1tset(1) General Commands Manual tset(1)
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6 tset, reset - terminal initialization
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9 tset [-IQVcqrsw] [-] [-e ch] [-i ch] [-k ch] [-m mapping] [terminal]
10 reset [-IQVcqrsw] [-] [-e ch] [-i ch] [-k ch] [-m mapping] [terminal]
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13 tset - initialization
14 This program initializes terminals.
15 First, tset retrieves the current terminal mode settings for your ter‐
17 minal. It does this by successively testing
18 • the standard error,
20 • standard output,
22 • standard input and
24 • ultimately “/dev/tty”
26 to obtain terminal settings. Having retrieved these settings, tset re‐
28 members which file descriptor to use when updating settings.
29 Next, tset determines the type of terminal that you are using. This
31 determination is done as follows, using the first terminal type found.
32 1. The terminal argument specified on the command line.
34 2. The value of the TERM environmental variable.
36 3. (BSD systems only.) The terminal type associated with the standard
38 error output device in the /etc/ttys file. (On System-V-like UNIXes
39 and systems using that convention, getty(1) does this job by setting
40 TERM according to the type passed to it by /etc/inittab.)
41 4. The default terminal type, “unknown”.
43 If the terminal type was not specified on the command-line, the -m op‐
45 tion mappings are then applied (see the section TERMINAL TYPE MAPPING
46 for more information). Then, if the terminal type begins with a ques‐
47 tion mark (“?”), the user is prompted for confirmation of the terminal
48 type. An empty response confirms the type, or, another type can be en‐
49 tered to specify a new type. Once the terminal type has been deter‐
50 mined, the terminal description for the terminal is retrieved. If no
51 terminal description is found for the type, the user is prompted for
52 another terminal type.
53 Once the terminal description is retrieved,
55 • if the “-w” option is enabled, tset may update the terminal's win‐
57 dow size.
58 If the window size cannot be obtained from the operating system,
60 but the terminal description (or environment, e.g., LINES and COL‐
61 UMNS variables specify this), use this to set the operating sys‐
62 tem's notion of the window size.
63 • if the “-c” option is enabled, the backspace, interrupt and line
65 kill characters (among many other things) are set
66 • unless the “-I” option is enabled, the terminal and tab initializa‐
68 tion strings are sent to the standard error output, and tset waits
69 one second (in case a hardware reset was issued).
70 • Finally, if the erase, interrupt and line kill characters have
72 changed, or are not set to their default values, their values are
73 displayed to the standard error output.
74 reset - reinitialization
76 When invoked as reset, tset sets the terminal modes to “sane” values:
77 • sets cooked and echo modes,
79 • turns off cbreak and raw modes,
81 • turns on newline translation and
83 • resets any unset special characters to their default values
85 before doing the terminal initialization described above. Also, rather
87 than using the terminal initialization strings, it uses the terminal
88 reset strings.
89 The reset command is useful after a program dies leaving a terminal in
91 an abnormal state:
92 • you may have to type
94 <LF>reset<LF>
96 (the line-feed character is normally control-J) to get the terminal
98 to work, as carriage-return may no longer work in the abnormal
99 state.
100 • Also, the terminal will often not echo the command.
102
104 The options are as follows:
105 -c Set control characters and modes.
107 -e ch
109 Set the erase character to ch.
110 -I Do not send the terminal or tab initialization strings to the ter‐
112 minal.
113 -i ch
115 Set the interrupt character to ch.
116 -k ch
118 Set the line kill character to ch.
119 -m mapping
121 Specify a mapping from a port type to a terminal. See the section
122 TERMINAL TYPE MAPPING for more information.
123 -Q Do not display any values for the erase, interrupt and line kill
125 characters. Normally tset displays the values for control charac‐
126 ters which differ from the system's default values.
127 -q The terminal type is displayed to the standard output, and the
129 terminal is not initialized in any way. The option “-” by itself
130 is equivalent but archaic.
131 -r Print the terminal type to the standard error output.
133 -s Print the sequence of shell commands to initialize the environment
135 variable TERM to the standard output. See the section SETTING THE
136 ENVIRONMENT for details.
137 -V reports the version of ncurses which was used in this program, and
139 exits.
