to be specified.
229 For these functions, the
231 argument can be specified as
243 returns a valid socket descriptor on success.
244 It returns \-1 on error and prints a diagnostic message on the standard error.
249 returns a valid, bound socket descriptor on success.
250 It returns \-1 on error with the global value
252 set according to the reason for failure.
255 is overloaded to mean "All network ports in use."
257 For information on the return from
269 functions are provide in glibc since version 2.2.
272 Present on the BSDs, Solaris, and many other systems.
274 functions appeared in
276 The "_af" variants are more recent additions,
277 and are not present on as wide a range of systems.
282 are declared in glibc headers only since version 2.12.
283 .\" Bug filed 25 Nov 2007:
284 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=5399