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The r-commands were a significant innovation, and became ''de facto'' standards for Unix operating systems.<ref>Casad (2008), p. [https://books.google.com/books?id=q81cs5140_YC&pg=PT346 346]</ref><ref>{{cite book |title=Red Hat Fedora Linux 2 Bible |last=Negus |first=Christopher |publisher=Wiley |isbn=0-7645-5745-9 |oclc=441918216 |chapter=About "r" Commands |chapter-url=https://www.wiley.com/legacy/compbooks/negus/rhbf2/r-commands.html |access-date=2018-03-04}}</ref>
==
{| class="wikitable" style="clear:right; float:right; text-align:center; margin-left:3ex"
|+ Overview
! scope="col" colspan="2" | Service !! scope="col" rowspan="2" | [[Port (computer networking)|Port]] !! scope="col" rowspan="2" | [[Transport protocol|Transport]] || scope="col" rowspan="2" | {{abbr|Refs|References}}
|-
! scope="col" | [[Client (computing)|Client]] !! scope="col" | [[Daemon (computer software)|Daemon]]
|-
| style="text-align:left" | rcp || || 514 || TCP ||
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| style="text-align:left" | rwho || <ref name="NAG"/><ref name="Casad-350"/>
|}
{{Expand section|date=March 2018}}
The original Berkeley package that provides rlogin also features rcp (remote-copy, allowing files to be copied over the network) and [[Remote Shell|rsh]] (remote-shell, allowing commands to be run on a remote machine without the user logging into it).
==Commands==
===rlogin===
{{See also|Telnet}}
{{code|rlogin}} enables a user to log in on another [[Server (computing)|server]] via [[computer network]], using [[Transmission Control Protocol|TCP]] [[network port]] 513.
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rlogin is also the name of the [[application layer]] [[Communications protocol|protocol]] used by the software, part of the [[TCP/IP]] [[protocol suite]]. Authenticated users can act as if they were physically present at the computer. RFC 1282, in which it was defined, states: "The rlogin facility provides a remote-echoed, locally flow-controlled virtual terminal with proper flushing of output." rlogin communicates with a [[daemon (computer software)|daemon]], rlogind, on the remote host. rlogin is similar to the [[Telnet]] command, but is not as customizable and is able to connect only to Unix-like hosts.
==
{{Further|Remote Shell}}
rsh opens a [[Shell (computing)|shell]] on a remote computer without a [[login]] procedure. Once connected, the user can execute commands on the remote computer through the shell's [[command-line interface]]. rsh passes input and output through the [[standard streams]], and it sends [[standard output]] to the user's [[Virtual console|console]]. Over the network, [[standard input]] and standard out flow through TCP port 514, while [[standard error]] flows through a different TCP port, which the rsh [[Daemon (computing)|daemon]] (rshd) opens.<ref>{{cite book |url=https://books.google.com/books?id=-hF7sqwrcrwC&pg=PA154 |title=CCSP: Secure PIX and Secure VPN Study Guide |last=Edwards |first=Wade |last2=Lancaster |first2=Tom |last3=Quinn |first3=Eric |last4=Rohm |first4=Jason |last5=Tow |first5=Bryant|publisher=[[Sybex]] |page=154 |isbn=0-7821-4287-7 |year=2004 |via=Google Books |access-date=2018-03-07}}</ref>
▲The original Berkeley package that provides rlogin also features rcp (remote-copy, allowing files to be copied over the network) and [[Remote Shell|rsh]] (remote-shell, allowing commands to be run on a remote machine without the user logging into it). These share the hosts.equiv and .rhosts access-control scheme (although they connect to a different daemon, rshd), and as such suffer from the same security exposures.
===rexec===
Like rsh, rexec enables the user to run shell commands on a remote computer. However, unlike the rsh server, the rexec server (rexecd) requires login: it authenticates users by reading the username and password (unencrypted) from the [[network socket]].<ref>{{cite web |url=http://www.manpagez.com/man/8/rexecd/ |title=rexecd(8) |website=manpagez.com |access-date=2018-03-03}}</ref> rexec uses TCP port 512.
===rcp===▼
▲==rcp==
rcp can copy a file or directory from the local system to a remote system, from a remote system to the local system, or from one remote system to another.<ref name="Farrell">{{cite web |url=https://earthsci.stanford.edu/computing/unix/netcommands/rcp.php |title=rcp |last=Farrell |first=Phillip |date=3 August 2004 |website=earthsci.stanford.edu |publisher=Stanford University School of Earth, Energy & Environmental Sciences |access-date=2018-03-06}}</ref> The command line [[Parameter (computer programming)|arguments]] of cp and rcp are similar, but in rcp remote files are prefixed with the name of the remote system:
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As with the Unix copy command [[cp (Unix)|cp]], rcp overwrites an existing file of the same name in the target; unlike cp, it provides no mechanism for warning the user before overwriting the target file.<ref name="Farrell"/> Like rsh, rcp uses TCP port 514.<ref>{{cite web |url=http://sourcedaddy.com/networking/rlogin-rsh-and-rcp.html |title=Rlogin, RSH, and RCP |website=SourceDaddy |access-date=2018-02-18}}</ref>
===rwho===
Just as the [[who (Unix)|who]] command lists the users who are logged in to the local Unix system, rwho lists those users who are logged into all [[multi-user]] Unix systems on the local network.<ref name="syst_rwhod">{{cite web |url=https://www.systutorials.com/docs/linux/man/1-rwho/ |title=rwho (1) - Linux Man Pages |access-date=2018-03-07}}</ref> rwho's daemon, rwhod, maintains a database of the status of Unix systems on the local network. The daemon and its database are also used by the ruptime program.<ref name="syst_rwhod">{{cite web |url=https://www.systutorials.com/docs/linux/man/8-rwhod/ |title=rwhod (8) - Linux Man Pages |access-date=2018-03-07}}</ref>
===rstat===
{{empty section|date=March 2018}}
===ruptime===
Just as the {{code|uptime}} command shows how long a Unix system has been running since the last restart, {{code|ruptime}} requests a status report from all computers on the local network. It then returns the uptime report. If a computer did not respond within the time limit, then ruptime reports that the system is [[Downtime|down]].<ref>{{cite web |url=https://www.systutorials.com/docs/linux/man/1-ruptime/ |title=ruptime (1) - Linux Man Pages |website=SysTutorials |access-date=2018-03-07}}</ref> This information is tracked and stored by the daemon rwhod, which is also used by the rwho command.<ref name="syst_rwhod"/>
== See also ==
* [[List of Unix commands]]
* [[Secure Shell]]
==Notes==
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