140 -w Resize the window to match the size deduced via setupterm(3X).
142 Normally this has no effect, unless setupterm is not able to de‐
143 tect the window size.
144 The arguments for the -e, -i, and -k options may either be entered as
146 actual characters or by using the “hat” notation, i.e., control-h may
147 be specified as “^H” or “^h”.
148 If neither -c or -w is given, both options are assumed.
150
152 It is often desirable to enter the terminal type and information about
153 the terminal's capabilities into the shell's environment. This is done
154 using the -s option.
155 When the -s option is specified, the commands to enter the information
157 into the shell's environment are written to the standard output. If
158 the SHELL environmental variable ends in “csh”, the commands are for
159 csh, otherwise, they are for sh(1). Note, the csh commands set and un‐
160 set the shell variable noglob, leaving it unset. The following line in
161 the .login or .profile files will initialize the environment correctly:
162 eval `tset -s options ... `
164
166 When the terminal is not hardwired into the system (or the current sys‐
167 tem information is incorrect) the terminal type derived from the
168 /etc/ttys file or the TERM environmental variable is often something
169 generic like network, dialup, or unknown. When tset is used in a
170 startup script it is often desirable to provide information about the
171 type of terminal used on such ports.
172 The -m options maps from some set of conditions to a terminal type,
174 that is, to tell tset “If I'm on this port at a particular speed, guess
175 that I'm on that kind of terminal”.
176 The argument to the -m option consists of an optional port type, an op‐
178 tional operator, an optional baud rate specification, an optional colon
179 (“:”) character and a terminal type. The port type is a string (delim‐
180 ited by either the operator or the colon character). The operator may
181 be any combination of “>”, “<”, “@”, and “!”; “>” means greater than,
182 “<” means less than, “@” means equal to and “!” inverts the sense of
183 the test. The baud rate is specified as a number and is compared with
184 the speed of the standard error output (which should be the control
185 terminal). The terminal type is a string.
186 If the terminal type is not specified on the command line, the -m map‐
188 pings are applied to the terminal type. If the port type and baud rate
189 match the mapping, the terminal type specified in the mapping replaces
190 the current type. If more than one mapping is specified, the first ap‐
191 plicable mapping is used.
192 For example, consider the following mapping: dialup>9600:vt100. The
194 port type is dialup , the operator is >, the baud rate specification is
195 9600, and the terminal type is vt100. The result of this mapping is to
196 specify that if the terminal type is dialup, and the baud rate is
197 greater than 9600 baud, a terminal type of vt100 will be used.
198 If no baud rate is specified, the terminal type will match any baud
200 rate. If no port type is specified, the terminal type will match any
201 port type. For example, -m dialup:vt100 -m :?xterm will cause any di‐
202 alup port, regardless of baud rate, to match the terminal type vt100,
203 and any non-dialup port type to match the terminal type ?xterm. Note,
204 because of the leading question mark, the user will be queried on a de‐
205 fault port as to whether they are actually using an xterm terminal.
206 No whitespace characters are permitted in the -m option argument.
208 Also, to avoid problems with meta-characters, it is suggested that the
209 entire -m option argument be placed within single quote characters, and
210 that csh users insert a backslash character (“\”) before any exclama‐
211 tion marks (“!”).
212
214 A reset command appeared in 1BSD (March 1978), written by Kurt Shoens.
215 This program set the erase and kill characters to ^H (backspace) and @
216 respectively. Mark Horton improved that in 3BSD (October 1979), adding
217 intr, quit, start/stop and eof characters as well as changing the pro‐
218 gram to avoid modifying any user settings. That version of reset did
219 not use the termcap database.
220 A separate tset command was provided in 1BSD by Eric Allman, using the
222 termcap database. Allman's comments in the source code indicate that
223 he began work in October 1977, continuing development over the next few
224 years.
225 According to comments in the source code, the tset program was modified
227 in September 1980, to use logic copied from the 3BSD “reset” when it
228 was invoked as reset. This version appeared in 4.1cBSD, late in 1982.
229 Other developers (e.g., Keith Bostic and Jim Bloom) continued to modify
231 tset until 4.4BSD was released in 1993.
