1.\" $OpenBSD: cu.1,v 1.21 2020/12/12 06:35:37 bentley Exp $ 2.\" 3.\" Copyright (c) 1980, 1990, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd $Mdocdate: December 12 2020 $ 31.Dt CU 1 32.Os 33.Sh NAME 34.Nm cu 35.Nd serial terminal emulator 36.Sh SYNOPSIS 37.Nm 38.Op Fl dr 39.Op Fl E Ar escape_char 40.Op Fl l Ar line 41.Op Fl s Ar speed | Fl Ar speed 42.Nm 43.Op Ar host 44.Sh DESCRIPTION 45.Nm 46is used to connect to another system over a serial link. 47In the era before modern networks, it was typically used to 48connect to a modem in order to dial in to a remote host. 49It is now frequently used for tasks such as attaching to the 50serial console of another machine for administrative or 51debugging purposes. 52.Pp 53The options are as follows: 54.Bl -tag -width 4n 55.It Fl d 56Specify that the line is directly connected and 57.Nm 58should not allow the driver to block waiting for a carrier to be detected. 59.It Fl E Ar escape_char 60Specify an escape character to use instead of the default tilde. 61.It Fl l Ar line 62Specify the line to use. 63Either of the forms like 64.Pa cua00 65or 66.Pa /dev/cua00 67are permitted. 68The default is 69.Pa /dev/cua00 . 70See 71.Xr cua 4 72for information on terminal devices. 73Users in group 74.Dq dialer 75are permitted to use 76.Xr cua 4 77devices by default. 78.It Fl r 79Start 80.Nm 81in restricted mode. 82This prevents all local filesystem operations 83.Po 84.Cm ~R , 85.Cm ~X , 86and 87.Cm ~> 88.Pc 89and command executions 90.Po 91.Cm ~C 92and 93.Cm ~$ 94.Pc . 95.It Fl s Ar speed | Fl Ar speed 96Set the speed of the connection. 97The default is 9600. 98.El 99.Pp 100If 101.Ar host 102is given, 103.Nm 104uses the 105.Xr remote 5 106database to retrieve the 107.Sy dc Pq directly connected , 108.Sy dv Pq device 109and 110.Sy br Pq baud rate 111capabilities for that host. 112The 113.Nm 114utility ignores other capabilities found in that database. 115.Pp 116Typed characters are normally transmitted directly to the remote 117machine (which does the echoing as well). 118A tilde 119.Pq Ql ~ 120appearing as the first character of a line is an escape signal; the 121following are recognized: 122.Bl -tag -offset indent -width Fl 123.It Ic ~^D No or Ic ~. 124Drop the connection and exit. 125Only the connection is dropped \(en the login session is not terminated. 126.It Ic ~> 127Copy file from local to remote. 128.Nm 129prompts for the name of a local file to transmit. 130.It Ic ~$ 131Pipe the output from a local 132.Ux 133process to the remote host. 134The command string sent to the local 135.Ux 136system is processed by the shell. 137.It Ic ~# 138Send a 139.Dv BREAK 140to the remote system. 141.It Ic ~^Z 142Stop 143.Nm 144(only available with job control). 145.It Ic ~C 146Fork a child process on the local system to perform special protocols 147such as XMODEM. 148The child program will be run with the following arrangement of 149file descriptors: 150.Pp 151.Bl -item -compact -offset indent 152.It 1530 \(<> remote tty in 154.It 1551 \(<> remote tty out 156.It 1572 \(<> local tty stderr 158.El 159.It Ic ~D 160Deassert the data terminal ready (DTR) line briefly. 161.It Ic ~R 162Record all output from the remote system to a file. 163If the given file already exists, it is appended to. 164If no file is specified, any existing recording is stopped. 165.It Ic ~S 166Change the speed of the connection. 167.It Ic ~X 168Send a file with the XMODEM protocol. 169.It Ic ~? 170Get a summary of the tilde escapes. 171.El 172.Pp 173When 174.Nm 175prompts for an argument, for example during setup of a file transfer, 176the line typed may be edited with the standard erase and kill characters. 177A null line in response to a prompt, or an interrupt, will abort the 178dialogue and return the user to the remote machine. 179.Pp 180.Nm 181guards against multiple users connecting to a remote system by opening 182modems and terminal lines with exclusive access. 183.Sh ENVIRONMENT 184.Bl -tag -width REMOTEXXX 185.It Ev HOST 186The default value for 187.Ar host 188if none is specified via the command line. 189.It Ev REMOTE 190A system description, or an absolute path to a 191.Xr remote 5 192system description database. 193.El 194.Sh FILES 195.Bl -tag -width /etc/remote 196.It Pa /etc/remote 197host description file 198.El 199.Sh EXIT STATUS 200.Ex -std cu 201.Sh SEE ALSO 202.Xr remote 5 203.Sh HISTORY 204The 205.Nm 206command appeared in 207.At v7 . 208This version was written for 209.Ox 5.4 210by Nicholas Marriott. 211