232 The ncurses implementation was lightly adapted from the 4.4BSD sources
234 for a terminfo environment by Eric S. Raymond <esr@snark.thyrsus.com>.
235
237 Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7
238 (POSIX.1-2008) nor X/Open Curses Issue 7 documents tset or reset.
239 The AT&T tput utility (AIX, HPUX, Solaris) incorporated the terminal-
241 mode manipulation as well as termcap-based features such as resetting
242 tabstops from tset in BSD (4.1c), presumably with the intention of mak‐
243 ing tset obsolete. However, each of those systems still provides tset.
244 In fact, the commonly-used reset utility is always an alias for tset.
245 The tset utility provides for backward-compatibility with BSD environ‐
247 ments (under most modern UNIXes, /etc/inittab and getty(1) can set TERM
248 appropriately for each dial-up line; this obviates what was tset's most
249 important use). This implementation behaves like 4.4BSD tset, with a
250 few exceptions specified here.
251 A few options are different because the TERMCAP variable is no longer
253 supported under terminfo-based ncurses:
254 • The -S option of BSD tset no longer works; it prints an error mes‐
256 sage to the standard error and dies.
257 • The -s option only sets TERM, not TERMCAP.
259 There was an undocumented 4.4BSD feature that invoking tset via a link
261 named “TSET” (or via any other name beginning with an upper-case let‐
262 ter) set the terminal to use upper-case only. This feature has been
263 omitted.
264 The -A, -E, -h, -u and -v options were deleted from the tset utility in
266 4.4BSD. None of them were documented in 4.3BSD and all are of limited
267 utility at best. The -a, -d, and -p options are similarly not docu‐
268 mented or useful, but were retained as they appear to be in widespread
269 use. It is strongly recommended that any usage of these three options
270 be changed to use the -m option instead. The -a, -d, and -p options
271 are therefore omitted from the usage summary above.
272 Very old systems, e.g., 3BSD, used a different terminal driver which
274 was replaced in 4BSD in the early 1980s. To accommodate these older
275 systems, the 4BSD tset provided a -n option to specify that the new
276 terminal driver should be used. This implementation does not provide
277 that choice.
278 It is still permissible to specify the -e, -i, and -k options without
280 arguments, although it is strongly recommended that such usage be fixed
281 to explicitly specify the character.
282 As of 4.4BSD, executing tset as reset no longer implies the -Q option.
284 Also, the interaction between the - option and the terminal argument in
285 some historic implementations of tset has been removed.
286 The -c and -w options are not found in earlier implementations. How‐
288 ever, a different window size-change feature was provided in 4.4BSD.
289 • In 4.4BSD, tset uses the window size from the termcap description
291 to set the window size if tset is not able to obtain the window
292 size from the operating system.
293 • In ncurses, tset obtains the window size using setupterm, which may
295 be from the operating system, the LINES and COLUMNS environment
296 variables or the terminal description.
297 Obtaining the window size from the terminal description is common to
299 both implementations, but considered obsolescent. Its only practical
300 use is for hardware terminals. Generally speaking, a window size would
301 be unset only if there were some problem obtaining the value from the
302 operating system (and setupterm would still fail). For that reason,
303 the LINES and COLUMNS environment variables may be useful for working
304 around window-size problems. Those have the drawback that if the win‐
305 dow is resized, those variables must be recomputed and reassigned. To
306 do this more easily, use the resize(1) program.
307
309 The tset command uses these environment variables:
310 SHELL
312 tells tset whether to initialize TERM using sh(1) or csh(1) syn‐
313 tax.
314 TERM Denotes your terminal type. Each terminal type is distinct,
316 though many are similar.
317 TERMCAP
319 may denote the location of a termcap database. If it is not an
320 absolute pathname, e.g., begins with a “/”, tset removes the vari‐
321 able from the environment before looking for the terminal descrip‐
322 tion.
323
325 /etc/ttys
326 system port name to terminal type mapping database (BSD versions
327 only).
328 /usr/share/terminfo
330 terminal capability database
331
333 csh(1), sh(1), stty(1), curs_terminfo(3X), tty(4), terminfo(5),
334 ttys(5), environ(7)
335 This describes ncurses version 6.4 (patch 20230114).
337 tset(1)